Geomagnetic, ionospheric and cosmic ray variations around the passages of different magnetic clouds
Abstract
Thirty-four interplanetary magnetic clouds have been divided into two groups on the basis of Wilson's ( J. geophys. Res.95, 215, 1990) classification: NS clouds (whose Bz near cloud onset at Earth is directed northward, and soon after Bz is turning southward) and SN clouds (those with an opposite behaviour with respect to Bz). Using the days of cloud onsets as key days, geomagnetic, ionospheric and cosmic ray data have been analysed by the superposed epoch analysis method for passages of both NS and SN clouds. On the basis of the daily ∑ Kp values, geomagnetic activity is found to suddenly increase in the vicinity of both types of cloud passages. Afterwards, the variation shown by the geomagnetic indices is found to differ for NS clouds in comparison with SN clouds. Namely, on average the recovery to a normal activity level is much slower for NS clouds. Similarly, the enhancements in the ionospheric absorption of radio waves (the so-called "after-effects") are found to show different signatures according to cloud type, an interpretation also valid for variations in cosmic ray intensity. The latter results are based on analyses of neutron monitor counts observed at two stations (Apatity: 67°N; and Moscow: 55°N).
- Publication:
-
Planetary and Space Science
- Pub Date:
- July 1992
- DOI:
- 10.1016/0032-0633(92)90138-E
- Bibcode:
- 1992P&SS...40..979M
- Keywords:
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- Cosmic Rays;
- Interplanetary Space;
- Ionospheric Disturbances;
- Magnetic Clouds;
- Magnetic Variations;
- Interplanetary Magnetic Fields;
- Magnetic Field Configurations;
- Geophysics