Multi-wavelength observations of the 1998 September 27 flare spray |
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| Authors: | Gallagher Peter T Williams David R Phillips Kenneth JH Mathioudakis Mihalis Smartt Raymond N Keenan Francis P |
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| Institution: | (1) Department of Pure and Applied Physics, The Queen's University of Belfast, Belfast, , BT7 1NN, , N. Ireland, U.K;(2) Space Science and Technology Department, Rutherford Appleton Laboratory, Chilton, Didcot, , Oxon. , OX11 0QX, , U.K;(3) National Solar Observatory, Sacramento Peak, Sunspot, NM, 88349, U.S.A. |
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| Abstract: | We report on observations of a large eruptive event associated with a flare that occurred on 27 September 1998 made with the Richard B. Dunn Solar Telescope at Sacramento Peak Observatory (several wave bands including off-line-center H ), in soft and hard X-rays (GOES and BATSE), and in several TRACE wave bands (including Fe ix/x 171 Å, Fexii 195 Å, and Civ 1550 Å). The flare initiation is signaled by two H foot-point brightenings which are closely followed by a hard X-ray burst and a subsequent gradual increase in other wavelengths. The flare light curves show a complicated, three-component structure which includes two minor maxima before the main GOES class C5.2 peak after which there is a characteristic exponential decline. During the initial stages, a large spray event is observed within seconds of the hard X-ray burst which can be directly associated with a two-ribbon flare in H. The emission returns to pre-flare levels after about 35 min, by which time a set of bright post-flare loops have begun to form at temperatures of about 1.0–1.5 MK. Part of the flare plasma also intrudes into the penumbra of a large sunspot, generally a characteristic of very powerful flares, but the flare importance in GOES soft X-rays is in fact relatively modest. Much of the energy appears to be in the form of a second ejection which is observed in optical and ultraviolet bands, traveling out via several magnetic flux tubes from the main flare site (about 60° from Sun center) to beyond the limb. |
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