Low-Altitude Reconnection Inflow-Outflow Observations during a 2010 November 3 Solar Eruption

TL;DR

This study presents detailed observations of inflows and outflows during a 2010 solar eruption, providing insights into magnetic reconnection dynamics through EUV imaging and velocity measurements.

Contribution

First detailed measurement of inflow and outflow speeds during a solar flare, linking EUV observations with reconnection models and plasma acceleration.

Findings

Inflow speeds ranged from ~150-690 km/s, with higher speeds at higher temperatures.

Inflow and outflow events occurred nearly simultaneously with RHESSI thermal peaks.

Outflows showed acceleration, with speeds up to 10^3 km/s, indicating dynamic reconnection processes.

Abstract

For a solar flare occurring on 2010 November 3, we present observations using several SDO/AIA extreme-ultraviolet (EUV) passbands of an erupting flux rope followed by inflows sweeping into a current sheet region. The inflows are soon followed by outflows appearing to originate from near the termination point of the inflowing motion - an observation in line with standard magnetic reconnection models. We measure average inflow plane-of-sky speeds to range from ~150-690 km/s with the initial, high-temperature inflows being the fastest. Using the inflow speeds and a range of Alfven speeds, we estimate the Alfvenic Mach number which appears to decrease with time. We also provide inflow and outflow times with respect to RHESSI count rates and find that the fast, high-temperature inflows occur simultaneously with a peak in the RHESSI thermal lightcurve. Five candidate inflow-outflow pairs are identified with no more than a minute delay between detections. The inflow speeds of these pairs are measured to be 10^2 km/s with outflow speeds ranging from 10^2-10^3 km/s - indicating acceleration during the reconnection process. The fastest of these outflows are in the form of apparently traveling density enhancements along the legs of the loops rather than the loop apexes themselves. These flows could either be accelerated plasma, shocks, or waves prompted by reconnection. The measurements presented here show an order of magnitude difference between the retraction speeds of the loops and the speed of the density enhancements within the loops - presumably exiting the reconnection site.