scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Small scale magnetic fluctuations in middle and low latitudes as observed by Oersted
satellite and their possible source in the lower atmosphere
Taira Kent 1 , Iyemori Toshihiko 1 , Stauning Peter 2
1 Graduate School of Science, Kyoto University, 2 Danish Meteorological Institute
Large scale lower atmospheric disturbances caused by typhoon, earthquake, volcanic eruption
etc. are supposed to influence the ionosphere. Such ionospheric effects have been detected by
geomagnetic observation on the ground, and the proposed mechanism which generates the
geomagnetic variation is the ionospheric dynamo. In this paper, the global distribution of
geomagnetic field fluctuations in mid- and low-latitude ionosphere observed by the Oersted
satellite is analyzed. The fluctuations having a few nT in amplitude are orthogonal to the
ambient magnetic field suggesting that they are Alfvenic phenomena or artifacts caused by the
attitude problem. The results indicate a hemispheric asymmetry of the small scale magnetic
fluctuations at the Oersted altitudes, i.e., they are larger in the northern hemisphere than those
in the southern hemisphere. A tendency that the amplitude is larger over the North American
and Eurasian continents suggests the lower atmospheric effects. That is, the ionospheric wind
caused by the acoustic mode and/or gravity mode waves could generate such Alfvenic
fluctuations through the ionospheric dynamo.