Thermospheric density structures over the polar regions observed with CHAMP
We report on the unexpected detection of considerable structure in high latitude thermospheric densities, as derived from an accelerometer onboard the CHAMP satellite. The width of the structures, which can either be maxima or minima, varies between a few hundred km and 2000 km. The amplitudes of...
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doaj-104e9e151259455184c9a22c10fdc2af2020-11-24T23:55:13ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762005-07-01231659167210.5194/angeo-23-1659-2005Thermospheric density structures over the polar regions observed with CHAMPK. Schlegel0H. Lühr1J.-P. St.-Maurice2G. Crowley3C. Hackert4Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, GermanyGeoForschungsZentrum Potsdam, Potsdam, GermanyInstitute for Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, CanadaSouthwest Research Institute, San Antonio, TX, USASouthwest Research Institute, San Antonio, TX, USAWe report on the unexpected detection of considerable structure in high latitude thermospheric densities, as derived from an accelerometer onboard the CHAMP satellite. The width of the structures, which can either be maxima or minima, varies between a few hundred km and 2000 km. The amplitudes of these density extrema can reach 50% of ambient. Maxima cluster around 75° (N and S), while minima are found closer to the poles. In a magnetic latitude-magnetic local time frame the maxima are found mainly around the cusp region. Overall, the observed structures somewhat resemble so-called density cells previously found in model calculations. However the models generate their cells around 140–300 km altitude and show little, if any remnant at 400 km or above. This has to be contrasted with the fact that the CHAMP observations were obtained near 430 km altitude. We have explored Joule heating as a possible mechanism for the generation of the structures, at least in density enhancement regions, using Hall currents measured on CHAMP and simultaneous incoherent scatter measurements with EISCAT. However, the electric fields were usually quite small during the period of observation, making the quest for an explanation for the structures all the more challenging.<br><br> <b>Keywords.</b> Meteorology and atmospheric dynamics (Thermospheric dynamics) – Magnetospheric physics (Polar cap phenomena) – Atmospheric composition and structure (Pressure, density, and temperature)https://www.ann-geophys.net/23/1659/2005/angeo-23-1659-2005.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
K. Schlegel H. Lühr J.-P. St.-Maurice G. Crowley C. Hackert |
spellingShingle |
K. Schlegel H. Lühr J.-P. St.-Maurice G. Crowley C. Hackert Thermospheric density structures over the polar regions observed with CHAMP Annales Geophysicae |
author_facet |
K. Schlegel H. Lühr J.-P. St.-Maurice G. Crowley C. Hackert |
author_sort |
K. Schlegel |
title |
Thermospheric density structures over the polar regions observed with CHAMP |
title_short |
Thermospheric density structures over the polar regions observed with CHAMP |
title_full |
Thermospheric density structures over the polar regions observed with CHAMP |
title_fullStr |
Thermospheric density structures over the polar regions observed with CHAMP |
title_full_unstemmed |
Thermospheric density structures over the polar regions observed with CHAMP |
title_sort |
thermospheric density structures over the polar regions observed with champ |
publisher |
Copernicus Publications |
series |
Annales Geophysicae |
issn |
0992-7689 1432-0576 |
publishDate |
2005-07-01 |
description |
We report on the unexpected detection of considerable structure in high
latitude thermospheric densities, as derived from an accelerometer onboard
the CHAMP satellite. The width of the structures, which can either be maxima
or minima, varies between a few hundred km and 2000 km. The amplitudes of
these density extrema can reach 50% of ambient. Maxima cluster around
75° (N and S), while minima are found closer to the poles. In a magnetic
latitude-magnetic local time frame the maxima are found mainly around the
cusp region. Overall, the observed structures somewhat resemble so-called
density cells previously found in model calculations. However the models
generate their cells around 140–300 km altitude and show little, if any
remnant at 400 km or above. This has to be contrasted with the fact that the
CHAMP observations were obtained near 430 km altitude. We have explored
Joule heating as a possible mechanism for the generation of the structures,
at least in density enhancement regions, using Hall currents measured on
CHAMP and simultaneous incoherent scatter measurements with EISCAT. However,
the electric fields were usually quite small during the period of
observation, making the quest for an explanation for the structures all the
more challenging.<br><br>
<b>Keywords.</b> Meteorology and atmospheric dynamics (Thermospheric
dynamics) – Magnetospheric physics (Polar cap
phenomena) – Atmospheric composition and structure (Pressure,
density, and temperature) |
url |
https://www.ann-geophys.net/23/1659/2005/angeo-23-1659-2005.pdf |
work_keys_str_mv |
AT kschlegel thermosphericdensitystructuresoverthepolarregionsobservedwithchamp AT hluhr thermosphericdensitystructuresoverthepolarregionsobservedwithchamp AT jpstmaurice thermosphericdensitystructuresoverthepolarregionsobservedwithchamp AT gcrowley thermosphericdensitystructuresoverthepolarregionsobservedwithchamp AT chackert thermosphericdensitystructuresoverthepolarregionsobservedwithchamp |
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