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Chertok I.M. Fomichev V.V. Gnezdilov A.A. Gorgutsa R.V. Grechnev V.V. Markeev A.K. Nightingale R.W. Sobolev D.E. 《Solar physics》2001,204(1-2):139-152
The 14 July 2000 (`Bastille Day') eruptive and geoeffective flare event was observed by the digital IZMIRAN radio spectrograph
in the frequency range of 25–270 MHz. This instrument allowed the analysis of various features of the dynamic radio spectrum
and their comparison with other observational data, in particular with development of a spectacular EUV post-eruption arcade
recorded aboard the Transition Region and Coronal Explorer (TRACE). (1) A compressed multi-hour radio spectrum shows that
the event caused a conspicuous weakening of the pre-existing noise storm. This phenomenon was perhaps caused by interaction
of a large halo coronal mass ejection (CME), recorded by the the Large Angle and Spectroscopic Coronagraph (LASCO) aboard
the Solar and Heliospheric Observatory (SOHO), with emitting coronal structures. (2) Several type II bands are present at
the initial and maximum phases of the flare event. The frequency drifts of the clearest bands correspond to the estimated
shock wave speed of 1100–2300 km s−1 that is comparable with the CME speed observed in the sky plane. (3) Significant broadband enhancements of the metric radio
emission took place around of 10:24–10:27 UT coinciding with sharp development of the EUV arcade in the northeast direction.
It appears to correspond to the intensification of the electron acceleration in a process of post-eruption loop formation.
(4) The high-resolution radio spectrum revealed a superposition of numerous type III-like bursts and/or pulsations with a
time scale ranging from a few seconds to several tens of seconds. These features can be attributed particularly to successive
formation of new loops of the arcade and corresponding temporal fragmentation of the electron acceleration in the course of
the post-eruption reconnection. In summary, the analysis demonstrates the correspondence between the multi-scale temporal
features of the metric radio emission and such phenomena as the CME and post-eruption EUV arcade. Some spectra, images, and
movies illustrating the event are presented also on the accompanying CD-ROM.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1014224004946 相似文献
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We discuss a little-known variety of sharp decreases of long-duration meter-wavelength noise storms and type IV bursts. A survey of the IZMIRAN and AIP radio observations shows that a decrease or nearly complete disappearance of the continuum and bursts developing over tens of minutes without a subsequent recovery of the radio flux occasionally occurs. The decrease is usually preceded by a short-duration (several tens of minutes) enhancement of the radio emission. In these events, the onset of the flux decrease drifts from high to low frequencies with a rate of –(0.05–0.35) MHz s–1, comparable to the drift rates of noise-storm onsets and of chains of type I bursts. White-light coronagraph observations, as well as the characteristics of the accompanying microwave and soft X-ray emissions, provide evidence that such radio decreases appear to be associated with coronal mass ejections (CMEs) and post-CME phenomena. Yohkoh/SXT images show radio flux decrease events which are accompanied by significant rearrangements of coronal structures. We suggest that the radio flux variations are caused by CME interactions with pre-existing coronal arcade structures which are sources of noise storms and energetic electron acceleration. The fact that the noise-storm decreases develop with delays of several tens of minutes relative to the associated microwave burst peak, when the corresponding CME front is located at heights of several R
, however, is not explained. 相似文献
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