|
Record 1 of 38 |
|
Title: C/NOFS: a mission to forecast scintillations |
|
Author(s): de La Beaujardiere, O (de La Beaujardiere, O) |
|
Group Author(s): CNOFS Science Definition Team |
|
Source: JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS Volume: 66 Issue: 17 Pages: 1573-1591 DOI: 10.1016/j.jastp.2004.07.030 Published: NOV 2004 |
|
Times Cited in Web of Science: 66 |
|
Total Times Cited: 66 |
|
Abstract: This article describes the science to be pursued
during the Communication/Navigation Outage Forecasting System (C/NOFS)
Mission of the Air Force Research Laboratory. The primary purpose of C/NOFS
is to forecast the presence of ionospheric irregularities that adversely
impact communication and navigation systems. A satellite, scheduled for
launch in May 2005 into a low inclination (13degrees), elliptical (similar to
375 x 710 km) orbit, is the most significant component of the C/NOFS program.
Complementary ground-based measurements are also critical to the success of
the mission. |
|
Accession Number: WOS:000225051000007 |
|
Conference Title: Jicamarca 40th Anniversary Workshop |
|
Conference Date: MAY, 2002 |
|
Conference Location: Jicamarca, PERU |
|
ISSN: 1364-6826 |
|
Record 2 of 38 |
|
Title: Comparing F region ionospheric irregularity observations from C/NOFS and Jicamarca |
|
Author(s): Hysell, DL (Hysell, D. L.); Hedden, RB (Hedden, R. B.); Chau, JL (Chau, J. L.); Galindo, FR (Galindo, F. R.); Roddy, PA (Roddy, P. A.); Pfaff, RF (Pfaff, R. F.) |
|
Source: GEOPHYSICAL RESEARCH LETTERS Volume: 36 Article Number: L00C01 DOI: 10.1029/2009GL038983 Published: JUL 11 2009 |
|
Times Cited in Web of Science: 2 |
|
Total Times Cited: 2 |
|
Abstract: Observations of plasma density irregularities associated with equatorial spread F (ESF) have been made using the Jicamarca Radio Observatory and the Plasma Langmuir Probe (PLP) and Vector Electric Field Instrument (VEFI) instruments on the Communications Navigation Outage Forecast System (C/NOFS) satellite during a close spatio-temporal conjunction. The radar data resolution is of the order of 1 km and a few sec. in space and time, respectively. We find that coherent scatter intensifications at these scales are coincident and collocated with plasma density depletions as determined by C/NOFS. The Doppler shifts of the localized echoes are also comparable to the vertical components of the E x B plasma drifts. The strongest backscatter does not necessarily come from the deepest or most rapidly convecting depletions. This implies a complex relationship between coherent backscatter and the underlying state parameters in the ionospheric plasma. Citation: Hysell, D. L., R. B. Hedden, J. L. Chau, F. R. Galindo, P. A. Roddy, and R. F. Pfaff (2009), Comparing F region ionospheric irregularity observations from C/NOFS and Jicamarca, Geophys. Res. Lett., 36, L00C01, doi:10.1029/2009GL038983. |
|
Accession Number: WOS:000267935500005 |
|
ISSN: 0094-8276 |
|
Record 3 of 38 |
|
Title: Assimilative modeling of equatorial plasma depletions observed by C/NOFS |
|
Author(s): Su, YJ (Su, Y. -J.); Retterer, JM (Retterer, J. M.); de La Beaujardiere, O (de La Beaujardiere, O.); Burke, WJ (Burke, W. J.); Roddy, PA (Roddy, P. A.); Pfaff, RF (Pfaff, R. F., Jr.); Wilson, GR (Wilson, G. R.); Hunton, DE (Hunton, D. E.) |
|
Source: GEOPHYSICAL RESEARCH LETTERS Volume: 36 Article Number: L00C02 DOI: 10.1029/2009GL038946 Published: JUL 22 2009 |
|
Times Cited in Web of Science: 8 |
|
Total Times Cited: 8 |
|
Abstract: Using electric field measurements as inputs, the assimilative physics-based ionospheric model (PBMOD) successfully reproduced density depletions observed at early morning local times during four consecutive orbits of the Communication/Navigation Outage Forecasting System (C/NOFS) satellite on 17 June 2008. However, the PBMOD running with plasma drift data from empirical models as inputs predicted neither plasma depletions nor irregularities on this day. Coincident over flights of a large depletion by C/NOFS and the DMSP-F17 satellite allow estimates of its longitudinal and latitudinal scale sizes. The satellite-based estimates are shown to be in reasonable agreement with PBMOD predictions. The model's reproduction of observed temporal and spatial distributions of plasma depletions suggests that our assimilative technique can be used to enhance space-weather forecasts. Citation: Su, Y.-J., J. M. Retterer, O. de La Beaujardiere, W. J. Burke, P. A. Roddy, R. F. Pfaff Jr., G. R. Wilson, and D. E. Hunton ( 2009), Assimilative modeling of equatorial plasma depletions observed by C/NOFS, Geophys. Res. Lett., 36, L00C02, doi:10.1029/2009GL038946. |
|
Accession Number: WOS:000268349700002 |
|
ISSN: 0094-8276 |
|
Record 4 of 38 |
|
Title: Broad plasma decreases in the equatorial ionosphere |
|
Author(s): Huang, CY (Huang, Cheryl Y.); Marcos, FA (Marcos, Frank A.); Roddy, PA (Roddy, Patrick A.); Hairston, MR (Hairston, Marc R.); Coley, WR (Coley, W. Robin); Roth, C (Roth, Christopher); Bruinsma, S (Bruinsma, Sean); Hunton, DE (Hunton, Donald E.) |
|
Source: GEOPHYSICAL RESEARCH LETTERS Volume: 36 Article Number: L00C04 DOI: 10.1029/2009GL039423 Published: AUG 6 2009 |
|
Times Cited in Web of Science: 13 |
|
Total Times Cited: 13 |
|
Abstract: During June 2008 broad plasma density decreases (BPDs) were detected repeatedly by the Planar Langmuir Probe (PLP) on board the Communication/Navigation Outage Forecasting System (C/NOFS) satellite. These density minima, not to be confused with Equatorial Plasma Bubbles (EPBs), occurred within 15 degrees of the equator, consisted of reductions in plasma density up to an order of magnitude and extended across several degrees in azimuth along the orbit. Analysis revealed that the BPDs occurred nearly daily from May through July 2008 on C/NOFS, and that the widest BPDs were observed in the vicinity of the South Atlantic Anomaly (SAA). Similar BPDs simultaneous with the C/NOFS measurements were observed by instruments on the CHAllenging Minisatellite Payload (CHAMP) and Defense Meteorological Satellite Program (DMSP) satellites. An examination of plasma densities observed by the DMSP satellites over several years revealed that these phenomena were a frequent occurrence during (1) the period around June solstices; during (2) solar minimum years; (3) in the vicinity of the SAA. Neutral densities were examined during periods when BPDs were detected, and at times there are simultaneous neutral depletions. One possible explanation is a decrease in temperature of both ions and neutrals in the equatorial region at these times, consistent with downwelling in the ionosphere and thermosphere. Measurements of plasma temperatures on DMSP support this hypothesis. Citation: Huang, C. Y., F. A. Marcos, P. A. Roddy, M. R. Hairston, W. R. Coley, C. Roth, S. Bruinsma, and D. E. Hunton (2009), Broad plasma decreases in the equatorial ionosphere, Geophys. Res. Lett., 36, L00C04, doi: 10.1029/2009GL039423. |
|
Accession Number: WOS:000268819900008 |
|
ISSN: 0094-8276 |
|
Record 5 of 38 |
|
Title: C/NOFS observations of intermediate and transitional scale-size equatorial spread F irregularities |
|
Author(s): Rodrigues, FS (Rodrigues, F. S.); Kelley, MC (Kelley, M. C.); Roddy, PA (Roddy, P. A.); Hunton, DE (Hunton, D. E.); Pfaff, RF (Pfaff, R. F.); de La Beaujardiere, O (de La Beaujardiere, O.); Bust, GS (Bust, G. S.) |
|
Source: GEOPHYSICAL RESEARCH LETTERS Volume: 36 Article Number: L00C05 DOI: 10.1029/2009GL038905 Published: AUG 6 2009 |
|
Times Cited in Web of Science: 2 |
|
Total Times Cited: 2 |
|
Abstract: We present initial results of the analysis of high sampling rate (512 Hz) measurements made by the Planar Langmuir Probe (PLP) instrument and the Vector Electric Field Instrument (VEFI) onboard the Communication/Navigation Outage Forecasting System (C/NOFS) satellite. This letter focuses on the analysis of irregularities with scale-sizes in the intermediate (0.1-10 km) and transitional (10100 m) domains observed when the satellite was flying through a large equatorial spread F (ESF) depletion on the night of October 9-10, 2008 over South America. The results presented in this letter suggest the operation of a diffusive subrange in the density power spectra and the possibility of an inertial plasma regime being observed at relatively low altitudes as a result of the long-lasting solar minimum conditions. Citation: Rodrigues, F. S., M. C. Kelley, P. A. Roddy, D. E. Hunton, R. F. Pfaff, O. de La Beaujardiere, and G. S. Bust (2009), C/NOFS observations of intermediate and transitional scale-size equatorial spread F irregularities, Geophys. Res. Lett., 36, L00C05, doi: 10.1029/2009GL038905. |
|
Accession Number: WOS:000268819900005 |
|
ISSN: 0094-8276 |
|
Record 6 of 38 |
|
Title: C/NOFS observations of deep plasma depletions at dawn |
|
Author(s): de La Beaujardiere, O (de La Beaujardiere, Odile); Retterer, JM (Retterer, John M.); Pfaff, RF (Pfaff, Robert F.); Roddy, PA (Roddy, Patrick A.); Roth, C (Roth, Christopher); Burke, WJ (Burke, William J.); Su, YJ (Su, Yi Jiun); Kelley, MC (Kelley, Michael C.); Ilma, RR (Ilma, Ronald R.); Wilson, GR (Wilson, Gordon R.); Gentile, LC (Gentile, Louise C.); Hunton, DE (Hunton, Donald E.); Cooke, DL (Cooke, David L.) |
|
Source: GEOPHYSICAL RESEARCH LETTERS Volume: 36 Article Number: L00C06 DOI: 10.1029/2009GL038884 Published: AUG 7 2009 |
|
Times Cited in Web of Science: 22 |
|
Total Times Cited: 22 |
|
Abstract: The Communication/Navigation Outage Forecasting System (C/NOFS) satellite was launched in 2008, during solar minimum conditions. An unexpected feature in the C/NOFS plasma density data is the presence of deep plasma depletions observed at sunrise at all satellite altitudes. Ionospheric irregularities are often embedded within these dawn depletions. Their frequencies strongly depend on longitude and season. Dawn depletions are also observed in coincident satellite passes such as DMSP and CHAMP. In one example the depletion extended 50 degrees x 14 degrees in the N-S and E-W directions, respectively. These depletions are caused by upward plasma drifts observed in C/NOFS and ground-based measurements. The reason for these upward drifts is still unresolved. We discuss the roles of dynamo electric fields, over-shielding, and tidal effects as sources for the reported depletions. Citation: de La Beaujardiere, O., et al. (2009), C/NOFS observations of deep plasma depletions at dawn, Geophys. Res. Lett., 36, L00C06, doi: 10.1029/2009GL038884. |
|
Accession Number: WOS:000268820000005 |
|
ISSN: 0094-8276 |
|
Record 7 of 38 |
|
Title: C/NOFS and radar observations during a convective ionospheric storm event over South America |
|
Author(s): Kelley, MC (Kelley, M. C.); Rodrigues, FS (Rodrigues, F. S.); Makela, JJ (Makela, J. J.); Tsunoda, R (Tsunoda, R.); Roddy, PA (Roddy, P. A.); Hunton, DE (Hunton, D. E.); Retterer, JM (Retterer, J. M.); de La Beaujardiere, O (de La Beaujardiere, O.); de Paula, ER (de Paula, E. R.); Ilma, RR (Ilma, R. R.) |
|
Source: GEOPHYSICAL RESEARCH LETTERS Volume: 36 Article Number: L00C07 DOI: 10.1029/2009GL039378 Published: AUG 21 2009 |
|
Times Cited in Web of Science: 4 |
|
Total Times Cited: 4 |
|
Abstract: The development of a convective ionospheric storm is studied using three radars, the C/NOFS satellite, airglow instrumentation, and a numerical model. First detected in the form of convective plumes over the Eastern Pacific, plasma irregularities, airglow signatures, plumes, and irregularities were also detected over Brazil and then Peru. Dynamo conditions were such that a modest prereversal enhancement was recorded at both Christmas Island and Peru and probably over Brazil as well. No prereversal enhancement occurred during the next two days and no plumes were detected. The numerical model reproduced the results quite well over Peru. Evidence for seeding by both gravity waves and the Kelvin-Helmholtz instability is presented. Citation: Kelley, M. C., F. S. Rodrigues, J. J. Makela, R. Tsunoda, P. A. Roddy, D. E. Hunton, J. M. Retterer, O. de La Beaujardiere, E. R. de Paula, and R. R. Ilma (2009), C/NOFS and radar observations during a convective ionospheric storm event over South America, Geophys. Res. Lett., 36, L00C07, doi: 10.1029/2009GL039378. |
|
Accession Number: WOS:000269244100004 |
|
ISSN: 0094-8276 |
|
Record 8 of 38 |
|
Title: Comparisons of equatorial irregularities measurements from C/NOFS: TEC using CERTO and CITRIS with in-situ plasma density |
|
Author(s): Siefring, CL (Siefring, Carl L.); Bernhardt, PA (Bernhardt, Paul A.); Roddy, PA (Roddy, Patrick A.); Hunton, DE (Hunton, Donald E.) |
|
Source: GEOPHYSICAL RESEARCH LETTERS Volume: 36 Article Number: L00C08 DOI: 10.1029/2009GL038985 Published: SEP 9 2009 |
|
Times Cited in Web of Science: 5 |
|
Total Times Cited: 5 |
|
Abstract: Equatorial plasma density measurements using two techniques are analyzed. The unique instrument complement on C/NOFS (Communication/Navigations Outages Forecasting System) allows for the measurement of TEC (Total Electron Content) using the CERTO (Coherent Electromagnetic Radio TOmography) beacon and measurement of in-situ densities using the PLP (Planar Langmuir Probe). In a nearby orbit, the CITRIS (sCIntilation and TEC Receiver In Space) was available for complementary measurements. TEC was measured with 1) CERTO-CITRIS conjunctions that allow estimates of absolute TEC and 2) CITRIS with ground-based DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) beacons. The combination of the remote and in-situ techniques provides more information, enhanced believability for probe measurements as the satellite transitions from darkness to sunlight, as well as cross-calibration and better accuracy for both data sets. The measurements presented are taken in unusually quiet geomagnetic conditions and indicate equatorial irregularities are present nearly 80% of the time for nighttime measurements. Citation: Siefring, C. L., P. A. Bernhardt, P. A. Roddy, and D. E. Hunton (2009), Comparisons of equatorial irregularities measurements from C/NOFS: TEC using CERTOand CITRISwith in-situ plasma density, Geophys. Res. Lett., 36, L00C08, doi: 10.1029/2009GL038985. |
|
Accession Number: WOS:000269756000002 |
|
ISSN: 0094-8276 |
|
Record 9 of 38 |
|
Title: C/NOFS observations of plasma density and electric field irregularities at post-midnight local times |
|
Author(s): Burke, WJ (Burke, W. J.); de la Beaujardiere, O (de la Beaujardiere, O.); Gentile, LC (Gentile, L. C.); Hunton, DE (Hunton, D. E.); Pfaff, RF (Pfaff, R. F.); Roddy, PA (Roddy, P. A.); Su, YJ (Su, Y. -J.); Wilson, GR (Wilson, G. R.) |
|
Source: GEOPHYSICAL RESEARCH LETTERS Volume: 36 Article Number: L00C09 DOI: 10.1029/2009GL038879 Published: SEP 19 2009 |
|
Times Cited in Web of Science: 13 |
|
Total Times Cited: 13 |
|
Abstract: We report on plasma densities and electric fields measured by the C/NOFS satellite between 10 and 20 June 2008. Midway through the interval, geomagnetic conditions changed from quiescent to disturbed as a high speed stream (HSS) in the solar wind passed Earth. During the HSS passage C/NOFS encountered post-midnight irregularities that ranged from strong equatorial plasma bubbles to longitudinally broad depletions. At the leading edge of the HSS the interplanetary magnetic field rapidly intensified and rotated causing auroral electrojet currents to rise and fall within a few hours. As the electrojet relaxed, C/NOFS witnessed a rapid transition from a weakly to a strongly disturbed equatorial ionosphere that lasted similar to 10 hours. Eastward polarization electric fields intensified within locally depleted flux tubes. We discuss relative contributions of gravity-driven currents, overshielding electric fields and disturbance dynamos as drivers of post-midnight depletions. Citation: Burke, W.J., O. de La Beaujardiere, L. C. Gentile, D. E. Hunton, R. F. Pfaff, P. A. Roddy, Y.- J. Su, and G. R. Wilson (2009), C/NOFS observations of plasma density and electric field irregularities at post-midnight local times, Geophys. Res. Lett., 36, L00C09, doi: 10.1029/2009GL038879. |
|
Accession Number: WOS:000270055300001 |
|
ISSN: 0094-8276 |
|
Record 10 of 38 |
|
Title: Modeling the climatology of equatorial plasma bubbles observed by DMSP |
|
Author(s): Retterer, JM (Retterer, J. M.); Gentile, LC (Gentile, L. C.) |
|
Source: RADIO SCIENCE Volume: 44 Article Number: RS0A31 DOI: 10.1029/2008RS004057 Published: SEP 25 2009 |
|
Times Cited in Web of Science: 6 |
|
Total Times Cited: 6 |
|
Abstract: Space environmental sensors on polar-orbiting Defense Meteorological Satellite Program (DMSP) spacecraft occasionally encounter plasma density depletions when they cross the geomagnetic equator in the evening sector. These equatorial plasma bubbles (EPBs) are observed around the times and locations when equatorial spread F and radio scintillation phenomena tend to occur. The solar cycle, seasonal, and longitudinal variations in the observed frequency of these depletions (determined over the past 19 years) are indeed similar to those of scintillation. To test our understanding of EPB formation, we simulated the observations using PBMOD, a suite of first-principle models of the ambient ionosphere and EPB formation, driven by climatological models for its input parameters such as the plasma drift velocity. Maps of the model calculations of EPB frequencies at 840 km as functions of season and longitude exhibit patterns similar to the DMSP observations, including the expected peaks in EPB frequency near the equinoxes, an additional winter peak in the American sector, a summer peak in the Pacific sector, and the proper trends with solar cycle phase. Adjusting the model to reproduce the DMSP EPB occurrence frequencies in detail will allow us to fine tune PBMOD and provides a means for using the DMSP data to enhance the empirical drivers for the Communication/Navigation Outage Forecasting System (C/NOFS) mission. |
|
Accession Number: WOS:000270238300001 |
|
ISSN: 0048-6604 |
|
Record 11 of 38 |
|
Title: First observations of large-scale wave structure and equatorial spread F using CERTO radio beacon on the C/NOFS satellite |
|
Author(s): Thampi, SV (Thampi, Smitha V.); Yamamoto, M (Yamamoto, Mamoru); Tsunoda, RT (Tsunoda, Roland T.); Otsuka, Y (Otsuka, Yuichi); Tsugawa, T (Tsugawa, Takuya); Uemoto, J (Uemoto, Jyunpei); Ishii, M (Ishii, Mamoru) |
|
Source: GEOPHYSICAL RESEARCH LETTERS Volume: 36 Article Number: L18111 DOI: 10.1029/2009GL039887 Published: SEP 26 2009 |
|
Times Cited in Web of Science: 8 |
|
Total Times Cited: 8 |
|
Abstract: First observations of large-scale wave structure (LSWS) and the subsequent development of equatorial spread F (ESF), using total electron content (TEC) derived from the ground based reception of beacon signals from the CERTO (Coherent Electromagnetic Radio Tomography) radio beacon on board C/NOFS (Communications/Navigation Outage Forecasting System) satellite, are presented. Selected examples of TEC variations, using measurements made during January 2009 from Bac Lieu, Vietnam (9.2 degrees N, 105.6 degrees E geographic, 1.7 degrees N magnetic dip latitude) are presented to illustrate two key findings: (1) LSWS appears to play a more important role in the development of ESF than the post-sunset rise (PSSR) of the F-layer, and (2) LSWS can appear well before E region sunset. Other findings, that LSWS does not have significant zonal drift in the initial stages of growth, and can have zonal wavelengths of several hundred kilometers, corroborate earlier reports. Citation: Thampi, S. V., M. Yamamoto, R. T. Tsunoda, Y. Otsuka, T. Tsugawa, J. Uemoto, and M. Ishii (2009), First observations of large-scale wave structure and equatorial spread F using CERTO radio beacon on the C/NOFS satellite, Geophys. Res. Lett., 36, L18111, doi: 10.1029/2009GL039887. |
|
Accession Number: WOS:000270235400005 |
|
ISSN: 0094-8276 |
|
Record 12 of 38 |
|
Title: Ion temperature and density relationships measured by CINDI from the C/NOFS spacecraft during solar minimum |
|
Author(s): Coley, WR (Coley, W. R.); Heelis, RA (Heelis, R. A.); Hairston, MR (Hairston, M. R.); Earle, GD (Earle, G. D.); Perdue, MD (Perdue, M. D.); Power, RA (Power, R. A.); Harmon, LL (Harmon, L. L.); Holt, BJ (Holt, B. J.); Lippincott, CR (Lippincott, C. R.) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 115 Article Number: A02313 DOI: 10.1029/2009JA014665 Published: FEB 26 2010 |
|
Times Cited in Web of Science: 8 |
|
Total Times Cited: 8 |
|
Abstract: The Ion Velocity Meter (IVM), a part of the CINDI instrument package on board the C/NOFS spacecraft, makes in situ measurements of plasma temperature, composition, density, and velocity. The 16 April 2008 launch of C/NOFS coincided with the deepest solar minimum since the space age began with F(10.7) cm radio fluxes in the 60-70 solar flux unit range. Because of the 13 degrees inclination of the orbit the location of the perigee advances through all local times in about 66 days. This allows seasonal sampling of ionospheric temperature, density, and composition as a function of local time, magnetic latitude, and altitude. Measurements taken near the spacecraft's 402 km perigee altitude indicate an unusually cold low-density ionosphere with nighttime ion temperatures at the magnetic equator reaching as low as 600 K with an [O(+)]/[H(+)] ratio of 4 and maximum daytime temperatures of 1300 K. The O(+) to H(+) transition height is very low and at the highest altitudes measured H(+) comprises over 75% of the ionospheric plasma at all local times. We compare average values of the measured parameters with those from the International Reference Ionosphere and with incoherent scatter radar measurements from Jicamarca. |
|
Accession Number: WOS:000275037400006 |
|
ISSN: 0148-0227 |
|
Record 13 of 38 |
|
Title: Correlation of in situ measurements of plasma irregularities with ground-based scintillation observations |
|
Author(s): Roddy, PA (Roddy, P. A.); Hunton, DE (Hunton, D. E.); Ballenthin, JO (Ballenthin, J. O.); Groves, KM (Groves, K. M.) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 115 Article Number: A06303 DOI: 10.1029/2010JA015288 Published: JUN 15 2010 |
|
Times Cited in Web of Science: 2 |
|
Total Times Cited: 2 |
|
Abstract: We present here the first comparison of in situ ion density fluctuations measured by the Planar Langmuir Probe on Communication\Navigation Outage Forecasting System (C/NOFS) with coincident ground-based measurements of scintillation from the Scintillation Decision Aid (SCINDA) network and coherent scatter radar located on Christmas Island (3 degrees N, 157 degrees W) over a 15 month period from May 2008 through June 2009. The Planar Langmuir Probe on C/NOFS measures absolute ion densities from 10 to 10(8) cm(-3) at a rate up to 1024 Hz. The instrument is conceptually similar to ion traps and retarding potential analyzers that have flown on many past satellite and rocket missions. However, the present design includes advances in electronic capability compared with past designs. Initial results from this study show that in situ density fluctuations observed on magnetic flux tubes that pass over Christmas Island can be used as an indicator of ionospheric radio wave scintillation at that site. This is true even when the measurements are made at horizontal ranges of over 1000 km away from the ground site as long as the field line apex altitudes are less than similar to 600 km. |
|
Accession Number: WOS:000278991700003 |
|
ISSN: 0148-0227 |
|
Record 14 of 38 |
|
Title: Zonal drift of plasma particles inside equatorial plasma bubbles and its relation to the zonal drift of the bubble structure |
|
Author(s): Huang, CS (Huang, Chao-Song); de La Beaujardiere, O (de La Beaujardiere, O.); Pfaff, RF (Pfaff, R. F.); Retterer, JM (Retterer, J. M.); Roddy, PA (Roddy, P. A.); Hunton, DE (Hunton, D. E.); Su, YJ (Su, Y. -J.); Su, SY (Su, S. -Y.); Rich, FJ (Rich, F. J.) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 115 Article Number: A07316 DOI: 10.1029/2010JA015324 Published: JUL 17 2010 |
|
Times Cited in Web of Science: 6 |
|
Total Times Cited: 6 |
|
Abstract: It has been observed that the zonal drift velocity of equatorial plasma bubbles is generally eastward. However, it has not been well understood whether the zonal drift of plasma bubbles is the same as the ambient plasma drift and what process causes differences in the drift velocities of the ambient plasma and bubbles. In this study we analyze the ion drift velocities measured by the Defense Meteorological Satellites Program and ROCSAT-1 satellites and the electric fields measured by the Communications/Navigation Outage Forecasting System (C/NOFS) satellite in the presence of equatorial spread F. We find that the zonal drift velocity of the plasma particles inside plasma bubbles is significantly different from the ambient plasma drift. The relative zonal velocity of the ions inside the depletion region with respect to the ambient plasma is generally westward. In most cases it can be as high as several hundreds of meters per second. The plasma bubbles detected by the C/NOFS satellite in the midnight-dawn sector are still growing, and the polarization electric field inside the postmidnight bubbles is much stronger than the electric field in the ambient plasma. We suggest that the zonal drift velocity of the plasma particles inside the depletion region is driven by polarization electric field. When a plasma bubble is tilted, the E x B drift velocity caused by the polarization electric field has an upward component and a zonal component. Because of the zonal motion of the plasma particles inside the bubble, the eastward drift velocity of the bubble structure is faster than the ambient plasma drift for a west-tilted bubble and slower than the ambient plasma drift for an east-tilted bubble. |
|
Accession Number: WOS:000280051400007 |
|
ISSN: 0148-0227 |
|
Record 15 of 38 |
|
Title: V/UHF space radars: Spatial phase decorrelation of transionospheric signals in the equatorial region |
|
Author(s): van de Kamp, MMJL (van de Kamp, Max M. J. L.); Cannon, PS (Cannon, Paul S.); Watson, RJ (Watson, Robert J.) |
|
Source: RADIO SCIENCE Volume: 45 Article Number: RS4012 DOI: 10.1029/2009RS004226 Published: AUG 24 2010 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: The spatial decorrelation of V/UHF signals by equatorial ionospheric turbulence is studied using 150 and 400 MHz signals transmitted from low-earth-orbiting beacon satellites. The signals are monitored on a linear array of spaced antennas located on Ascension Island, and processed coherently to determine the cross-correlations of the phases of the received signals. Analyzing signals from the low-inclination satellite C/NOFS has provided an opportunity to investigate the correlation variations in and out of scintillating structures. As a necessary step, the geometrical component of the phase difference between antennas has been accurately removed by adjusting the satellite orbital information using the measured phases. In order to unambiguously measure the spatial phase correlation without any temporal effects, the phase cross-correlation was calculated as the cross-correlation function of time-synchronized signals. As expected, the VHF signals were more affected by scintillation than the UHF signals. When the signal propagated through patches of strong scintillation, the VHF signal became completely uncorrelated over an ionospheric distance of 130 m, while over the same distance the UHF phase correlation decreased to 0.55. The time-synchronized technique limited the spatial variations assessed to east-west distances of similar to 300 m. To extend this range, a novel 'phase reconstruction' technique was developed to link arrays of samples together. In the absence of scintillation the measured decorrelation distance is similar to 10 km at both frequencies, but with increasing scintillation, the decorrelation distance falls to similar to 100 m at VHF and 300 m at UHF. A clear relation between the decorrelation distance of the measured phase and S(4) is observed and a simple empirical model has been derived. |
|
Accession Number: WOS:000281418000001 |
|
ISSN: 0048-6604 |
|
Record 16 of 38 |
|
Title: Mapping the duskside topside ionosphere with CINDI and DMSP |
|
Author(s): Hairston, MR (Hairston, Marc R.); Coley, WR (Coley, William R.); Heelis, RA (Heelis, R. A.) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 115 Article Number: A08324 DOI: 10.1029/2009JA015051 Published: AUG 28 2010 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: The CINDI plasma instrument package on board the C/NOFS spacecraft performs in situ measurements of the velocity, temperature, composition, and density of ionospheric ions. In a 402 by 849 km orbit with a 13 inclination its apogee reaches the topside ionosphere at the same altitude as the polar-orbiting DMSP spacecraft that also carry similar plasma measurement packages. Over the course of about 66 days the apogee of C/NOFS' orbit cycles once through all solar local times. This paper presents the apogee observations from the CINDI instruments between 21 August and 5 September 2008 when the C/NOFS' apogee passed through the orbital planes of the duskside equatorial crossings of the four operational DMSP spacecraft. Combining the data from all five spacecraft reveals the spatial distribution of the total ion density, the ion temperature, and the ion composition at these altitudes. Comparisons of these observed distributions from CINDI and DMSP are used to check the agreement between the new CINDI instruments and the long-operating DMSP instruments. The results of the density and temperature measurements show good agreement, however there are two regions where the composition and temperature measurements show discrepancies that result from the limitation of the plasma instruments in an environment of extremely low density plasma composed of over 85% light ions (H(+) and He(+)). |
|
Accession Number: WOS:000281417700003 |
|
ISSN: 0148-0227 |
|
Record 17 of 38 |
|
Title: Low-latitude measurements of neutral thermospheric helium dominance near 400 km during extreme solar minimum |
|
Author(s): Haaser, RA (Haaser, R. A.); Earle, GD (Earle, G. D.); Heelis, RA (Heelis, R. A.); Coley, WR (Coley, W. R.); Klenzing, JH (Klenzing, J. H.) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 115 Article Number: A11318 DOI: 10.1029/2010JA015325 Published: NOV 19 2010 |
|
Times Cited in Web of Science: 1 |
|
Total Times Cited: 1 |
|
Abstract: Since the middle of 2008 solar activity has been unusually low, resulting in unusual atmospheric conditions, including significant changes in the pressure and neutral constituents at altitudes near 400 km at low latitudes. These attributes have been measured by the Coupled Ion-Neutral Dynamics Investigation instruments aboard the Communication/Navigation Outage Forecast System (C/NOFS) satellite. The cross-track sensor aboard C/NOFS is designed to measure the neutral pressure in an atmosphere with pressures larger than 10 (8) Torr, from which the atmospheric scale height can be estimated. In the contracted thermosphere during the current solar minimum (analyzed from June 2008 to August 2009), the instrument data indicate a dominance of neutral helium near the satellite perigee (400 km). This conclusion is found to be consistent with the measured mean drag on the satellite, thus validating the basic functionality of the cross-track sensor. |
|
Accession Number: WOS:000284488000002 |
|
ISSN: 0148-0227 |
|
Record 18 of 38 |
|
Title: Observations of DC electric fields in the low-latitude ionosphere and their variations with local time, longitude, and plasma density during extreme solar minimum |
|
Author(s): Pfaff, R (Pfaff, R.); Rowland, D (Rowland, D.); Freudenreich, H (Freudenreich, H.); Bromund, K (Bromund, K.); Le, G (Le, G.); Acuna, M (Acuna, M.); Klenzing, J (Klenzing, J.); Liebrecht, C (Liebrecht, C.); Martin, S (Martin, S.); Burke, WJ (Burke, W. J.); Maynard, NC (Maynard, N. C.); Hunton, DE (Hunton, D. E.); Roddy, PA (Roddy, P. A.); Ballenthin, JO (Ballenthin, J. O.); Wilson, GR (Wilson, G. R.) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 115 Article Number: A12324 DOI: 10.1029/2010JA016023 Published: DEC 21 2010 |
|
Times Cited in Web of Science: 12 |
|
Total Times Cited: 12 |
|
Abstract: DC electric fields and associated E x B plasma drifts detected with the double-probe experiment on the C/NOFS satellite during extreme solar minimum conditions near the June 2008 solstice are shown to be highly variable, with weak to moderate ambient amplitudes of similar to 1-2 mV/m (similar to 25-50 m/s). Average field or drift patterns show similarities to those reported for more active solar conditions, i.e., eastward and outward during day and westward and inward at night. However, these patterns vary significantly with longitude and are not always present. Daytime vertical drifts near the magnetic equator are largest in the prenoon sector. Observations of weak to nonexistent prereversal enhancements in the vertical drifts near sunset are attributable to reduced dynamo activity during solar minimum as well as seasonal effects. Enhanced meridional drifts are observed near sunrise in certain longitude regions, precisely where the enhanced eastward flow that persisted from earlier local times terminates. The nightside ionosphere is characterized by larger-amplitude, structured electric fields dominated by horizontal scales of 500-1500 km even where local plasma densities appear relatively undisturbed. Data acquired during successive orbits indicate that plasma drifts and densities are persistently organized by longitude. The high duty cycle of the C/NOFS observations and its unique orbit promise to expose new physics of the low-latitude ionosphere. |
|
Accession Number: WOS:000285639300016 |
|
ISSN: 0148-0227 |
|
Record 19 of 38 |
|
Title: Study of oblique whistlers in the low-latitude ionosphere, jointly with the C/NOFS satellite and the World-Wide Lightning Location Network |
|
Author(s): Jacobson, AR (Jacobson, A. R.); Holzworth, RH (Holzworth, R. H.); Pfaff, RF (Pfaff, R. F.); McCarthy, MP (McCarthy, M. P.) |
|
Source: ANNALES GEOPHYSICAE Volume: 29 Issue: 5 Pages: 851-863 DOI: 10.5194/angeo-29-851-2011 Published: 2011 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: We use the C/NOFS satellite's Vector Electric Field Instrument (VEFI) to study the relationship of impulsive electron whistlers in the low-latitude ionosphere to lightning strokes located by the World-Wide Lightning Location Network (WWLLN). In order to systematize this work, we develop an automated algorithm for recognizing and selecting the signatures of electron whistlers amongst many Very Low Frequency (VLF) recordings provided by VEFI. We demonstrate the application of this whistler-detection algorithm to data mining of a similar to two-year archive of VEFI recordings. It is shown that the relatively simple oblique electron whistler adequately accounts of the great majority of low-latitude oscillatory VLF waves seen in this study. |
|
Accession Number: WOS:000291092600013 |
|
ISSN: 0992-7689 |
|
Record 20 of 38 |
|
Title: Evolution of equatorial ionospheric plasma bubbles and formation of broad plasma depletions measured by the C/NOFS satellite during deep solar minimum |
|
Author(s): Huang, CS (Huang, Chao-Song); de la Beaujardiere, O (de la Beaujardiere, O.); Roddy, PA (Roddy, P. A.); Hunton, DE (Hunton, D. E.); Pfaff, RF (Pfaff, R. F.); Valladares, CE (Valladares, C. E.); Ballenthin, JO (Ballenthin, J. O.) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 116 Article Number: A03309 DOI: 10.1029/2010JA015982 Published: MAR 8 2011 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: An unexpected feature revealed by the measurements of the Communication/Navigation Outage Forecasting System (C/NOFS) satellite is the presence of broad plasma depletions in the midnight-dawn sector during deep solar minimum. It has not been well understood what causes the broad plasma depletions and how equatorial plasma bubbles are related to the broad depletions. In this paper we present the C/NOFS measurements of equatorial plasma bubbles and broad depletions in a few cases. The ion density perturbations and enhanced ion vertical velocity are first identified in the topside F region at similar to 2200 LT, suggesting that the plasma bubbles start to form earlier at lower altitudes. The observations show that the plasma bubbles observed in the midnight-dawn sector may originate in the evening sector. The plasma bubbles continue growing for more than 3.3 h, and the decay time of the bubbles is also longer than 3.3 h. The continuous growth of the plasma bubbles in the evening sector and the slow decay after midnight determine that most plasma bubbles become fully developed and are easily detected in the midnight-dawn sector. The plasma flow inside the bubbles remains strongly upward throughout the entire nighttime. We propose the following mechanism for the generation of wide plasma bubbles and broad depletions. A series of plasma bubbles is generated through the Rayleigh-Taylor instability process over a large longitudinal range. These plasma bubbles grow and merge to form a wide bubble (width of similar to 700 km as observed), and multiple regular and/or wide bubbles can further merge to form broad plasma depletions (thousands of kilometers in longitude). The ion vertical drift inside each plasma bubble is driven by the polarization electric field and remains large after the bubbles have merged. This mechanism provides a reasonable interpretation of the large upward ion drift velocity inside the broad depletion region. |
|
Accession Number: WOS:000288330900002 |
|
ISSN: 0148-0227 |
|
Record 21 of 38 |
|
Title: Climatology of plasma density depletions observed by DMSP in the dawn sector |
|
Author(s): Gentile, LC (Gentile, L. C.); Burke, WJ (Burke, W. J.); Roddy, PA (Roddy, P. A.); Retterer, JM (Retterer, J. M.); Tsunoda, RT (Tsunoda, R. T.) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 116 Article Number: A03321 DOI: 10.1029/2010JA016176 Published: MAR 19 2011 |
|
Times Cited in Web of Science: 1 |
|
Total Times Cited: 1 |
|
Abstract: Prior to the launch of the Communication/Navigation Outage Forecasting System (C/NOFS) satellite, equatorial plasma bubbles (EPBs) were regarded as postsunset phenomena. However, during this recent solar minimum the planar Langmuir probe (PLP) on the C/NOFS satellite has detected very few EPBs after sunset; most plasma density depletions have been observed between local midnight and dawn. We take advantage of the long history of plasma density measurements by a similar sensor on Defense Meteorological Satellite Program (DMSP) spacecraft to determine whether this change is typical of solar minima in general or unique to the present extended quiet time. In 2008 and 2009 the DMSP occurrence rates of topside plasma depletions in the dawn sector were unexpectedly high around the June and December solstices and extremely low near the March and September equinoxes. Dawn sector measurements from solar minimum years 1996-1997 exhibit similar seasonal and longitudinal distributions, but occurrence rates are significantly lower. While our analysis suggests that prevailing low levels of solar EUV flux and driving electric fields establish conditions favorable for the growth of postmidnight depletions, the primary causes of observed seasonal-longitudinal distributions remain unresolved. |
|
Accession Number: WOS:000288606500001 |
|
ISSN: 0148-0227 |
|
Record 22 of 38 |
|
Title: Equatorial scintillation calculations based on coherent scatter radar and C/NOFS data |
|
Author(s): Costa, E (Costa, Emanoel); de Paula, ER (de Paula, Eurico R.); Rezende, LFC (Rezende, L. F. C.); Groves, KM (Groves, Keith M.); Roddy, PA (Roddy, Patrick A.); Dao, EV (Dao, Eugene V.); Kelley, MC (Kelley, Michael C.) |
|
Source: RADIO SCIENCE Volume: 46 Article Number: RS2011 DOI: 10.1029/2010RS004435 Published: APR 7 2011 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: During its transit through a region of equatorial ionospheric irregularities, sensors on board the Communication/Navigation Outage Forecasting System (C/NOFS) satellite provide a one-dimensional description of the medium, which can be extended to two dimensions if the structures are assumed to be elongated in the direction of the magnetic field lines. The C/NOFS scintillation calculation approach assumes that the medium is equivalent to a diffracting screen with random phase fluctuations that are proportional to the irregularities in the total electron content, specified through the product of the directly measured electron density by an estimated extent of the irregularity layer along the raypaths. Within the international collaborative effort anticipated by the C/NOFS Science Definition Team, the present work takes the vertical structure of the irregularities into more detailed consideration, which could lead to improved predictions of scintillation. Initially, it describes a flexible model for the power spectral density of the equatorial ionospheric irregularities, estimates its shape parameters from C/NOFS in situ data and uses the signal-to-noise ratio S/N measurements by the Sao Luis coherent scatter radar to estimate the mean square electron density fluctuation <Delta N(2)> within the corresponding sampled volume. Next, it presents an algorithm for the wave propagation through a three-dimensional irregularity layer which considers the variations of <Delta N(2)> along the propagation paths according to observations by the radar. Data corresponding to several range-time-intensity maps from the radar is used to predict time variations of the scintillation index S(4) at the L1 Global Positioning System (GPS) frequency (1575.42 MHz). The results from the scintillation calculations are compared with corresponding measurements by the colocated Sao Luis GPS scintillation monitor for an assessment of the prediction capability of the present formulation. |
|
Accession Number: WOS:000289360200001 |
|
ISSN: 0048-6604 |
|
Record 23 of 38 |
|
Title: Longitudinal and seasonal dependence of nighttime equatorial plasma density irregularities during solar minimum detected on the C/NOFS satellite |
|
Author(s): Dao, E (Dao, E.); Kelley, MC (Kelley, M. C.); Roddy, P (Roddy, P.); Retterer, J (Retterer, J.); Ballenthin, JO (Ballenthin, J. O.); de La Beaujardiere, O (de La Beaujardiere, O.); Su, YJ (Su, Y. -J.) |
|
Source: GEOPHYSICAL RESEARCH LETTERS Volume: 38 Article Number: L10104 DOI: 10.1029/2011GL047046 Published: MAY 21 2011 |
|
Times Cited in Web of Science: 1 |
|
Total Times Cited: 1 |
|
Abstract: During the night in the F region about the equator, plasma density depletions form, causing scintillation. In April 2008, the Communications/Navigation Outage Forecasting System (C/NOFS) satellite developed by the Air Force Research Laboratory was launched to predict ionospheric scintillation. Using its Planar Langmuir Probe (PLP), C/NOFS is capable of measuring in situ ion density within the F region over the equator. Plasma irregularities are found regularly during the night. We examine how these irregularities depend on longitude, latitude, and season. The most significant observations from this study are longitudinal structures in which these irregularities most frequently occur. Since similar structure has been found in diurnal tides, we conclude that lower atmospheric tides may play a strong role in determining the amplitude of equatorial irregularities, at least during low solar minimum conditions when the presented observations were made. We propose that this link is likely related to the generation of zonal electric fields by the E-region dynamo. Citation: Dao, E., M. C. Kelley, P. Roddy, J. Retterer, J. O. Ballenthin, O. de La Beaujardiere, and Y.-J. Su (2011), Longitudinal and seasonal dependence of nighttime equatorial plasma density irregularities during solar minimum detected on the C/NOFS satellite, Geophys. Res. Lett., 38, L10104, doi:10.1029/2011GL047046. |
|
Accession Number: WOS:000290872600001 |
|
ISSN: 0094-8276 |
|
Record 24 of 38 |
|
Title: Lightning-generated whistler waves observed by probes on the Communication/Navigation Outage Forecast System satellite at low latitudes |
|
Author(s): Holzworth, RH (Holzworth, R. H.); McCarthy, MP (McCarthy, M. P.); Pfaff, RF (Pfaff, R. F.); Jacobson, AR (Jacobson, A. R.); Willcockson, WL (Willcockson, W. L.); Rowland, DE (Rowland, D. E.) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 116 Article Number: A06306 DOI: 10.1029/2010JA016198 Published: JUN 8 2011 |
|
Times Cited in Web of Science: 2 |
|
Total Times Cited: 2 |
|
Abstract: Direct evidence is presented for a causal relationship between lightning and strong electric field transients inside equatorial ionospheric density depletions. In fact, these whistler mode plasma waves may be the dominant electric field signal within such depletions. Optical lightning data from the Communication/Navigation Outage Forecast System (C/NOFS) satellite and global lightning location information from the World Wide Lightning Location Network are presented as independent verification that these electric field transients are caused by lightning. The electric field instrument on C/NOFS routinely measures lightning-related electric field wave packets or sferics, associated with simultaneous measurements of optical flashes at all altitudes encountered by the satellite (401-867 km). Lightning-generated whistler waves have abundant access to the topside ionosphere, even close to the magnetic equator. |
|
Accession Number: WOS:000291557900002 |
|
ISSN: 0148-0227 |
|
Record 25 of 38 |
|
Title: CONVECTIVE IONOSPHERIC STORMS: A REVIEW |
|
Author(s): Kelley, MC (Kelley, Michael C.); Makela, JJ (Makela, Jonathan J.); de La Beaujardiere, O (de La Beaujardiere, Odile); Retterer, J (Retterer, John) |
|
Source: REVIEWS OF GEOPHYSICS Volume: 49 Article Number: RG2003 DOI: 10.1029/2010RG000340 Published: JUN 22 2011 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: Equatorial spread F (ESF) was discovered almost a century ago using the first radio wave instrument designed to study the upper atmosphere: the ionosonde. The name came from the appearance of reflections from the normally smooth ionosphere, which were spread over the altitude frequency coordinates used by the instrument. Attempts to understand this phenomenon in any depth activated such tools as radars and in situ probes such as rockets and satellites in the 1960s. Over the next 15 years, these tools expanded our experimental understanding enormously, and new nonlinear theoretical methods developed in the late 1970s, which led to proposing a name revision from ESF to convective ionospheric storms. Interest in these phenomena continues, but a new, practical aspect has developed from the associated turbulence effects on communications (transionosphere) and navigation (GPS). The first satellite to specifically investigate this problem and the associated goal of predicting occurrences is under the umbrella of the Communications/Navigation Outage Forecast System (C/NOFS). In contemplating the successful first years of the C/NOFS program, reviewing the state of the art in our knowledge of convective ionospheric storms seems appropriate. We also present some initial results of this satellite program. A major goal of the National Space Weather Program, and of C/NOFS, is predicting these storms, analogous to thunderstorms in the lower atmosphere due to their adverse effects on communication and navigation signals. Although ambitious, predictive capability is a noble and important goal in the current technological age and is potentially within our reach during the coming decade. |
|
Accession Number: WOS:000292152000001 |
|
ISSN: 8755-1209 |
|
Record 26 of 38 |
|
Title: Multiple phase screen modeling of ionospheric scintillation along radio occultation raypaths |
|
Author(s): Carrano, CS (Carrano, Charles S.); Groves, KM (Groves, Keith M.); Caton, RG (Caton, Ronald G.); Rino, CL (Rino, Charles L.); Straus, PR (Straus, Paul R.) |
|
Source: RADIO SCIENCE Volume: 46 Article Number: RS0D07 DOI: 10.1029/2010RS004591 Published: JUL 8 2011 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: We present the Radio Occultation Scintillation Simulator (ROSS), which uses the multiple phase screen method (MPS) to simulate the forward scatter of radio waves by irregularities in the equatorial ionosphere during radio occultation experiments. ROSS simulates propagation through equatorial plasma bubbles which are modeled as homogeneous electron density fluctuations modulated by a Chapman profile in altitude and a Gaussian window in the magnetic east-west direction. We adjust the parameters of the density model using electron density profiles derived from the ALTAIR incoherent scatter radar (9.4 degrees N, 167.5 degrees E, 4.3 degrees north dip), and space-to-ground observations of scintillation using VHF and GPS receivers that are colocated with the radar. We compare the simulated occultation scintillation to observations of scintillation from the CORISS instrument onboard the C/NOFS satellite during a radio occultation occurring near ALTAIR on 21 April 2009. The ratio of MPS predicted S(4) to CORISS observed S(4) throughout the F region altitudes of 240-350 km ranged between 0.86 and 1.14. |
|
Accession Number: WOS:000292610800001 |
|
ISSN: 0048-6604 |
|
Record 27 of 38 |
|
Title: Communications/Navigation Outage Forecasting System observational support for the equatorial E x B drift velocities associated with the four-cell tidal structures |
|
Author(s): Araujo-Pradere, EA (Araujo-Pradere, Eduardo A.); Anderson, DN (Anderson, David N.); Fedrizzi, M (Fedrizzi, Mariangel); Stoneback, R (Stoneback, Russell) |
|
Source: RADIO SCIENCE Volume: 46 Article Number: RS0D09 DOI: 10.1029/2010RS004557 Published: JUL 13 2011 |
|
Times Cited in Web of Science: 1 |
|
Total Times Cited: 1 |
|
Abstract: Previous studies have established the existence of a four-cell longitude pattern in equatorial F region ionospheric parameters such as total electron content and electron densities and in daytime, equatorial E x B drift velocities. This paper, for the first time, quantifies the longitude gradients in E x B drift associated with the four-cell tidal structures and confirms that these sharp gradients exist on a day-to-day basis. For this purpose, we use the Ion Velocity Meter (IVM) sensor on the Communications/Navigation Outage Forecasting System (C/NOFS) satellite to obtain the daytime, vertical E x B drift velocities at the magnetic equator as a function of longitude, local time, and season. The IVM sensor measures the E x B drift velocity in three dimensions; however, we only use the E x B drift observations perpendicular to B in the meridional plane. These observations can be used to obtain the vertical E x B drifts at the magnetic equator by mapping along the geomagnetic field line. The period initially selected for this work covers several days in October, March, and December 2009. We find, on a day-to-day basis, that (1) sharp E x B drift gradients of -1.3 m s(-1) deg(-1) exist in the western Pacific sector during equinox, (2) sharp E x B drift gradients of + 3 m s(-1) deg(-1) are observed in the eastern Pacific sector during equinox, and (3) sharp E x B drift gradients of -1.7 m s(-1) deg(-1) exist in the eastern Pacific sector during December solstice. |
|
Accession Number: WOS:000292837600001 |
|
ISSN: 0048-6604 |
|
Record 28 of 38 |
|
Title: Periodic structures in the equatorial ionosphere |
|
Author(s): Huang, CY (Huang, Cheryl Y.); Delay, SH (Delay, Susan H.); Roddy, PA (Roddy, Patrick A.); Sutton, EK (Sutton, Eric K.) |
|
Source: RADIO SCIENCE Volume: 46 Article Number: RS0D14 DOI: 10.1029/2010RS004569 Published: AUG 3 2011 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: The plasma densities detected by the Planar Langmuir Probe (PLP) on board the Communication/Navigation Outage Forecasting System (C/NOFS) satellite have been analyzed for the June 2008 period. This interval, which corresponds to one of the quietest periods in the space era, exhibited broad plasma decreases (BPDs) which we have reported previously. In order to treat the data quantitatively, we have detrended the PLP data by using the International Reference Ionosphere model to remove variations in density due to changes in spacecraft altitude and latitude along the orbit. In this paper we present results of a statistical analysis of C/NOFS detrended plasma densities during June 2008 as well as neutral densities from the Gravity Recovery and Climate Experiment measured during the same period. The results show periodic structures in both charged and neutral species, most evident in limited local times. These structures resemble wave-4 nonmigrating tides. BPDs persist in the detrended data and appear as one of the minima in the periodic signatures, most strikingly on the nightside. |
|
Accession Number: WOS:000293641000001 |
|
ISSN: 0048-6604 |
|
Record 29 of 38 |
|
Title: C/NOFS observations of the equatorial ionospheric electric field response to the 2009 major sudden stratospheric warming event |
|
Author(s): Rodrigues, FS (Rodrigues, F. S.); Crowley, G (Crowley, G.); Azeem, SMI (Azeem, S. M. I.); Heelis, RA (Heelis, R. A.) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 116 Article Number: A09316 DOI: 10.1029/2011JA016660 Published: SEP 22 2011 |
|
Times Cited in Web of Science: 2 |
|
Total Times Cited: 2 |
|
Abstract: We present new observations made by the Coupled Ion Neutral Dynamics Investigation (CINDI) Ion Velocity Meter (IVM) instrument onboard the Communication/Navigation Outage Forecasting System (C/NOFS) satellite that show the effects of the January 2009 sudden stratospheric warming (SSW) event on equatorial electric fields. We have used IVM observations to construct composite curves of mean equatorial vertical plasma drifts as a function of local time and longitude sector. These curves show large upward vertical drifts during morning hours and downward drifts during afternoon. Our analysis indicates that this pattern could be observed over the range of longitudes where adequate IVM measurements were available, from approximately 165 degrees E to about 315 degrees E longitude. A clear day-to-day, quasi-deterministic variability in the drifts is also observed, with the transition from upward to downward drifts occurring at increasing local times from 25 to 30 January 2009. The analysis also suggests some level of longitudinal variability in the magnitude of the drifts. These in-situ observations are in good agreement with previous ground-based measurements of the response of equatorial electric fields to SSW events. In particular, we found that IVM drift measurements centered around 285 degrees E depart significantly from climatological values but agree exceptionally well with ground-based measurements of vertical drifts made by the Jicamarca incoherent backscatter radar. Overall, the results agree well with previous studies of SSW events, demonstrate the usefulness of the IVM observations and motivate further studies of the variability of the equatorial ionosphere using C/NOFS. |
|
Accession Number: WOS:000295262000002 |
|
ISSN: 0148-0227 |
|
Record 30 of 38 |
|
Title: Assimilative modeling of observed postmidnight equatorial plasma depletions in June 2008 |
|
Author(s): Su, YJ (Su, Y. -J.); Retterer, JM (Retterer, J. M.); Pfaff, RF (Pfaff, R. F.); Roddy, PA (Roddy, P. A.); de La Beaujardiere, O (de La Beaujardiere, O.); Ballenthin, JO (Ballenthin, J. O.) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 116 Article Number: A09318 DOI: 10.1029/2011JA016772 Published: SEP 22 2011 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: The Communications/Navigation Outage Forecasting System (C/NOFS) satellite observed large-scale density depletions at postmidnight and early morning local times in the Northern Hemisphere summer during solar minimum conditions. Using electric field data obtained from the vector electric field instrument (VEFI) as input, the assimilative physics-based model (PBMOD) qualitatively reproduced more than 70% of the large-scale density depletions observed by the Planar Langmuir Probe (PLP) onboard C/NOFS. In contrast, the use of a climatological specification of plasma drifts in the model produces no plasma depletions at night. Results from a one-month statistical study, we found that the large-scale depletion structures most often occur near longitudes of 60 degrees, 140 degrees, and 330 degrees, suggesting that these depletions may be associated with nonmigrating atmospheric tides, although the generation mechanisms of eastward electric fields at postmidnight local times are still uncertain. In this paper, densities obtained from both assimilation and climatology for the entire month of June 2008 are compared with PLP data from C/NOFS and the Challenging Minisatellite Payload (CHAMP), as well as special sensor ionospheric plasma drift/scintillation meter (SSIES) measurements from the Defense Meteorological Satellite Program (DMSP) satellites. Our statistical study has shown that, on average, the densities obtained by the PBMOD when it assimilates VEFI electric fields agree better with observed background densities than when PBMOD uses climatological electric fields. |
|
Accession Number: WOS:000295262000003 |
|
ISSN: 0148-0227 |
|
Record 31 of 38 |
|
Title: Observations of low-latitude plasma density enhancements and their associated plasma drifts |
|
Author(s): Klenzing, JH (Klenzing, J. H.); Rowland, DE (Rowland, D. E.); Pfaff, RF (Pfaff, R. F.); Le, G (Le, G.); Freudenreich, H (Freudenreich, H.); Haaser, RA (Haaser, R. A.); Burrell, AG (Burrell, A. G.); Stoneback, RA (Stoneback, R. A.); Coley, WR (Coley, W. R.); Heelis, RA (Heelis, R. A.) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 116 Article Number: A09324 DOI: 10.1029/2011JA016711 Published: SEP 28 2011 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: Plasma density structures are frequently encountered in the nighttime low-latitude ionosphere by probes on the Communication/Navigation Outage Forecasting System (C/NOFS) satellite. Of particular interest to us here are plasma density enhancements, which are typically observed +/- 15 degrees away from the magnetic equator. The low inclination of the C/NOFS satellite offers an unprecedented opportunity to examine these structures and their associated electric fields and plasma velocities, including their field-aligned components, along an east-west trajectory. Among other observations, the data reveal a clear asymmetry in the velocity structure within and around these density enhancements. Previous data have shown that the peak perturbation in drift velocity associated with a density enhancement occurs simultaneously both perpendicular and parallel to the magnetic field, while the results in this paper show that the peak perturbation in parallel flow typically occurs 25-100 km to the east of the peak perpendicular flow. The absence of such a longitudinal offset in previous observations suggests that multiple physical mechanisms may be responsible for creating plasma density enhancements as observed by satellite-borne instrumentation. |
|
Accession Number: WOS:000295531800008 |
|
ISSN: 0148-0227 |
|
Record 32 of 38 |
|
Title: Using TEC and radio scintillation data from the CITRIS radio beacon receiver to study low and midlatitude ionospheric irregularities |
|
Author(s): Siefring, CL (Siefring, Carl L.); Bernhardt, PA (Bernhardt, Paul A.); Koch, DE (Koch, Douglas E.); Galysh, IJ (Galysh, Ivan J.) |
|
Source: RADIO SCIENCE Volume: 46 Article Number: RS0D19 DOI: 10.1029/2010RS004585 Published: OCT 15 2011 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: Unique data on ionospheric plasma irregularities from the Naval Research Laboratory Scintillation and TEC Receiver in Space (CITRIS) instrument is presented. CITRIS is a multiband receiver that recorded Total Electron Content (TEC) and radio scintillations from Low-Earth Orbit (LEO) on STPSat1. The 555 +/- 5 km altitude 35 inclination orbit covers low and midlatitudes. The measurements require propagation from a transmitter to a receiver through the F region plasma. CITRIS used both 1) satellite beacons in LEO and 2) the French sponsored global network of ground-based Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) beacons. This paper is both a brief review of the CITRIS experiment and the first combined TEC and scintillation study of ionospheric irregularities using a satellite-borne beacon receiver. It primarily focuses on CITRIS/DORIS observations and is a case study of the ionospheric irregularities and associated scintillation characteristics at 401.25 MHz during the 2008 equinox solar minimum. In addition, CITRIS was operated in a complementary fashion with the Communication/Navigations Outages Forecasting System (C/NOFS) satellite during C/NOFS' first year of operations and comparison with measured C/NOFS irregularity characteristics are made. Several types of irregularities have been studied including Spread-F and the newly discovered dawn-side depletions. |
|
Accession Number: WOS:000295984600002 |
|
ISSN: 0048-6604 |
|
Record 33 of 38 |
|
Title: C/NOFS satellite observations of equatorial ionospheric plasma structures supported by multiple ground-based diagnostics in October 2008 |
|
Author(s): Nishioka, M (Nishioka, M.); Basu, S (Basu, Su.); Basu, S (Basu, S.); Valladares, CE (Valladares, C. E.); Sheehan, RE (Sheehan, R. E.); Roddy, PA (Roddy, P. A.); Groves, KM (Groves, K. M.) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 116 Article Number: A10323 DOI: 10.1029/2011JA016446 Published: OCT 28 2011 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: In early October 2008, the C/NOFS satellite orbited near the magnetic equator at its perigee altitude of similar to 400 km at dusk in the Peruvian sector. This provided an ideal opportunity for a comparison, under the current very low solar flux condition, of equatorial ionospheric disturbances observed with the Communication/Navigation Outage Forecasting System (C/NOFS) in situ measurements and ground-based observations available near Jicamarca Observatory. The primary objective was the comparison of plasma density disturbances measured by a Planar Langmuir Probe (PLP) instrument on the C/NOFS satellite with VHF scintillation activity at Ancon near Jicamarca for this period. Here we discuss in detail two extreme cases: one in which severe in situ disturbances were accompanied by mild scintillation on a particular day, namely, 10 October while there was little in situ disturbance with strong scintillation on 5 October. This apparent contradiction was diagnosed further by a latitudinal ground-based GPS network at Peruvian longitudes, a Digisonde, and the incoherent scatter radar (ISR) at Jicamarca. The crucial distinction was provided by the behavior of the equatorial ionization anomaly (EIA). The EIA was well-developed on the day having severe in situ disturbances (10 Oct). This led to lower equatorial plasma density and total electron content (TEC) at the equator and consequently reduced the scintillations detected at Ancon. On the other hand, on the day with severe scintillations (5 Oct), the EIA was not so well developed as on 10 October, leading to relatively higher equatorial plasma density and TEC. Consequently the severe scintillations at Ancon were likely caused by ionospheric structure located below the altitude of C/NOFS. The NRL SAMI2 model was utilized to gain a greater understanding of the role of neutral winds and electric fields in reproducing the TEC as a function of latitude for both classes of irregularities. Spectral studies with high resolution in situ PLP data were also performed. The power law spectra within the plasma bubbles showed two slopes: the low frequency slope being similar to-5/3 and the high frequency similar to-5 with a break around lambda = 70 m. This particular type of two-slope spectra may be related to the extremely low solar activity and its impact on ion composition and temperature. |
|
Accession Number: WOS:000296355700001 |
|
ISSN: 0148-0227 |
|
Record 34 of 38 |
|
Title: Initial Studies with the Lightning Detector on the C/NOFS Satellite, and Cross Validation with WWLLN |
|
Author(s): Jacobson, AR (Jacobson, Abram R.); Holzworth, RH (Holzworth, Robert H.); McCarthy, MP (McCarthy, Michael P.); Pfaff, RF (Pfaff, Robert F.) |
|
Source: JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY Volume: 28 Issue: 11 Pages: 1423-1435 DOI: 10.1175/JTECH-D-11-00047.1 Published: NOV 2011 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: The lightning detector (LD) on the Communications/Navigation Outage Forecast System (C/NOFS) satellite uses a pair of silicon photodiodes, viewing each flank at right angles to the satellite track over an extended field of view. The data product is a report every 1/2 s of the number of digitizer cycles (125 mu s each) for which the detected power was in predefined ranges. The performance of this system over the first 2.5 years of the C/NOFS mission is discussed, statistics of its lightning observations are presented, and a statistical cross validation using the World-Wide Lightning Location Network (WWLLN) as a ground truth is provided. It is found that the LD reports of lightning, despite their blunt timing (1/2 s), show correlation with strokes detected and located by WWLLN. The irradiance of these strokes lies on the high-power flank of the irradiance distribution seen earlier by the FORTE satellite. Thus, the LD thresholds favor high-power lightning; it is shown that the closest portion of the field of view is more likely to provide WWLLN coincidences than is the furthest portion of the field of view. Statistics of lightning incidence are examined at low latitudes, versus longitude, and distributions that are consistent with those established earlier by the OTD and LIS instruments are retrieved. Finally, the longitude dependence of the irradiance per stroke is examined and the ways in which it differs between the three major lightning "hot spots" is explored. It is observed that the radiance per stroke over the Congo Basin is lower than that over the other two hot spots (Maritime Continent/South Asia and the Americas), consistent with earlier observations by the OTD imager. |
|
Accession Number: WOS:000297484700005 |
|
ISSN: 0739-0572 |
|
Record 35 of 38 |
|
Title: Latitude and local time variations of topside magnetic field-aligned ion drifts at solar minimum |
|
Author(s): Burrell, AG (Burrell, A. G.); Heelis, RA (Heelis, R. A.); Stoneback, RA (Stoneback, R. A.) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 116 Article Number: A11312 DOI: 10.1029/2011JA016715 Published: NOV 11 2011 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: The movement of ions along terrestrial magnetic field lines frequently causes the redistribution of ionization between northern and southern hemispheres. This behavior is known as interhemispheric transport and is an important source of coupling between the ion and neutral gases in the upper atmosphere. The Communications/Navigation Outage Forecast System (C/NOFS) satellite and the Coupled Ion Neutral Dynamics Investigation (CINDI) provide an opportunity to directly measure ion velocities and ion densities in the topside ionosphere, facilitating the study of the field-aligned ion motions near the equator. Using data from 2008 and 2009, the field-aligned ion velocities shows the presence of and variations in the interhemispheric transport during this extreme solar minimum. Solar local time and corrected magnetic latitude variations in field-aligned plasma transport at equinox and solstice are examined for a fixed longitude region and the consistency or the observed trends are compared to the expected behavior of F region neutral winds. |
|
Accession Number: WOS:000297063100002 |
|
ISSN: 0148-0227 |
|
Record 36 of 38 |
|
Title: Satellite observations of Schumann resonances in the Earth's ionosphere |
|
Author(s): Simoes, F (Simoes, Fernando); Pfaff, R (Pfaff, Robert); Freudenreich, H (Freudenreich, Henry) |
|
Source: GEOPHYSICAL RESEARCH LETTERS Volume: 38 Article Number: L22101 DOI: 10.1029/2011GL049668 Published: NOV 16 2011 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: Using electric field measurements gathered on the C/NOFS satellite, we report, Schumann resonance signatures detected in space, well beyond the upper boundary of the resonant cavity formed by the earth's surface and the lower edge of the ionosphere. The resonances are routinely observed in the satellite ELF data during nighttime conditions within the altitude region of 400-850 km sampled by the satellite. They exhibit the distinctive frequency patterns predicted for Schumann resonances and are consistent with the corresponding frequency characteristics of ground-based observations of this phenomenon. The observations of Schumann resonances in space support a leaky cavity interpretation of the ionosphere and call for revisions of models of extremely low frequency wave propagation in the ionosphere. They suggest new remote sensing capabilities for investigating atmospheric electricity on Earth and other planets. Citation: Simoes, F., R. Pfaff, and H. Freudenreich (2011), Satellite observations of Schumann resonances in the Earth's ionosphere, Geophys. Res. Lett., 38, L22101, doi: 10.1029/2011GL049668. |
|
Accession Number: WOS:000297258000003 |
|
ISSN: 0094-8276 |
|
Record 37 of 38 |
|
Title: On postmidnight low-latitude ionospheric irregularities during solar minimum: 2. C/NOFS observations and comparisons with the Equatorial Atmosphere Radar |
|
Author(s): Yokoyama, T (Yokoyama, T.); Pfaff, RF (Pfaff, R. F.); Roddy, PA (Roddy, P. A.); Yamamoto, M (Yamamoto, M.); Otsuka, Y (Otsuka, Y.) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 116 Article Number: A11326 DOI: 10.1029/2011JA016798 Published: NOV 22 2011 |
|
Times Cited in Web of Science: 1 |
|
Total Times Cited: 1 |
|
Abstract: A detailed comparison between the observations of the Communication/Navigation Outage Forecasting System (C/NOFS) satellite and the 47 MHz Equatorial Atmosphere Radar (EAR) in West Sumatra, Indonesia (10.36 degrees S dip latitude) on the postmidnight irregularities is presented. The zonal and meridional E x B drift velocities measured by the vector electric field instrument on the C/NOFS are consistent with the westward propagation of backscatter echoes and the line-of-sight Doppler velocities observed with the EAR, respectively. The plasma density depletions are observed in the postmidnight sector for several consecutive orbits, which suggests the depletions grow slowly during the premidnight period and reach the spacecraft altitude around local midnight. The convergence of the equatorward wind which could be responsible for the midnight temperature maximum may produce a preferable condition for the growth of the Rayleigh-Taylor instability around midnight. Electric field fluctuations of medium-scale traveling ionospheric disturbances may play an important role in seeding the instability. Both equatorial and midlatitude-type plasma instabilities could be operational at the EAR latitude sector, which together would foster a high occurrence of postmidnight irregularities during solar minimum. |
|
Accession Number: WOS:000297420400002 |
|
ISSN: 0148-0227 |
|
Record 38 of 38 |
|
Title: C/NOFS measurements of magnetic perturbations in the low-latitude ionosphere during magnetic storms |
|
Author(s): Le, G (Le, Guan); Burke, WJ (Burke, William J.); Pfaff, RF (Pfaff, Robert F.); Freudenreich, H (Freudenreich, Henry); Maus, S (Maus, Stefan); Luhr, H (Luehr, Hermann) |
|
Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 116 Article Number: A12230 DOI: 10.1029/2011JA017026 Published: DEC 28 2011 |
|
Times Cited in Web of Science: 0 |
|
Total Times Cited: 0 |
|
Abstract: The Vector Electric Field Investigation suite on the C/NOFS satellite includes a fluxgate magnetometer to monitor the Earth's magnetic fields in the low-latitude ionosphere. Measurements yield full magnetic vectors every second over the range of +/- 45,000 nT with a one-bit resolution of 1.37 nT ( 16 bit A/D) in each component. The sensor's primary responsibility is to support calculations of both V x B and E x B with greater accuracy than can be obtained using standard magnetic field models. The data also contain information about large-scale current systems that, when analyzed in conjunction with electric field measurements, promise to significantly expand understanding of equatorial electrodynamics. We first compare in situ measurements with the POMME (Potsdam Magnetic Model of the Earth) model to establish in-flight sensor "calibrations" and to compute magnetic residuals. At low latitudes the residuals are predominately products of the storm time ring current. Since C/NOFS provides a complete coverage of all local times every 97 min, magnetic field data allow studies of the temporal evolution and local time variations of storm time ring current. The analysis demonstrates the feasibility of using instrumented spacecraft in low-inclination orbits to extract a timely proxy for the provisional Dst index and to specify the ring current's evolution. |
|
Accession Number: WOS:000298761300006 |
|
ISSN: 0148-0227 |