scholarly journals Characteristics of the ionospheric variability as a function of season, latitude, local time, and geomagnetic activity

Radio Science ◽  
2005 ◽  
Vol 40 (5) ◽  
pp. n/a-n/a ◽  
Author(s):  
E. A. Araujo-Pradere ◽  
T. J. Fuller-Rowell ◽  
M. V. Codrescu ◽  
D. Bilitza
Keyword(s):  
Local Time ◽  
Geomagnetic Activity ◽  
Ionospheric Variability

scholarly journals Specification of > 2 MeV electron flux as a function of local time and geomagnetic activity at geosynchronous orbit

Space Weather ◽  
2014 ◽  
Vol 12 (7) ◽  
pp. 470-486 ◽  
Author(s):  
Yi-Jiun Su ◽  
Jack M. Quinn ◽  
W. Robert Johnston ◽  
James P. McCollough ◽  
Michael J. Starks
Keyword(s):  
Local Time ◽  
Geomagnetic Activity ◽  
Electron Flux ◽  
Geosynchronous Orbit

scholarly journals The equatorward wall of the subauroral trough in the afternoon/evening sector

2007 ◽  
Vol 25 (3) ◽  
pp. 645-659 ◽  
Author(s):  
G. W. Prölss
Keyword(s):  
Numerical Simulation ◽  
Local Time ◽  
Geomagnetic Activity ◽  
Complex Phenomenon ◽  
Anomalous Increase ◽  
Secondary Importance ◽  
Evening Sector ◽  
Longitudinal Variations ◽  
Specific Part ◽  
Latitudinal Profile

Abstract. Although ionospheric troughs are a very important feature of the subauroral ionosphere, many of their properties remain incompletely documented and understood. Here Dynamics Explorer-2 satellite data are used to investigate one specific part of this complex phenomenon, namely its equatorward wall. We find that in the afternoon/evening sector of the Northern Hemisphere the location of this density drop depends primarily on the level of geomagnetic activity and magnetic local time. Longitudinal variations are only of secondary importance. A formula is derived which summarizes these variations. The magnitude of the density drop in the trough wall depends primarily on altitude and longitude, and to a lesser degree on local time and geomagnetic activity. These variations are also described quantitatively. Using a superposed epoch type of averaging procedure, a mean latitudinal profile of the trough wall is derived. No anomalous increase in the density at the equatorward edge of the trough is observed. There is, however, a significant increase in the electron temperature at the location of the density drop. Our results are important for the empirical description and numerical simulation of ionospheric troughs. They also may be used to define the boundary between middle and subauroral latitudes.

scholarly journals Use of radio occultation to probe the high latitude ionosphere

2015 ◽  
Vol 8 (2) ◽  
pp. 2093-2121
Author(s):  
A. J. Mannucci ◽  
B. T. Tsurutani ◽  
O. Verkhoglyadova ◽  
A. Komjathy ◽  
X. Pi
Keyword(s):  
Electron Density ◽  
Local Time ◽  
Geomagnetic Activity ◽  
High Latitude ◽  
Geomagnetic Storms ◽  
Scientific Information ◽  
Main Phase ◽  
Local Times ◽  
Clear Correlation ◽  
E Region

Abstract. We have explored the use of COSMIC data to provide valuable scientific information on the ionospheric impacts of energetic particle precipitation during geomagnetic storms. Ionospheric electron density in the E region, and hence ionospheric conductivity, is significantly altered by precipitating particles from the magnetosphere. This has global impacts on the thermosphere-ionosphere because of the important role of conductivity on high latitude Joule heating. Two high-speed stream (HSS) and two coronal mass ejection (CME) storms are examined with the COSMIC data. We find clear correlation between geomagnetic activity and electron density retrievals from COSMIC. At nighttime local times, the number of profiles with maximum electron densities in the E layer (below 200 km altitude) is well correlated with geomagnetic activity. We interpret this to mean that electron density increases due to precipitation are captured by the COSMIC profiles. These "E layer dominant ionosphere" (ELDI) profiles have geomagnetic latitudes that are consistent with climatological models of the auroral location. For the two HSS storms, that occurred in May of 2011 and 2012, a strong hemispheric asymmetry is observed, with nearly all the ELDI profiles found in the southern, less sunlit, hemisphere. Stronger aurora and precipitation have been observed before in winter hemispheres, but the degree of asymmetry deserves further study. For the two CME storms, occurring in July and November of 2012, large increases in the number of ELDI profiles are found starting in the storm's main phase but continuing for several days into the recovery phase. Analysis of the COSMIC profiles was extended to all local times for the July 2012 CME storm by relaxing the ELDI criterion and instead visually inspecting all profiles above 50° magnetic latitude for signatures of precipitation in the E region. For nine days during the July 2012 period, we find a signature of precipitation occurs nearly uniformly in local time, although the magnitude of electron density increase may vary with local time. The latitudinal extent of the precipitation layers is generally consistent with auroral climatology. However, after the storm main phase on 14 July 2012, the precipitation tended to be somewhat more equatorward than predicted by the climatology (by about 5–10° latitude). We conclude that, if analyzed appropriately, high latitude COSMIC profiles have the potential to contribute to our understanding of MI coupling processes and extend and improve existing models of the auroral region.

Geomagnetic activity effects on CO2‐driven trend in the thermosphere and ionosphere:  ideal model experiments with GAIA

2021 ◽  
Author(s):  
Huixin Liu ◽  
Chihiro Tao ◽  
Hidekatsu Jin
Keyword(s):  
Local Time ◽  
Geomagnetic Activity ◽  
Space Weather ◽  
Mass Density ◽  
Activity Level ◽  
Ideal Model ◽  
Model Framework ◽  
Preliminary Model ◽  
Geomagnetic Activities ◽  
Weather Impacts

<p>We examine impacts of geomagnetic activity on CO<sub>2</sub>-driven trend in the Ionosphere and Thermosphere (IT) using the GAIA whole atmosphere model. The model reveals three salient features. (1) Geomagnetic activities usually weakens the CO<sub>2</sub>-driven trend at a fixed altitude. Among the IT parameters analyzed, the thermosphere mass density is the most robust indicator for CO<sub>2</sub> cooling effect even with geomagnetic activity influences. (2) Geomagnetic activities can either strengthen or weaken the CO<sub>2</sub>-driven trend in hmF2 and NmF2, depending on local time and latitudes. This renders the widely used linear fitting methods invalid for removing geomagnetic effects from observations. (3) An interdependency exists between the efficiency of CO<sub>2</sub> forcing and geomagnetic forcing, with the former enhances at lower geomagnetic activity level, while the latter enhances at higher CO<sub>2</sub> concentration. This could imply that the CO<sub>2</sub>-driven trend would accelerate in periods of declining geomagnetic activity, while magnetic storms may have larger space weather impacts in the future with increasing CO<sub>2</sub>. These findings provide a preliminary model framework to understand interactions between the CO<sub>2</sub> forcing from below and the geomagnetic forcing from above.</p>

Ionosphere response to recurrent geomagnetic activity: Local time dependency

2010 ◽  
Vol 115 (A2) ◽  
pp. n/a-n/a ◽  
Author(s):  
N. M. Pedatella ◽  
J. Lei ◽  
J. P. Thayer ◽  
J. M. Forbes
Keyword(s):  
Local Time ◽  
Geomagnetic Activity ◽  
Time Dependency

scholarly journals Use of radio occultation to probe the high-latitude ionosphere

2015 ◽  
Vol 8 (7) ◽  
pp. 2789-2800 ◽  
Author(s):  
A. J. Mannucci ◽  
B. T. Tsurutani ◽  
O. Verkhoglyadova ◽  
A. Komjathy ◽  
X. Pi
Keyword(s):  
Electron Density ◽  
Local Time ◽  
Geomagnetic Activity ◽  
High Latitude ◽  
Geomagnetic Storms ◽  
Scientific Information ◽  
Main Phase ◽  
Local Times ◽  
Clear Correlation ◽  
E Region

Abstract. We have explored the use of COSMIC data to provide valuable scientific information on the ionospheric impacts of energetic particle precipitation during geomagnetic storms. Ionospheric electron density in the E region, and hence ionospheric conductivity, is significantly altered by precipitating particles from the magnetosphere. This has global impacts on the thermosphere–ionosphere because of the important role of conductivity on high-latitude Joule heating. Two high-speed stream (HSS) and two coronal mass ejection (CME) storms are examined with the COSMIC data. We find clear correlation between geomagnetic activity and electron density retrievals from COSMIC. At nighttime local times, the number of profiles with maximum electron densities in the E layer (below 200 km altitude) is well correlated with geomagnetic activity. We interpret this to mean that electron density increases due to precipitation are captured by the COSMIC profiles. These "E-layer-dominant ionosphere" (ELDI) profiles have geomagnetic latitudes that are consistent with climatological models of the auroral location. For the two HSS storms that occurred in May of 2011 and 2012, a strong hemispheric asymmetry is observed, with nearly all the ELDI profiles found in the Southern, less sunlit, Hemisphere. Stronger aurora and precipitation have been observed before in winter hemispheres, but the degree of asymmetry deserves further study. For the two CME storms, occurring in July and November of 2012, large increases in the number of ELDI profiles are found starting in the storm's main phase but continuing for several days into the recovery phase. Analysis of the COSMIC profiles was extended to all local times for the July 2012 CME storm by relaxing the ELDI criterion and instead visually inspecting all profiles above 50° magnetic latitude for signatures of precipitation in the E region. For 9 days during the July 2012 period, we find a signature of precipitation occurs nearly uniformly in local time, although the magnitude of electron density increase may vary with local time. The latitudinal extent of the precipitation layers is generally consistent with auroral climatology. However, after the storm main phase on 14 July 2012 the precipitation tended to be somewhat more equatorward than the climatology (by about 5–10° latitude) and equatorward of the auroral boundary data acquired from the SSUSI sensor onboard the F18 DMSP satellite. We conclude that, if analyzed appropriately, high-latitude COSMIC profiles have the potential to contribute to our understanding of MI coupling processes and extend and improve existing models of the auroral region.

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