Accession Number : ADA137163

Title :   A Study of Coronal Precursors of Solar Flares.

Descriptive Note : Final rept. 26 Jan 82-25 Jul 83,

Corporate Author : AMERICAN SCIENCE AND ENGINEERING INC ARLINGTON MA SPACE SYSTEMS DIV

Personal Author(s) : Webb,D F

PDF Url : ADA137163

Report Date : Aug 1983

Pagination or Media Count : 49

Abstract : This contract was to investigate the evidence for the characteristics of solar coronal flare precursors using high spatial resolution Skylab soft X-ray, H-alpha and magnetogram images. Transient preflare features were examined to develop an understanding of coronal flare precursors, especially what they tell us about changes in the local magnetic field. The results are as follows; Preflare X-ray enhancements were found in a statistically significant number of the preflare intervals searched, and consisted of one to three loops, kernels or sinuous features per interval. Typically, the preflare feature was not at the flare site and did not reach flare brightness. There was no systematically observed time within the preflare interval for the preflare events to appear, and, no correlation of preflare characteristics with the subsequent flare energy. Pressures of several preflare features were calculated to be on the order of a few dy/sq cm. H-alpha brightenings in the form of Knots and patches cospatial with or adjacent to the X-ray preflare features were found in nearly all of the intervals searched. Changing H-alpha absorption features were observed in about half of the cases, and took the form of surges or filament activations. The results do not provide support for loop preheating models, but do support models which require emerging flux as a means of activating larger coronal structures which flare. (Author)

Descriptors :   *SOLAR CORONA, *SOLAR FLARES, X RAYS, BRIGHTNESS, GEOMAGNETISM

Subject Categories : Astrophysics

Distribution Statement : APPROVED FOR PUBLIC RELEASE