Astron. Astrophys. 347, 684-695 (1999)

X-ray and radio manifestations of a solar eruptive event

N. Gopalswamy ¹, N. Nitta ², P.K. Manoharan ³, A. Raoult ⁴ and M. Pick <sup>4

1</sup> Department of Physics, The Catholic University of America, Washington DC and NASA/GSFC, Greenbelt, MD 20771, USA
² Lockheed Martin Advanced Technology Center, Building 252, Department H1-12, 3251 Hanover Street, Palo Alto, CA 94304, USA
³ Radio Astronomy Center, TIFR, Ooty, India
⁴ Meudon Observatory, Section A'Astrophysique, 5 Place Jules Janssen, F-92195 Meudon Principal Cedex, Paris, France

Received 17 July 1998 / Accepted 8 April 1999

Abstract

We report on a study of the changes in the vicinity of a disappearing solar filament (DSF) that occurred on 1993 April 30. The DSF was associated with a long duration X-ray event (LDE) observed by the GOES and Yohkoh spacecraft. A detailed analysis of the X-ray images obtained by the Yohkoh Soft X-ray Telescope revealed that X-ray manifestations of the eruption were wide-spread: (i) X-ray enhancement over a coronal volume several times larger than that of the eruption region, probably the X-ray counterpart of a coronal mass ejection (CME), (ii) X-ray ejecta accelerating to 670 km s^-1 into the corona, and (iii) quasi-stationary X-ray loops as in long decay events (LDEs) were observed. One of the important findings of this study is the large-scale X-ray enhancement which we identify with the frontal structure of a CME, apart from the well-known X-ray ejecta and post-eruption arcade formation. There is evidence for triggering of a sympathetic flare in an adjoining active region due to the X-ray ejecta from the eruption region. Stationary metric radio continuum observed by the Nançay Radioheliograph was found to be associated with the brightest X-ray loops that formed following the filament eruption. The unpolarized continuum radio emission was found to be bremsstrahlung radiation from the hot plasma observed in X-rays. The event was also associated with a low frequency metric type II radio burst due to a coronal shock wave from the eruption region. The onset time of the type II emission precludes the possibility of a CME-driven shock causing it. Although we do not have positional information for the type II burst, we found that the X-ray ejecta was fast enough to drive the coronal shock. We confirmed this by comparing the speed of the X-ray ejecta with the shock speed obtained from the radio data which agreed within 10%.

Key words: Sun: corona Sun: filaments Sun: flares Sun: radio radiation Sun: X-rays, gamma rays

Send offprint requests to: N. Gopalswamy

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Contents

• 1. Introduction
• 2. Observational results
  • 2.1. The filament disappearance
  • 2.2. Metric type II burst and radio continuum
  • 2.3. Details of the eruption in soft X-rays
    • 2.3.1. X-ray activity in the DSF region
    • 2.3.2. Large-scale X-ray enhancement: a CME
• 3. Temperature and emission measure analysis
  • 3.1. Temperature and EM for the flare region
• 4. Metric radio emissions
  • 4.1. Coronal shock source for the type II burst
  • 4.2. Continuum radio emission
• 5. Discussion
• 6. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1999

Online publication: June 30, 1999
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