Quantifying Turbulent Dynamics Found within the Plasma Sheets of Multiple Solar Flares

Abstract

It is vital to our understanding of solar flares that we discern how turbulent motion can affect the magnetic reconnection process. The objective of this study is to quantify the velocity and vorticity structures inherent in the observed motions found in a plasma sheet above arcades during a solar flare. The most noticeable features in these plasma sheets are the supra-arcade downflows (SADs) that sporadically enter the field of view. This work is also attempting to ascertain what effect these SADs have on the flow of plasma at different length scales. Contrast-enhanced images from five flares observed with the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) and Transition Region and Coronal Explorer (TRACE) were used to construct velocity maps—in the plane of the sky—via a Fourier local correlation tracking program. Power-law indices (α) were calculated from the power spectral densities (PSDs) associated with the intensity, kinetic energy, and enstrophy structures of these plasma sheets. Velocity oscillations are observed to be approximately three times stronger for velocities that are perpendicular (V _ϕ ) instead of parallel (V _ρ ) to the magnetic field’s direction. Four of the flares observed were used for producing the following plasma sheet properties: kinetic energy PSD indices with only V _ρ were -0.15 ≤ α _ρ ≤ 0.08, kinetic energy PSD indices with only V _ϕ were -1.59 ≤ α _ϕ ≤ -1.46, kinetic energy PSD indices with both velocities were -0.89 ≤ α ≤ -0.83, enstrophy PSD indices were 0.87 ≤ α ≤ 0.97, kinetic energy density was 16.6 km² s^-2 ≤ ɛ ≤ 60.0 km² s^-2, and enstrophy density was 1.2 × 10^-6 s^-2 ≤ ω ≤ 2.8 × 10^-6 s^-2.