Coronal Heating Events in High-Cadence Trace Data

Abstract

On March 23rd 1999 a set of TRACE (Transition Region and Coronal Explorer) observations were taken in support of Solar and Heliospheric Observatory (SOHO) / TRACE Joint Observing Program 83. The program is designed to look for coronal heating mechanisms operating at high cadence and to observe their dynamical effects on coronal loop density, temperature and magnetic structure. We present here a study of 27 small, dynamic brightening events seen in this data. These events are seen in the quiet-Sun areas surrounding the active region. The data itself consists of 157 171 A 512×512 arc sec images at 1 arc sec resolution and 9 second cadence, a previously unavailable combination of cadence, resolution and image size. Three classes of events are introduced: complex, intermediate and simple. All three classes share the property of being dynamic on small time and length scales but differ in the complexity of their behavior. We find that the brightenings across all classes exhibit variations as part of a distribution of time scales (90–400 s) peaked around 228 s. The brightenings are no more than 5 arc sec in diameter. Motions between brightenings occur on time scales from 9 to 90 s and on length scales no greater than 10 arc sec. These motions have velocities estimated to be in the range 89–174 km s−1. The position of these events in the spectrum of previously observed coronal heating events is discussed.