The active region source of a type III radio storm observed by Parker Solar Probe during Encounter 2

Abstract

Context. To investigate the source of a type III radio burst storm during encounter 2 of NASA's Parker Solar Probe (PSP) mission. Aims. It was observed that in encounter 2 of NASA's Parker Solar Probe mission there was a large amount of radio activity, and in particular a noise storm of frequent, small type III bursts from 31st March to 6th April 2019. Our aim is to investigate the source of these small and frequent bursts. Methods. In order to do this, we analysed data from the Hinode EUV Imaging Spectrometer (EIS), PSP FIELDS, and the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA). We studied the behaviour of active region 12737, whose emergence and evolution coincides with the timing of the radio noise storm and determined the possible origins of the electron beams within the active region. To do this, we probe the dynamics, Doppler velocity, non-thermal velocity, FIP bias, densities, and carry out magnetic modelling. Results. We demonstrate that although the active region on the disk produces no significant flares, its evolution indicates it is a source of the electron beams causing the radio storm. They most likely originate from the area at the edge of the active region that shows strong blue-shifted plasma. We demonstrate that as the active region grows and expands, the area of the blue-shifted region at the edge increases, which is also consistent with the increasing area where large-scale or expanding magnetic field lines from our modelling are anchored. This expansion is most significant between 1 and 4 April 2019, coinciding with the onset of the type III storm and the decrease of the individual burst's peak frequency, indicating the height at which the peak radiation is emitted increases as the active region evolves.

References in corpus (9)

• A Review of Solar Type III Radio Bursts
• Magnetic connectivity of the ecliptic plane within 0.5 AU : PFSS modeling of the first PSP encounter
• Coronal-Jet-Producing Minifilament Eruptions as a Possible Source of Parker Solar Probe (PSP) Switchbacks
• Modelling of EIS spectrum drift from instrumental temperatures
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• 4D Data Cubes from Radio-Interferometric Spectroscopic Snapshot Imaging
• The drivers of active region outflows into the slow solar wind
• Periodicities in an active region correlated with Type III radio bursts observed by Parker Solar Probe

Cited by in corpus (14)

• Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum
• Upflows in the upper solar atmosphere
• Constraining Global Coronal Models with Multiple Independent Observables
• Linking the Sun to the Heliosphere Using Composition Data and Modelling. A Test Case with a Coronal Jet
• Tracking a beam of electrons from the low solar corona into interplanetary space with the Low Frequency Array, Parker Solar Probe and 1 au spacecraft
• Periodicities in an active region correlated with Type III radio bursts observed by Parker Solar Probe
• Internal Structure of the 2019 April 2 CME
• Widespread Occurrence of High-Velocity Upflows in Solar Active Regions
• Plasma Upflows Induced by Magnetic Reconnection Above an Eruptive Flux Rope
• Signature and escape of highly fractionated plasma in an active region
• Coronal Diagnostics of Solar Type-III Radio Bursts Using LOFAR and PSP Observations
• Coronal electron density: Insights from radio and in situ observations, and EUHFORIA modeling
• Line Profile Studies of Coronal Active Regions in Fe XII λ195.12 Using Hinode/EIS
• Active region upflows in various coronal structures and their coupling to the lower atmosphere