Thermal‐Spatial Analysis of Medium and Large Solar Flares, 1976 to 1996

Abstract

Approximately 1100 moderate to large solar flares observed in soft X-rays by the GOES spacecraft, operating between 1976 and 1996, are analyzed individually for thermal and spatial structure by a model that utilizes discrete X-ray measurements, the ensemble X-ray light curve, and scaling laws relating certain thermal properties to spatial dimension. This method endeavors to reproduce a flare's thermal structure in terms of its loop geometry from spatially unresolved measurements, invoking a theoretically conceived and empirically confirmed relationship between the loop scale and temporal behavior of flares. Used in conjunction with a well-known, quasi-static equilibrium scaling law relating loop scale to key thermal parameters, a comprehensive solution of global thermal structure can be closed in the context of this model. The essential characteristics of this model were described by Garcia in an earlier paper showing the step by step procedure for computing the length, cross section, volume, density, mass, and thermal energy of an individual flare loop. The primary purpose of the present work is to utilize the model and method presented by Garcia, based on a small group of flares, to study a much larger sample of flares in order to determine their average characteristics of the above parameters over an extended range of X-ray intensity and size. The ability to utilize spatially unresolved X-ray data to analyze the structure of individual flares at small cost opens the possibility of investigating the average behavior of large populations of X-ray flares, exploiting the largely untapped reservoir of data accumulated since the advent of operational geosynchronous weather satellites.