hide
Free keywords:
Astrophysics, Solar and Stellar Astrophysics, astro-ph.SR
Abstract:
We use Interface Region Imaging Spectrograph (IRIS) spacecraft data to study
a group of Chromospheric ultraviolet bursts (UVBs) associated with an active
region. We classify the UVBs into two types: smaller ones that can only be
measured once by the scanning slit, and larger UVBs that are measured twice by
the slit. The UVBs' optically thin Si IV 1402.77 \r{A} line profiles are
studied intensively. By fitting the smaller UVBs' lines with 1-2 Gaussians, we
obtain a variety of line-of-sight flow measurements that hint various 3-D
orientations of small scale magnetic reconnections, each associated with a UVB.
The larger UVBs are, however, unique in a way that they each have two sets of
measurements at two slit locations. This makes it possible to unambiguously
detect two oppositely directed heated flows jetting out of a single UVB, a
signature of magnetic reconnection operating at the heart of the UVB. Here we
report on the first of such an observation. Additionally, all the optically
thin Si IV 1402.77 \r{A} line profiles from those UVBs consistently demonstrate
excessive broadening, an order of magnitude larger than would be expected from
thermal broadening, suggesting that those small scale reconnections could be
driven by large scale (macro-scale) turbulence in the active region.
