September 7 1973 Two-Ribbon Flare

Abstract

The flare images show a compact, nearly cylindrical arcade centered along the filament channel and composed of 4 prominent loops. The loop systems of Fe XII (T_e = 1.7 10⁶K) and Fe XIV (T_e = 2.3 10⁶K) are smaller than, and lie nested within, the arcades of Fe XVI (T_e = 3 10⁶K) and Ca XVII (Te = 5 10⁶K). The loop arcades at different temperatures, as well as different loops within a given arcade, show different expansion rates. These vary from 6 – 8 km s^–1 for Fe XIV shortly after flare maximum to 0.5 – 1 km s^–1 late in the decay phase. For hotter ions, such as Ca XVII, the velocities are approximately constant at 2 – 3 km s^–1 daring the whole of the observations.