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| Titel |
Use of radio occultation to probe the high-latitude ionosphere |
| VerfasserIn |
A. J. Mannucci, B. T. Tsurutani, O. Verkhoglyadova, A. Komjathy, X. Pi |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 7 ; Nr. 8, no. 7 (2015-07-16), S.2789-2800 |
| Datensatznummer |
250116480
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| Publikation (Nr.) |
 copernicus.org/amt-8-2789-2015.pdf |
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| Zusammenfassung |
| 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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