Paper#: 3
Poster #:
Session Name: Workshop 6A: Ionospheric Process
Room: 200ABC
Day: Thursday
Time: 2:40-3:00 p.m.
Abstract Title: Modification of the Ionosphere- Magnetosphere Coupling by HF Pumping into Night-Side Auroral Ionosphere
PresentSurname: Blagoveshchenskaya, N.
All Authors: N. Blagoveshchenskaya , V.A. Kornienko, M.T. Rietveld, B. Thide', M.J. Kosch
Abstract : Experimental results from Tromso HF pumping experiments in the nightside auroral ionosphere are reported. Experiments were conducted by using the EISCAT HF heating facility located near Tromso. A bistatic HF Doppler radio scattering setup has been used in conjunction with the EISCAT UHF radar, the DASI digital all-sky imager, the IMAGE magnetometer network, to find the evidence that powerful HF radio waves beamed in the field-aligned direction produce the modification of the ionosphere-magnetosphere coupling which can lead to the auroral activations. Summarizing multi-instrument observations one can distinguish the following peculiarities related to these activations: modification of the auroral arc and its break-up above Tromso; local changes of currents and horizontal electric fields; strong increases (in 2-3 times) of the electron and ion temperatures in a wide altitude range from 200 to 600 km; the occurrence of the intense upward! ion flows at the heights above 350 km; distinctive features in dynamic HF radio scatter Doppler spectra; auroral activations above Tromso. The possible mechanisms of these activations through the parallel electric field formation, the appearance of the additional low-altitude ( 350-1000 km ) acceleration region, the enhancement of field-aligned currents due to positive feedback instability are discussed. The obtained results prove the active role of the auroral ionosphere in a substorm process and provide a strong evidence that the location and timing of the auroral activation was related to the HF pumping experiments, but its energy source remains the interaction between the solar wind and the magnetosphere.