THE MORPHOLOGY OF FLARE PHENOMENA, MAGNETIC-FIELDS, AND ELECTRIC CURRENTS IN ACTIVE REGIONS .1. INTRODUCTION AND METHODS

This paper introduces a study of electric current systems in solar act ive regions and their spatial relationship to sites of electron precip itation and high pressure in flares. The primary purpose of this study is to provide observational evidence for or against the flare models commonly discussed in the literature. We determine the photospheric di stribution of vertical currents from vector magnetograms. We use Halph a line profiles to identify sites of intense nonthermal electron preci pitation into the chromosphere and of high pressure in the overlying c orona. By observing complete Halpha spectra. rather than just narrow-b and images, we are able to distinguish between electron precipitation and high-pressure sites in the observed flares. By measuring the full Stokes profiles, we can eliminate magneto-optical effects and make fir st-order corrections for under-resolution in the analysis. By observin g continuum images with both the magnetograms and the Halpha spectrohe liograms, we are able to achieve coregistration accuracy less-than-or- equal-to 3''. Finally, by eliminating projection effects in the magnet ic data we are able to compute true vertical currents. In this introdu ctory paper we describe the specifics of the instrumentation and data used, which primarily originate from Mees Solar Observatory of the Uni versity of Hawaii, and we describe the data analysis methods. We summa rize several flare models and describe what each predicts for the rela tionships of flares to the vertical current systems. In subsequent pap ers we present observations of flares in particular active regions and interpret the findings in the context of the models discussed in this paper.