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| Titel |
Statistical analyses on low latitude thermospheric mass density measured by CHAMP in relation to solar and magnetospheric influences |
| VerfasserIn |
S. Müller, H. Lühr, S. Rentz |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250019765
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| Zusammenfassung |
| In our study we have performed statistical analyses on thermospheric mass density data at
equatorial latitudes in order to identify its response to various drivers. It is based on four years
(2002 - 2005) of CHAMP accelerometer measurements.
To isolate the influence of the different contributions we perform a dedicated data selection
and/or removal of other effects. First we normalise all readings to an altitude of 400 km. For
the investigation of the solar influences only magnetically quiet days (Ap < 15) are
considered. The air density exhibits clear annual and semi-annual variations with maxima at
the equinoxes and a pronounced minimum around June solstice. The thermosphere
maintains a day/night density ration very close to 2 during quiet days. This ratio is
independent of solar flux level and season. The magnetospheric forcing causes an additive
contribution to the quiet-time density, which is linearly correlated with the am
index.
Thus we can delineate the influences of the contributions of solar flux level (P10.7-index),
magnetic activity (ap and am indices), local time and seasonal influences. The
forcing terms can be treated as linear combinations of the respective components. |
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