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| Titel |
Diagnostics of solar flare reconnection |
| VerfasserIn |
M. Karlický, M. Bárta |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 11, no. 4 ; Nr. 11, no. 4 (2004-11-01), S.471-483 |
| Datensatznummer |
250009328
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| Publikation (Nr.) |
 copernicus.org/npg-11-471-2004.pdf |
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| Zusammenfassung |
| We present new diagnostics of the solar flare reconnection, mainly based on the
plasma radio emission. We propose that the high-frequency (600-2000 MHz) slowly
drifting pulsating structures map the flare magnetic field reconnection. These
structures correspond to the radio emission from plasmoids which are formed in
the extended current sheet due to tearing and coalescence processes. An
increase of the frequency drift of the drifting structures is interpreted as an
increase of the reconnection rate. Using this model, time scales of slowly
drifting pulsating structure observed during the 12 April 2001 flare by the
Trieste radiopolarimeter with high time resolution (1 ms) are interpreted as a
radio manifestation of electron beams accelerated in the multi-scale
reconnection process. For short periods Fourier spectra of the observed
structure have a power-law form with power-law indices in the 1.3-1.6 range.
For comparison the 2-D MHD numerical modeling of the multi-scale reconnection
is made and it is shown that Fourier spectrum of the reconnection dissipation
power has also a power-law form, but with power-law index 2. Furthermore, we
compute a time evolution of plasma parameters (density, magnetic field etc) in
the 2-D MHD model of the reconnection. Then assuming a plasma radio emission
from locations, where the "double-resonance" instability generates the
upper-hybrid waves due to unstable distribution function of suprathermal
electrons, we model radio spectra. Effects of the MHD turbulence are included.
The resulting spectra are compared with those observed. It is found, that
depending on model parameters the lace bursts and the decimetric spikes can be
reproduced. Thus, it is shown that the model can be used for diagnostics of the
flare reconnection process. We also point out possible radio signatures of
reconnection outflow termination shocks. They are detected as type II-like
herringbone structures in the 200-700 MHz frequency range. Finally, we mention
Hα spectra of the 18 September 1995 eruptive prominence which indicate
the bi-directional plasma flow as expected in the reconnection process. |
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