DISCRETE RANDOM HEATING EVENTS IN CORONAL LOOPS

The response of the coronal plasma in a magnetic loop to the release of discrete, random amounts of energy quanta over fixed time intervals is investigated. Nanoflare heating (10²⁴ erg per event) with event lifetimes on a scale of 1–20 s are shown to be able to maintain a coronal loop at typical coronal temperatures, 2 x 10⁶ K (Parker, 1988; Kopp and Poletto, 1993). Microflare events (10²⁷ erg) observed by Porter et al. (1995) with a lifetime of approximately 1 min are also investigated and it is found that the loop apex temperature varies by at most 40% from its initial static condition. However, larger energy events of the order of 10²⁸ erg (Schmieder et al., 1994) occur too infrequently and the plasma cools to chromospheric values. The implications of time-dependent heating of the corona upon observations are also discussed.