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Geomagnetic Effects of X-flare 4.11.2003
Parkhomov V.A, Parkhomov V.A,
Parkhomov V.A. , Moldavanov A.V.
1. Baikal State University of Economy and Law, Irkutsk, Russia
2. Tranzeo Wireless Technologies, Inc., Vancuver, Canada
These days ionospheric processes caused by electromagnetic radiation of solar flares are studied well enough. However, during enormous X-flare on 4.11.2003 (GOES rate X18+) some geomagnetic effects has been registered that were not observed before.
For experimental analysis of data from daytime stations were used the riometer (Canopus) and magnetometer (Canopus and Intermagnet) networks.
Investigation showed that during the drastic (up to two orders of magnitude) growing of hard (12-50 KeV) X-rays flux at geostationary orbit (spacecraft 'Hessi') there was synchronous significant rise of space noises absorption from middle latitudes to polar cap range and geomagnetic pulsations generation with periods 15-550 s (Psfe).
Spatially-temporal features of spectral and amplitude characteristics of geomagnetic pulsations Psfe and their relation to variations of flare X- and gamma radiation are considered. Peak amplitude (~ 100 nT at latitude ~ 67 N near noon) of observed pulsations with period ~ 550 s occurred at 20.20-20.45 UT after ending of optical phase of flare. Similar oscillatory form (peak amplitude ~ 10 nT in Bz-component of geomagnetic field) was also happening at this time on geostationary orbit (GOES-10 records). Time interval of increasing of pulsations amplitude coincided with strong (up to two orders of magnitude) escalating of hard X- and gamma rays flux in energy band 25-800 KeV. At this time the flux attenuation in neighbor spectral bands (3-25 KeV) and (800-20000 KeV) also occurred.
Possible mechanisms of pulsations originating for different spectral bands are considered. At low frequency end (Pc5 range), the pulsations arising can be related to generation of Alfven waves at quick increasing of the ionosphere conductivity. We argue this suggestion by features of Psfe polarization in conjugate magnetic observatories and on satellite GOES-10.
In periods range 15 - 150 s, two models of pulsations appearance are discussed: directly driven model and storage-release one. Both these models exploit the fact of jumping of flux in band 25 - 800 KeV. Taking into account the real stratification of the Earth atmosphere in regards to incident radiation energy, authors come to conclusion that potential source of observing pulsations should be positioned on sub-ionosphereic altitudes (< 70 km).