Homologous flaring activity over a sunspot light bridge in an emerging active region

Abstract

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, reach projected heights of about 98 Mm, and emerge from the same spatial location for nearly 14 hrs, after which they cease completely. A non-linear 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.

Accepted for publication in The Astrophysical Journal Letters, 8 pages, 5 figures, 1 animation

References in corpus (8)

• The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: SHARPs -- Space-weather HMI Active Region Patches
• Preprocessing of vector magnetograph data for a non-linear force-free magnetic field reconstruction
• Nonlinear force-free modeling of the solar coronal magnetic field
• Small-scale chromospheric jets above a sunspot light bridge
• Surge-like oscillations above sunspot light bridges driven by magnetoacoustic shocks
• Chromospheric Plasma Ejections in a Light Bridge of a Sunspot
• The formation of an atypical sunspot light bridge as a result of large-scale flux emergence
• Three-minute Sunspot Oscillations Driven by Magnetic Reconnection in a Light Bridge

Cited by in corpus (3)

• Physical properties of a fan-shaped jet backlit by an X9.3 flare
• Magnetic activities and parameters of 43 flare stars in the GWAC archive
• Sustained heating of the chromosphere and transition region over a sunspot light bridge