Issue |
A&A
Volume 370, Number 3, May II 2001
|
|
---|---|---|
Page(s) | L41 - L44 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361:20010332 | |
Published online | 15 May 2001 |
Sawtooth oscillations in solar flare radio emission
Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
Corresponding author: A. Klassen, aklassen@aip.de
Received:
29
January
2001
Accepted:
7
March
2001
For the first time, we found a spectral fine structure of solar meter wave
radio burst emission which can be due to sawtooth oscillations in the hot
flare plasma. This finding newly underlines an analogy between coronal and
laboratory plasma processes. The sawteeth occur during
the impulsive flare phase hard X-ray emission and consist of a
sequence of almost identical narrow band ( 1% ) drift
bursts. All cases of our
sample were associated with a radio emitting coronal shock wave
(type II burst). Similar oscillations are familiar in tokamak plasmas
and understood as signature of the kink instability of the toroidal current.
We argue that the radio sawteeth are nonthermal plasma emission due to 2-4%
density fluctuations of the flare plasma. The fluctuations can be excited
by a current instability in a coronal flare loop or in a vertical flaring
current sheet e.g. occuring behind a rising magnetic flux rope. This is
in analogy to kink instability effects observed in laboratory plasmas.
Key words: Sun: flares / radio radiation / corona / plasmas
© ESO, 2001
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