The morphology of flare phenomena, magnetic fields, and electric currents in active regions. II. NOAA active region 5747 (1989 October)

In this paper we describe the morphology of energetic electron precipitation and high-pressure coronal flare plasmas of three flares relative to the vector magnetic field and vertical electric currents that we observed in NOAA Active Region 5747 in 1989 October. Using Hα imaging spectroscopy, we have identified the chromospheric sites of intense nonthermal electron precipitation and high coronal pressure during these flares. Using the full Stokes profiles of two photospheric Fe I lines (6301.5 and 6302.5 Å), we have derived vector magnetograms fo a period of 5 consecutive days, during which these flares occurred. From these photospheric magnetograms, we have determined the sites of the major vertical currents in this region. We have co-aligned the Hα spectroheliograms with the vector magnetograms using continuum images of sunspots, which enables positional accuracy of a few seconds of arc. We find that during the gradual phase, the regions of the Hα flare that show the effects of enhanced pressure in the overlying corona often encompass extrema of the vertical current density. This is consistent with earlier work showing a close relationship between Hα emission and line-of-sight currents. However the sites of precipitation of nonthermal electrons into the chromosphere lie close to the magnetic neutral line, on the shoulders of vertical current channels, rather than at vertical current maxima. This result is generally inconsistent with earlier works' support of current-interruption models such as that of Alfvén & Carlqvist (1967), except insofar as they apply to nearly horizontal currents. Our data are consistent with the overall morphology and evolution described by erupting-filament models such as those of Kopp & Pneuman (1976) and Sturrock (1989). The possibility that flares accelerate energetic electrons in strong nearly horizontal current channels remains to be investigated.