A multi-instrument study of UV bursts and associated surges in AR 12957

¹ European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
² Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
³ Solar-Terrestrial Centre of Excellence – SIDC, Royal Observatory of Belgium, Ringlaan -3- Av. Circulaire, 1180 Brussels, Belgium
⁴ Instituto de Astrofísica de Andalucá (IAA-CSIC), Apartado de Correos 3004, E-18080 Granada, Spain
⁵ Universitat de València, Catedrático José Beltrán 2, 46980 Paterna-Valencia, Spain

^⋆ Corresponding author; chris.nelson@esa.int

Received: 19 August 2024
Accepted: 7 October 2024

Abstract

Context. The relationship between UV bursts and solar surges is complex, with these events sometimes being observed together and sometimes being observed independently. Why this sporadic association exists is unknown; however, it likely relates to the physical conditions at the site of the energy release that drives these events.

Aims. Here, we aim to better understand the relationship between UV bursts and solar surges through a multi-instrument analysis of several associated events that occurred around the trailing sunspot in AR 12957.

Methods. We used data from Solar Orbiter, the Solar Dynamics Observatory (SDO), and the Interface Region Imaging Spectrograph (IRIS) to achieve our aims. These data were sampled on 3 March 2022 between 09:30:30 UT and 11:00:00 UT, during which time a coordinated observing campaign associated with the Slow Solar Wind Connection Solar Orbiter Observing Plan (SOOP) took place.

Results. Numerous small-scale negative polarity magnetic magnetic features (MMFs) were observed to move quickly (potentially up to 3.3 km s⁻¹) away from a sunspot until they collided with a more stable positive polarity plage region around 7 Mm away. Several UV bursts were identified in IRIS slit-jaw imager (SJI) 1400 Å data co-spatial to where these opposite polarity fields interacted, with spatial scales (< 2 Mm) and lifetimes (< 20 minutes) larger than typical values for such events. Two surges were also observed to occur at these locations, with one being short (5 Mm) and hot (bright in the IRIS SJI images), whilst the other was a cooler (dark in coronal imaging channels), longer surge that appeared to fill an active region loop.

Conclusions. Magnetic reconnection between the negative polarity MMFs around the sunspot and the positive polarity plage region appears to be the driver of these events. Both the speed of the MMFs and the locally open magnetic topology of the plage region could possibly have been important for forming the surges.