Study of the spatial association between an active region jet and a nonthermal type III radio burst

Abstract

Aims. We aim to investigate the spatial location of the source of an active region (AR) jet and its relation with associated nonthermal type III radio emission. Methods. An emission measure (EM) method was used to study the thermodynamic nature of the AR jet. The nonthermal type III radio burst observed at meterwavelength was studied using the Murchison Widefield Array (MWA) radio imaging and spectroscopic data. The local configuration of the magnetic field and the connectivity of the source region of the jet with open magnetic field structures was studied using a nonlinear force-free field (NLFFF) extrapolation and potential field source surface (PFSS) extrapolation respectively. Results. The plane-of-sky velocity of the AR jet was found to be ∼136 km s−1. The EM analysis confirmed the presence of low temperature 2 MK plasma for the spire, whereas hot plasma, between 5 and 8 MK, was present at the footpoint region which also showed the presence of Fe XVIII emission. A lower limit on the electron number density was found to be 1.4 × 108 cm−3 for the spire and 2.2 × 108 cm−3 for the footpoint. A temporal and spatial correlation between the AR jet and nonthermal type III burst confirmed the presence of open magnetic fields. An NLFFF extrapolation showed that the photospheric footpoints of the null point were anchored at the location of the source brightening of the jet. The spatial location of the radio sources suggests an association with the extrapolated closed and open magnetic fields although strong propagation effects are also present. Conclusions. The multi-scale analysis of the field at local, AR, and solar scales confirms the interlink between different flux bundles involved in the generation of the type III radio signal with flux transferred from a small coronal hole to the periphery of the sunspot via null point reconnection with an emerging structure.

Solar Jets: SDO and IRIS Observations in the Perspective of New MHD Simulations

“…Radio Type III bursts were also often associated with surges, suggesting that surges followed open magnetic field lines or very large loops (Chiuderi-Drago et al, 1986;Kundu et al, 1995). This idea has been confirmed by using NLFFF extrapolation showing how nonthermal types III associated with jets escape along open field lines at the edge of close structures over active regions (Lu et al, 2019;Mulay et al, 2019). Schmieder et al (1983), Schmieder et al (1984) reported on the recurrence of Hα and C IV surges with a time delay between two jet ejections of 15-30 min.…”

Imaging Spectroscopy of CME-associated Solar Radio Bursts using OVRO-LWA

“…Group type IIIs and complex type-III-like fast-drift bursts that occur with CMEs have been claimed to originate variously from shock-accelerated electrons, unspecified "shock-associated" acceleration, or acceleration directly from the flare site (see Cane et al 1981;Kundu & Stone 1984;Dulk et al 2000;Reiner et al 2000;Gopalswamy & Makela 2010 for details). This uncertainty may be resolved with recently available high spatial, spectral, and temporal resolution imaging of type III bursts, which provide key information about reconnection sites and contribute to our understanding of particle acceleration (Chen et al 2013(Chen et al , 2018Mulay et al 2019).…”

A Review of Recent Solar Type III Imaging Spectroscopy

“…For this event, type III imaging spectroscopy was used to ascertain typical electron beam speeds around 0.2c. Comparing with magnetic field extrapolations, Mulay et al (2019) found type III radio sources at the flaring site which did not appear at the expected points along magnetic field lines. There was a distinct absence of type III frequency evolution along the field that would be consistent with electron beam propagation.…”

“…Type IIIs are commonly associated with jets in extreme ultraviolet (EUV) and X-rays (e.g., Bain and Fletcher, 2009;Klassen et al, 2011;Krucker et al, 2011), with electron beams typically following the same path as the jet. A number of studies have analyzed type IIIs using high resolution MWA imaging spectroscopy that occurred co-temporal and co-spatially with jets observed in UV (McCauley et al, 2017;Cairns et al, 2018;Mulay et al, 2019). In all three events the type III emission showed resolved fine temporal structure, consistent with several distinct EUV jet episodes and caused by multiple electron beam injections, explained via energization within magnetic reconnection regions by Cairns et al (2018).…”

“…There was a distinct absence of type III frequency evolution along the field that would be consistent with electron beam propagation. Mulay et al (2019) concluded this was possibly due to radio wave scattering or the magnetic field extrapolation not including local small scale variations.…”