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In this paper, we describe results of a Solar Maximum Mission (SMM) guest investigation to determine vertical gradients of sunspot magnetic fields for the first time from coordinated observations of photospheric and transition-region fields. Both the photospheric vector field of a sunspot, derived from observations using the NASA Marshall Space Flight Center vector magnetograph, and the line-of-sight component in the transition region, obtained from the SMM Ultraviolet Spectrometer and Polarimeter instrument, are described. From these data, vertical gradients of the line-of-sight magnetic field component are calculated using three methods. (1)The vertical gradient is derived directly from the observations assuming a height difference of 2000 km between the photosphere and transition region. (2)Using the observed transverse photospheric field, the initial gradient (ABz/Az)z = o, is calculated from the condition V. B = 0. (3) Using the photospheric line-of-sight component as the boundary condition in a potential-field calculation, the extrapolated potential field at different heights is compared to the observed transition-region field; from these comparisons, an average height difference is derived and used to calculate the average vertical gradient (ABz/Az). Comparisons of gradients derived from these three methods show consistent results for methods (2) and (3). Deviations of the calculated potential transverse field at z = 0 from the observed transverse component are investigated to assess the validity of gradient calculations using method (3). Since the field is shown to be very close to a potential distribution, we conclude that the vertical gradient ofB z is lower than values from previous studies and the transition-region field occurs at a height of ~ 4000-6000 km above the photosphere.

Abstract. A method is described which uses the NASA-Marshall Space Flight Center (MSFC) Image Data Processing System (IDAPS), MSFC magnetograph data, and X-ray as well as I-Ia observations from the Skylab mission. Solutions of Laplace's equation in three dimensions, based on the magnetograph data, are convolved with observed X-ray and Ha regions. Matched filtering (template matching) provides a best fit of the observed X-ray regions to the computed total magnetic vector magnitude between 10 000 and 15 000 km above the photosphere.

We present a broad range of complementary observations of the onset and impulsive phase of a fairly large (1 B, M 1.2) but simple two-ribbon flare. The observations consist of hard X-ray flux measured by the SMM HXRB S, high-sensitivity measurements of microwave flux at 22 GHz from Itapetinga Radio Observatory, sequences of spectroheliograms in UV emission lines from Ov (T~ 2 x 105 K) and FexxI (T~ 1 • 107 K) from the SMM UVSP, Hot and HeID 3 cine-filtergrams from Big Bear Solar Observatory, and a magnetogram of the flare region from the MSFC Solar Observatory. From these data we conclude:(1) The overall magnetic field configuration in which the flare occurred was a fairly simple, closed arch containing nonpotential substructure.(2) The flare occurred spontaneously within the arch; it was not triggered by emerging magnetic flux.(3) The impulsive energy release occurred in two major spikes. The second spike took place within the flare arch heated in the first spike, but was concentrated on a different subset of field lines. The ratio of Ov emission to hard X-ray emission decreased by at least a factor of 2 from the first spike to the second, probably because the plasma density in the flare arch had increased by chromospheric evaporation.(4) The impulsive energy release most likely occurred in the upper part of the arch; it had three immediate products:(a) An increase in the plasma pressure throughout the flare arch of at least a factor of 10. This is required because the Fe xxI emission was confined to the feet of the flare arch for at least the first minute of the impulsive phase.(b) Nonthermal energetic (~25 keV) electrons which impacted the feet of the arch to produce the hard X-ray burst and impulsive brightening in Ov and D 3. The evidence for this is the simultaneity, within + 2 s, of the peak O v and hard X-ray emissions.(c) Another population of high-energy (~ 100 keV) electrons (decoupled from the population that produced the hard X-rays) that produced the impulsive microwave emission at 22 GHz. This conclusion is drawn because the microwave peak was 6 + 3 s later than the hard X-ray peak.