High-sensitivity observations of solar flare decimeter radiation |
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Arnold O. Benz Submitted: 2000-12-05 01:40
A new acousto-optic radio spectrometer has observed the 1 - 2 GHz radio emission
of solar flares with unprecedented sensitivity. The number of detected decimeter
type III bursts is greatly enhanced compared to observations by conventional
spectrometers observing only one frequency at the time. The observations
indicate a large number of electron beams propagating in dense plasmas. For the
first time, we report weak, reversed drifting type III bursts at frequencies
above simultaneous narrowband decimeter spikes. The type III bursts are reliable
signatures of electron beams propagating downward in the corona, apparently away
from the source of the spikes. The observations contradict the most popular
spike model that places the spike sources at the footpoints of loops. Conspicuous
also was an apparent bidirectional type U burst forming a fish-like pattern. It
occurs simultaneously with an intense U-burst at 600-370 MHz observed in
Tremsdorf. We suggest that it intermodulated with strong terrestrial interference
(cellular phones) causing a spurious symmetric pattern in the spectrogram at
1.4 GHz. Symmetric features in the 1 - 2 GHz range, some already reported in the
literature, therefore must be considered with utmost caution.
Authors: Arnold O. Benz, Peter Messmer and Christian Monstein
Projects: None
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Publication Status: Astronomy and Astrophysics, 366, 326 - 330 (2001)
Last Modified: 2005-11-21 03:34
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