Structure and dynamics of a solar flare - X-ray and XUV observations

Results are presented for an analysis of X-ray and XUV emission from the solar flare that occurred on September 5, 1973. X-ray emission was monitored by ionization chambers aboard the Solrad 9 satellite, and the XUV emission in the wavelength range 170-345 A was recorded by a slitless objective-grating spectroheliograph on Skylab. The physical parameters of the flare plasma, including temperature, density, volume, and magnetic-field configuration, are evaluated. A geometrical loop model is used to determine the volumes of the various emitting regions. The structure of the flare in the rise and decay phases is examined in detail, and conclusions about the effect of various dynamic processes in the flare plasma are made. A major finding is that continued energy release is required well into the flare decay phase. In the rise phase, energy is apparently released only along a small portion of a loop, and in the decay phase apparently throughout most of its length.