Ann. Geophysicae 18, 1623±1629�2001) Ó EGS ± Springer-Verlag 2001 The e€ect of magnetic substorms on near-ground atmospheric current
Abstract. Ionosphere-magnetosphere disturbances at high latitudes, e.g. magnetic substorms, are accompanied by energetic particle precipitation and strong variations of the ionospheric electric ®elds and currents. These might reasonably be expected to modify the local atmospheric electric circuit. W...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.371.7455 http://hal.archives-ouvertes.fr/docs/00/31/68/32/PDF/angeo-18-1623-2000.pdf |
| Summary: | Abstract. Ionosphere-magnetosphere disturbances at high latitudes, e.g. magnetic substorms, are accompanied by energetic particle precipitation and strong variations of the ionospheric electric ®elds and currents. These might reasonably be expected to modify the local atmospheric electric circuit. We have analysed air±earth vertical currents �AECs) measured by a long wire antenna at Esrange, northern Sweden during 35 geomagnetic substorms. Using superposed epoch analysis we compare the air-earth current variations during the 3 h before and after the time of the magnetic X-component minimum with those for corresponding local times on 35 days without substorms. After elimination of the average daily variation we can conclude that the e€ect of substorms on AEC is small but distinguishable. It is speculated that the AEC increases observed during about 2 h prior to the geomagnetic X-component minimum, are due to enhancement of the ionospheric electric ®eld. During the subsequent 2 h of the substorm recovery phase, the di€erence between ``substorm' ' and ``quiet' ' atmospheric currents decreases. The amplitude of this ``substorm' ' variation of AEC is estimated to be less than 50 % of the amplitude of the diurnal variation in AEC during the same time interval. The statistical signi®cance of this result was con®rmed using the Van der Waerden X-test. This method was further used to show that the average air-earth current and its ¯uctuations increase during late expansion and early recovery phases of substorms. Key words: Ionosphere �electric ®elds and currents) ± Magnetospheric physics �storms and substorms) ± Meteorology and atmospheric dynamics �atmospheric electricity) |
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