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  • 1 Geodetic and Geophysical Research Institute of the Hungarian Academy of Sciences POB 5 H-9401 Sopron Hungary
  • | 2 Eötvös Loránd Geophysical Institute of Hungary Tihany Observatory, Department of Earth Physics Tihany Hungary
  • | 3 GeoForschungsZentrum Potsdam, Telegrafenberg D-14473 Potsdam Germany
  • | 4 Kyushu University 33 Department of Earth and Planetary Sciences 6-10-1 Hakozaki Fukuoka 812-8581 Japan
  • | 5 International Arctic Environment Research Project Group National Institute of Information and Communications Technology 4-2-1 Nukui-kita, Koganei Tokyo 184-8795 Japan
  • | 6 Academy of Sciences of the Czech Republic Geophysical Institute Boční II/1401 141 31 Praha 4 Czech Republic
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The total solar eclipse of August 11, 1999 offered a unique opportunity for the study of its geomagnetic effect — more specifically, of its effect on geomagnetic (Pc3) pulsations, as it swept through Europes many observatories, and additional temporary stations have also been established by Japanese, German and Hungarian groups. The present paper starts with an analysis of the ionospheric-interplanetary background. In the interplanetary medium, no indication was found which could result in any extraordinary event in pulsation activity. The both horizontally and vertically widespread ionospheric effect (electron density decrease) explains a change of the polarisation angle by about ten degrees in the local field line resonance (FLR) band. However, the most significant solar eclipse effect was identified as dramatic clockwise rotation (up to 70 degrees) of the polarisation ellipse of Pc3, Pc4 and Pc5 pulsations. Pulsation data exhibit a strong amplitude decrease (roughly by a factor of two) in and around the totality spot of the eclipse. The decrease is most significant at the local field line resonance (FLR) period. In the actual case, the FLR decrease swept over Europe with a speed being similar to the speed of the dark spot. We suppose that the FLR mechanism was disturbed by the change of particle distribution along the field lines ending in the dark zone due to upward propagation of the electron density decrease caused by the lack of ionising solar radiation in the E-layer of the ionosphere. Thus, the FLR mechanism can be disturbed both from outside, by a sudden change of the interplanetary magnetic field (Verő et al. 1998) and from inside, by a change of the particle density/distribution along the actual field line.

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Acta Geodaetica et Geophysica
Language English
Size B5
Year of
Foundation
2013
Volumes
per Year
1
Issues
per Year
4
Founder Magyar Tudományos Akadémia
Founder's
Address
H-1051 Budapest, Hungary, Széchenyi István tér 9.
Publisher Akadémiai Kiadó Springer
Nature Switzerland AG
Publisher's
Address
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
CH-6330 Cham, Switzerland Gewerbestrasse 11.
Responsible
Publisher
Chief Executive Officer, Akadémiai Kiadó
ISSN 2213-5812 (Print)
ISSN 2213-5820 (Online)

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