Speaker
Lakshmi Pradeep Chitta
(Max Planck Institute for Solar System Research)
Description
Magnetic reconnection is thought to be responsible for eruptive events on the Sun,
from large-scale CMEs to small-scale events that are barely resolved. The height in
the solar atmosphere where the reconnection takes place may significantly influence
the morphology and appearance of the events. This might be the main distinction
between events such as e.g. Ellerman bombs, IRIS bombs, or explosive events which are
observed in spectral lines forming at different temperatures showing different line
profile characteristics. Here we report a prolonged reconnection event caused by a
magnetic feature moving from a sunspot to an adjacent pore. Data-driven nonlinear
force-free field extrapolations and magneto-frictional models suggest that the strong
dominant sunspot and the pore of the same polarity lead to a canopy-type field
structure at low heights. The moving magnetic feature of the opposite polarity
reconnects with the overlying canopy. The models suggest a height of the reconnection
only about 500 km above tau=1. The IRIS observations of this event show complex Mg
II, C II, and Si IV line profiles, in part similar to those reported earlier for IRIS
bombs. We find evidence for strong spatial, velocity discontinuities from red to
blueshifts in the Si IV Dopplergrams at the reconnection site. Additionally, multiple
blueshifted components along the same line of sight are also observed. Further, there
is evidence that the downflowing plasma from the reconnection site interacts with
chromospheric plasma, increasing the apparent brightness of the structure. The
magnetic modelling of these events supports the earlier suggestions that the location
of the reconnection of these active region UV bursts is very low in the atmosphere,
in the low chromosphere or even in the photosphere. Small-scale events like this may
give insights into the dynamics and complex evolution of large-scale eruptive events
on the Sun.
Primary author
Lakshmi Pradeep Chitta
(Max Planck Institute for Solar System Research)