Homologous Flaring Activity over a Sunspot Light Bridge in an Emerging Active Region

Sunspot light bridges are known to exhibit a variety of dynamic and persistent phenomena such as surges, small-scale jets, etc., in the chromosphere and transition region. While it has generally been proposed that magnetic reconnection is responsible for this small-scale dynamism, persistent flaring...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2021-01, Vol.907 (1), p.L4
Main Authors: Louis, Rohan Eugene, Thalmann, Julia K.
Format: Article
Language:English
Subjects:
Bridges
Chromosphere
Collimation
Flares
Fluctuations
Homology
Jets
Light
Magnetic fields
Magnetic flux
Magnetic reconnection
Photosphere
Photospheric magnetic fields
Polarity
Solar activity
Solar observatories
Sunspots
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Summary:Sunspot light bridges are known to exhibit a variety of dynamic and persistent phenomena such as surges, small-scale jets, etc., in the chromosphere and transition region. While it has generally been proposed that magnetic reconnection is responsible for this small-scale dynamism, persistent flaring activity lasting several hours from the same spatial location on a sunspot light bridge has rarely been reported. We combine observations from the Atmospheric Imaging Assembly and the Helioseismic Magnetic Imager on board the Solar Dynamics Observatory to investigate homologous flaring activity over a small sunspot light bridge in an emerging flux region. The homologous flares all produced broad, collimated jets including a B6.4 class flare. The jets rise at a speed of about 200 km s −1 , reach projected heights of about 98 Mm, and emerge from the same spatial location for nearly 14 hrs, after which they cease completely. A nonlinear force-free extrapolation of the photospheric magnetic field shows a low-lying flux rope connecting the light bridge to a remote opposite-polarity network. The persistent flares occur as a result of the rapid horizontal motion of the leading sunspot that causes the relatively vertical magnetic fields in the adjacent umbra to reconnect with the low-lying flux rope in the light bridge. Our results indicate that the flaring ceases once the flux rope has lost sufficient twist through repeated reconnections.
ISSN:2041-8205
2041-8213
DOI:10.3847/2041-8213/abd478