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M. Swisdak

Publications and source records attributed to M. Swisdak.

12 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

Direct Observation of Electron Temperature Anisotropy Localized to One Separatrix during Electron-Only Magnetic Reconnection in a Laboratory Plasma

Anisotropic electron heating, Te∥/Te⊥ > 1 (relative to the local magnetic field) during electron-only magnetic reconnection with a large guide field is directly measured in a laboratory plasma through multi-dimensional incoherent Thomson scattering measurements of the electron velocity distribution function. The preferentially parallel electron heating is localized to one separatrix in the reconnection plane and anisotropies of 1.5 are observed. The localization of the heating to one separatrix and the anisotropy are reproduced with a 2D particle-in-cell simulation. The characteristics of the anisotropic heating are consistent with predictions for electron energization by the parallel reconnection electric field under strong guide field. The effective electron temperature is found to increase throughout the outflow region, a possible indication of the effects of collisions and the fully 3D nature of magnetic reconnection in the experiment.

Peiyun Shi↗
NASA NTRS2022

Correlated Spatio-temporal Evolution of Extreme-Ultraviolet Ribbons and Hard X-Rays in a Solar Flare

We analyze the structure and evolution of ribbons from the M7.3 SOL2014-04-18T13 flare using ultraviolet images from the Interface Region Imaging Spectrograph and the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA), magnetic data from the SDO/Helioseismic and Magnetic Imager, hard X-ray (HXR) images from the Reuven Ramaty High Energy Solar Spectroscopic Imager, and light curves from the Fermi/Gamma-ray Burst Monitor, in order to infer properties of coronal magnetic reconnection. As the event progresses, two flare ribbons spread away from the magnetic polarity inversion line. The width of the newly brightened front along the extension of the ribbon is highly intermittent in both space and time, presumably reflecting nonuniformities in the structure and/or dynamics of the flare current sheet. Furthermore, the ribbon width grows most rapidly in regions exhibiting concentrated nonthermal HXR emission, with sharp increases slightly preceding the HXR bursts. The light curve of the ultraviolet emission matches the HXR light curve at photon energies above 25 keV. In other regions the ribbon-width evolution and light curves do not temporally correlate with the HXR emission. This indicates that the production of nonthermal electrons is highly nonuniform within the flare current sheet. Our results suggest a strong connection between the production of nonthermal electrons and the locally enhanced perpendicular extent of flare ribbon fronts, which in turn reflects the inhomogeneous structure and/or reconnection dynamics of the current sheet. Despite this variability, the ribbon fronts remain nearly continuous, quasi-one-dimensional features. Thus, although the reconnecting coronal current sheets are highly structured, they remain quasi-two-dimensional and the magnetic energy release occurs systematically, rather than stochastically, through the volume of the reconnecting magnetic flux.

S. J. Naus↗