Statistical analysis of evolving flare parameters inferred from spatially-resolved microwave spectra observed with the Expanded Owens Valley Solar Array

The newly completed Expanded Owens Valley Solar Array (EOVSA) performed microwave (MW) imaging spectroscopy observations during several flares that occurred during the first half of September 2017. The unprecedented high frequency and spatial resolution of these observations allowed us for the first time to infer, with 2-arcsecond spatial resolution and 1-second temporal cadence, the spatial distribution and evolution of the coronal magnetic field strength, the number density of the accelerated electrons, the power-law index of their energy distribution, as well as other associated flare parameters. Our methodology, which consists of independently fitting the MW spectra corresponding to each individual pixel of the evolving mult-frequency maps with uniform gyrosynchrotron source models, generated a statistically significant collection of evolving flare parameters whose generally smooth spatial and time variation demonstrates a collective behavior of the neighboring volume elements, and thus validates our approach. Here we report on the statistical properties of these physical flare parameters, their spatial distributions, and their temporal trends for significant portions of the duration of each flare, and we interpret our results in the context of the standard solar flare model involving magnetic energy release, magnetic reconnection, and particle acceleration.