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Abstract
Experimental results from HF pumping experiments in the nightside auroral E and F region are reported. The experiments were carried out by the use of
the EISCAT HF heating facility located near Tromsø, Norway, allowing HF pumping the ionosphere in a near magnetic field-aligned direction. We present
experimental results from multi-instrument observations related to heater-induced phenomena in a coupled ionosphere–magnetosphere system. The
following results have been observed on different occasions: a reverberation effect in scattered signals observed simultaneously on two diagnostic
paths which is an indication of Alfvén wave generation. This phenomenon was seen under specific disturbed background geophysical conditions, namely,
a high electron density in the F region up to 8 MHz produced by soft electron precipitation from the magnetosphere along with low electron density in
lower ionosphere; increased ionospheric electric fields; ion outflows from the ionosphere. On another occasion a magnetospheric response to heater
turning on and off was found from magnetic pulsation observations over a frequency range up to 5 Hz (the upper frequency limit of the sensitive
magnetometer at Kilpisjarvi, located near Tromsø). The response manifests itself about 1 min after the heater is turned on and off. Other results
have shown the modification of a natural auroral arc and local spiral-like formation. It is thought that a local heater-driven current system is
formed. An interesting feature is the generation of the heater-induced ion outflows from the ionosphere. They are observed in night hours under both
quiet and disturbed magnetic conditions.
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[edit on 19-2-2010 by Romans 10:9]


