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| Titel |
Upper-mesospheric temperatures measured during intense substorms in the declining phase of the January 2005 solar proton events |
| VerfasserIn |
H. Nesse Tyssøy, D. Heinrich, J. Stadsnes, M. Sørbø, U.-P. Hoppe, D. S. Evans, B. P. Williams, F. Honary |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 26, no. 9 ; Nr. 26, no. 9 (2008-09-01), S.2515-2529 |
| Datensatznummer |
250016207
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| Publikation (Nr.) |
 copernicus.org/angeo-26-2515-2008.pdf |
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| Zusammenfassung |
Temperature measurements from the ALOMAR Weber Na lidar together with cosmic
radio noise absorption measurements from IRIS and particle measurements from
NOAA 15, 16 and 17 are used to study effects of geomagnetic activity on the
polar winter upper-mesospheric temperature. On 21–22 January 2005 we have 14 h
of continuous temperature measurement with the Na lidar coinciding
with strong geomagnetic activity in the declining phase of one of the
hardest and most energetic Solar Proton Event (SPE) of solar cycle 23.
According to measurements by the imaging riometer IRIS in northern Finland,
the temperature measurements coincide with two periods of increased cosmic
radio noise absorption. Particle measurements from the three satellites,
NOAA 15, 16 and 17 that pass through and near our region of interest confirm
that the absorption events are probably due to particle precipitation and
not due to changes in e.g. the electron recombination coefficient.
The measured temperature variation at 85 and 90 km is dominated by a 7.6-h
wave with downward phase propagation and a vertical wavelength of
approximately 10 km. Assuming that the wave is due to a lower altitude
source independent of the particle precipitation, we do not find any
temperature modification that seems to be related to the absorption events.
The average temperature is larger than expected above 90 km based on MSIS
and the monthly mean from falling spheres, which could be due to particle
precipitation and Joule heating prior to our measurement period. There is
also a possibility that the identified wave phenomenon is an effect of the
geomagnetic activity itself. Earlier studies have reported of similar
wavelike structures in wind observations made by the EISCAT VHF radar during
SPEs, and found it conceivable that the wave could be excited by the effect
of energetic particles precipitating into the mesosphere. |
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