ULF wave interaction with the ionosphere: radar and magnetometer observations

Thursday, 4 September 2014
Regency Ballroom (Hyatt Regency)
Viacheslav Pilipenko1, Evgeniy Fedorov1, Vladimir Borisovich Belakhovsky2, Pavel N. Mager3, Oleg Berngardt3, Mariko Teramoto4 and Timothy K Yeoman5, (1)Institute of Physics of the Earth, Moscow, Russia, (2)Polar Geophysical Institute, Apatity, Russia, (3)Institute of Solar-Terrestrial Physics, Irkutsk, Russia, (4)STE Lab. Nagoya Univ., Sagamihara,Kanagawa, Japan, (5)Univ Leicester, Leicester, United Kingdom
Abstract:
Combined usage of radars and magnetometers, supported by an adequate theory of ULF wave interaction with the multi-layer magnetosphere - ionosphere - atmosphere ground system, is an effective way to reveal the physical mechanism of ULF disturbances. we analyze the data from such combined observations:

- EISCAT radar (the Tromso-Kiruna-Sodankyla system) and IMAGE magnetometers;

- SuperDARN Hokkaido radar and NIICT magnetometers at Kamchatka;

- recently installed SuperDARN radar at Ekaterinburg (Russia) and AANI magnetometers at Arctic shore;

To determine relative contributions of different MHD modes into their structure, the method of apparent impedance can be applied. An approximate analytical relationship derived from the theory of ULF wave transmission through the thin ionosphere has been compared with the measured ratio between the simultaneous ionospheric electric and ground magnetic fields. The impedances of Alfven and compressional modes are predicted to be essentially distinct. This technique has been applied to the interpretation of the following ULF wave events:

- global Pc5 waves at the recovery phase of strong magnetic storm;

- mid-latitude Pi2 pulsations;

- poloidally-polarized Pc5 waves.

From these observations we conclude that global Pc5 pulsations above the ionosphere are predominantly composed from Alfven waves with a small contribution of the fast compressional mode. Observations of mid-latitude Pi2 pulsations showed that the concept of a pure cavity mode is not sufficient to explain these observations, and that a contribution of Alfvén waves must be taken into account. Coordinated high-sampling radar and magnetometer observations are very promising for the examination of the ULF wave structure in the upper ionosphere.

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