scholarly journals Analysis of plasmaspheric plumes: CLUSTER and IMAGE observations

2006 ◽  
Vol 24 (6) ◽  
pp. 1737-1758 ◽  
Author(s):  
F. Darrouzet ◽  
J. De Keyser ◽  
P. M. E. Décréau ◽  
D. L. Gallagher ◽  
V. Pierrard ◽  
...  
Keyword(s):  
High Time Resolution ◽  
Total Electron Density ◽  
Density Profiles ◽  
Total Electron ◽  
In Situ Data ◽  
Spacecraft Potential ◽  
Point Analysis ◽  
Boundary Velocity ◽  
Electron Density Profiles

Abstract. Plasmaspheric plumes have been routinely observed by CLUSTER and IMAGE. The CLUSTER mission provides high time resolution four-point measurements of the plasmasphere near perigee. Total electron density profiles have been derived from the electron plasma frequency identified by the WHISPER sounder supplemented, in-between soundings, by relative variations of the spacecraft potential measured by the electric field instrument EFW; ion velocity is also measured onboard these satellites. The EUV imager onboard the IMAGE spacecraft provides global images of the plasmasphere with a spatial resolution of 0.1 RE every 10 min; such images acquired near apogee from high above the pole show the geometry of plasmaspheric plumes, their evolution and motion. We present coordinated observations of three plume events and compare CLUSTER in-situ data with global images of the plasmasphere obtained by IMAGE. In particular, we study the geometry and the orientation of plasmaspheric plumes by using four-point analysis methods. We compare several aspects of plume motion as determined by different methods: (i) inner and outer plume boundary velocity calculated from time delays of this boundary as observed by the wave experiment WHISPER on the four spacecraft, (ii) drift velocity measured by the electron drift instrument EDI onboard CLUSTER and (iii) global velocity determined from successive EUV images. These different techniques consistently indicate that plasmaspheric plumes rotate around the Earth, with their foot fully co-rotating, but with their tip rotating slower and moving farther out.

Determination Of Daytime Midlatitude Electron Density Profiles From Satellite UV And In-Situ Data

1988 ◽  
Author(s):  
D. T. Decker ◽  
J. M. Retterer ◽  
J. R. Jasperse ◽  
D. N. Anderson ◽  
R. W. Eastes ◽  
...  
Keyword(s):  
Electron Density ◽  
Density Profiles ◽  
In Situ Data ◽  
Electron Density Profiles

scholarly journals Density structures inside the plasmasphere: Cluster observations

2004 ◽  
Vol 22 (7) ◽  
pp. 2577-2585 ◽  
Author(s):  
F. Darrouzet ◽  
P. M. E. Décréau ◽  
J. De Keyser ◽  
A. Masson ◽  
D. L. Gallagher ◽  
...  
Keyword(s):  
Density Gradient ◽  
Time Delays ◽  
Statistical Study ◽  
Outer Boundary ◽  
Normal Velocity ◽  
Density Profiles ◽  
Density Measurements ◽  
Image Satellite ◽  
Electron Density Profiles

Abstract. The electron density profiles derived from the EFW and WHISPER instruments on board the four Cluster spacecraft reveal density structures inside the plasmasphere and at its outer boundary, the plasmapause. We have conducted a statistical study to characterize these density structures. We focus on the plasmasphere crossing on 11 April 2002, during which Cluster observed several density irregularities inside the plasmasphere, as well as a plasmaspheric plume. We derive the density gradient vectors from simultaneous density measurements by the four spacecraft. We also determine the normal velocity of the boundaries of the plume and of the irregularities from the time delays between those boundaries in the four individual density profiles, assuming they are planar. These new observations yield novel insights about the occurrence of density irregularities, their geometry and their dynamics. These in-situ measurements are compared with global images of the plasmasphere from the EUV imager on board the IMAGE satellite.

Seismo-ionospheric precursors of the 14 November 2019 M7.1 Indonesia Earthquake detected by FORMOSAT-7/COSMIC-2

2020 ◽  
Author(s):  
Jann-Yenq Liu ◽  
Chi-Yen Lin ◽  
Fu-Yuan Chang ◽  
Yuh-Ing Chen
Keyword(s):  
Electron Density ◽  
Electric Fields ◽  
Radio Occultation ◽  
Electron Content ◽  
Ion Temperature ◽  
Density Profiles ◽  
Ion Density ◽  
Total Electron ◽  
Ion Velocity ◽  
Electron Density Profiles

<p>FORMOSAT-7/COSMIC-2 (F7/C2), with the mission orbit of 550 km altitude, 24-deg inclination, and a period of 97 minutes, was launched on 25 June 2019.  Tri-GNSS Radio occultation System (TGRS), Ion Velocity Meter (IVM), and RF beacon onboard F7/C2 six small satellites allow scientists to observe the plasma structure and dynamics in the mid-latitude, low-latitude, and equatorial ionosphere in detail.  F7/C2 TGRS sounds ionospheric RO (radio occultation) electron density profiles, while F7/C2 IVM probes the ion density, ion temperature, and ion velocity at the satellite altitude.  The F7/C2 electron density profiles and the ion density, ion temperature, and ion velocity, as well as the global ionospheric map (GIM) of the total electron content (TEC) derived from global ground-based GPS receivers are used to detect seismo-ionospheric precursors (SIPs) of the 14 November 2019 M7.1 Indonesia Earthquake.  The GIM TEC and F7/C2 RO NmF2 significantly increase specifically over the epicenter on 25-26 October, which indicates SIPs of the 14 November 2019 M7.1 Indonesia Earthquake being detected.  The F7/C2 RO electron density profiles upward motions suggest that the eastward electric fields have been enhanced during the SIP days of the 2019 M7.1 Indonesia earthquake.  The seismo-generated electric fields of the 2019 M7.1 Indonesia earthquake are 0.34-0.64 mV/m eastward.  The results demonstrate that F7/C2 can be employed to detect SIPs in the ionospheric plasma, which shall shed some light on earthquake prediction/forecast.</p>

scholarly journals Error analysis of Abel retrieved electron density profiles from radio occultation measurements

2010 ◽  
Vol 28 (1) ◽  
pp. 217-222 ◽  
Author(s):  
X. Yue ◽  
W. S. Schreiner ◽  
J. Lei ◽  
S. V. Sokolovskiy ◽  
C. Rocken ◽  
...  
Keyword(s):  
Electron Density ◽  
Radio Occultation ◽  
Electron Content ◽  
Electron Densities ◽  
Density Profiles ◽  
Total Electron ◽  
The North ◽  
Spring Equinox ◽  
Electron Density Profiles ◽  
Artificial Plasma

Abstract. This letter reports for the first time the simulated error distribution of radio occultation (RO) electron density profiles (EDPs) from the Abel inversion in a systematic way. Occultation events observed by the COSMIC satellites are simulated during the spring equinox of 2008 by calculating the integrated total electron content (TEC) along the COSMIC occultation paths with the "true" electron density from an empirical model. The retrieval errors are computed by comparing the retrieved EDPs with the "true" EDPs. The results show that the retrieved NmF2 and hmF2 are generally in good agreement with the true values, but the reliability of the retrieved electron density degrades in low latitude regions and at low altitudes. Specifically, the Abel retrieval method overestimates electron density to the north and south of the crests of the equatorial ionization anomaly (EIA), and introduces artificial plasma caves underneath the EIA crests. At lower altitudes (E- and F1-regions), it results in three pseudo peaks in daytime electron densities along the magnetic latitude and a pseudo trough in nighttime equatorial electron densities.

scholarly journals Deviations from model predictions in measured electron density profiles for low latitudes: A critique

2004 ◽  
Vol 43 (2) ◽  
pp. 165-172
Author(s):  
P. Muralikrishna ◽  
L. P. Vieira ◽  
M. A. Abdu ◽  
E. R. De Paula
Keyword(s):  
Electron Density ◽  
Density Profiles ◽  
Model Predictions ◽  
Low Latitudes ◽  
Electron Density Profiles

Se comparan los perfiles obtenidos in situ de las estaciones ecuatoriales de Brasil, usando pruebas de Langmuir y de Frecuencia de Alta Capacitancia, con las predicciones del modelo IRI, en el contexto de las distribuciones espectrales de las irregularidades observadas en la densidad del plasma. Se asume que las inestabilidades de Rayleigh-Taylor y la de Campo Cruzado, son las responsables de la generación de las irregularidades observadas en el plasma, y con ellas se estima el tiempo de crecimiento y el tamaño mínimo de las irregularidades que se observan en diferentes alturas para el perfil de densidad electrónica. Para ello se usan aproximaciones polinomiales simples para representar el perfil observado. La comparación entre las características de las irregularidades observadas del plasma con las esperadas a partir de la teoría nos puede dar información sobre la confiabilidad del perfil observado. La confiabilidad se vuelve particularmente importante de estimar debido a que las técnicas de medición de densidad electrónica se asocian a algunos problemas. Entonces se puede ver que si las desviaciones observadas del perfil comparadas con el modelo IRI son reales o no. De este estudio comparativo uno puede saber cuáles son los parámetros físicos responsables por las desviaciones observadas y sugerir mejoras en los métodos usados en las predicciones de IRI a bajas latitudes.

Extraction of electron density profiles with geostationary satellite-based GPS side lobe occultation signals

2020 ◽  
Author(s):  
Wenwen Li ◽  
Min Li ◽  
Qile Zhao ◽  
Chuang Shi ◽  
Rongxin Fang
Keyword(s):  
Electron Density ◽  
Side Lobe ◽  
Low Earth Orbit ◽  
Single Frequency ◽  
Earth Orbit ◽  
Electron Content ◽  
Density Profiles ◽  
Total Electron ◽  
Geo Satellite ◽  
Electron Density Profiles

<p>Electron density profiles (EDP) obtained by GNSS radio occultation (RO) technique can improve the primary ionospheric parameters. However, current studies mainly focused on GNSS RO measurements observed by low Earth orbit satellites, which can only estimate EDP at low altitudes typically below 1000 km. We investigated the GPS RO measurements recorded on the geostationary earth orbit (GEO) satellite TJS-2 (telecommunication technology test satellite II). To improve EDP derivation precision, the total electron content derived from TJS-2 single-frequency excess phase is refined by a moving average filter, which can smooth high-frequency errors and indicate higher precision over the single-difference technique. By comparison with the ground-based digisonde, the IRI 2016 model and the Constellation Observing System for Meteorology, Ionosphere, and Climate satellite (COSMIC) EDPs, the TJS-2 ionospheric EDPs show good agreement with correlation coefficients exceeding 0.8. The TJS-2 average NmF2 differences compared to digisondes and COSMIC results are 12.9% and 1.4%, respectively, while the hmF2 differences are 1.65 km and 1.76 km, respectively. With a GEO satellite such as TJS-2, the side lobe GPS RO signals can also be received, and they are employed to estimate electron densities up to several thousand kilometers in height for the first time in this contribution. Our results also reveal that GEO-based RO signals can estimate EDPs at specific locations with daily repeatability, which makes it a very suitable technique for routinely monitoring EDP variations</p>

Mars’ ionopause characterization based on MAVEN and Mars Express observations

2020 ◽  
Author(s):  
Beatriz Sanchez-Cano ◽  
Clara Narvaez ◽  
Mark Lester ◽  
Michael Mendillo ◽  
Majd Mayyasi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Fields ◽  
Electron Density ◽  
Dynamic Pressure ◽  
Solar Wind Dynamic Pressure ◽  
Thermal Pressure ◽  
Density Profiles ◽  
Electron Density Profiles

<p>The ionopause is a tangential discontinuity in the ionospheric thermal plasma density profile that marks the upper boundary of the ionosphere for unmagnetized planets. Since only Venus and Mars have no global “dipole” magnetic fields, ionopauses are unique to those planets. For Venus, the ionopause formation is well characterized because the thermal pressure of the ionosphere is usually larger than the solar wind dynamic pressure. For Mars, however, the maximum thermal pressure of the ionosphere is usually insufficient to balance the total pressure in the overlying magnetic pileup boundary. Therefore, the Martian ionopause is not always formed, and when it does, it is highly structured and is located at different altitudes. In this study, we characterise the Martian ionopause formation from the point of view of the electron density and electron temperature, as well as the thermal, magnetic and dynamic pressures. The objective is to investigate under which circumstances the Martian ionopause is formed, both over and far from crustal magnetic fields, and compare to the Venus’ case. We use several multi-plasma and magnetic field in-situ observations from the three deep dip campaigns of the MAVEN mission that occurred on the dayside of Mars (near subsolar point), as well as in-situ solar wind plasma observations from the Mars Express mission. We find that that 36% of the electron density profiles over strong crustal magnetic field regions had an ionopause event in contrast to the 54% of electron density profiles far from strong crustal magnetic field regions. We also find that the topside ionosphere is typically magnetized at mostly all altitudes. The ionopause, if formed, occurs where the total ionospheric pressure (magnetic+thermal) equals the upstream solar wind dynamic pressure.</p>

scholarly journals Polar observations of electron density distribution in the Earth’s magnetosphere. 1. Statistical results

2002 ◽  
Vol 20 (11) ◽  
pp. 1711-1724 ◽  
Author(s):  
H. Laakso ◽  
R. Pfaff ◽  
P. Janhunen
Keyword(s):  
Electron Density ◽  
Individual Case ◽  
Auroral Zone ◽  
Average Density ◽  
High Time Resolution ◽  
Polar Cap ◽  
Total Electron Density ◽  
Total Electron ◽  
Magnetospheric Configuration And Dynamics ◽  
Order Of Magnitude

Abstract. Forty-five months of continuous spacecraft potential measurements from the Polar satellite are used to study the average electron density in the magnetosphere and its dependence on geomagnetic activity and season. These measurements offer a straightforward, passive method for monitoring the total electron density in the magnetosphere, with high time resolution and a density range that covers many orders of magnitude. Within its polar orbit with geocentric perigee and apogee of 1.8 and 9.0 RE, respectively, Polar encounters a number of key plasma regions of the magnetosphere, such as the polar cap, cusp, plasmapause, and auroral zone that are clearly identified in the statistical averages presented here. The polar cap density behaves quite systematically with season. At low distance (~2 RE), the density is an order of magnitude higher in summer than in winter; at high distance (>4 RE), the variation is somewhat smaller. Along a magnetic field line the density declines between these two altitudes by a factor of 10–20 in winter and by a factor of 200–1000 in summer. A likely explanation for the large gradient in the summer is a high density of heavy ions that are gravitationally bound in the low-altitude polar cap. The geomagnetic effects are also significant in the polar cap, with the average density being an order of magnitude larger for high Kp; for an individual case, the polar cap density may increase even more dramatically. The plasma density in the cusp is controlled primarily by the solar wind variables, but nevertheless, they can be characterized to some extent in terms of the Kp index. We also investigate the local time variation of the average density at the geosynchronous distance that appears to be in accordance with previous geostationary observations. The average density decreases with increasing Kp at all MLT sectors, except at 14–17 MLT, where the average density remains constant. At all MLT sectors the range of the density varies by more than 3 orders of magnitude, since the geostationary orbit may cut through different plasma regions, such as the plasma sheet, trough, and plasmasphere.Key words. Magnetospheric physics (magnetospheric configuration and dynamics; plasmasphere; polar cap phenomena)

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