A tiny event producing an interplanetary type III burst

Abstract

We investigate the conditions under which small scale energy release events in the low corona gave rise to strong interplanetary (IP) type III bursts. We analyze observations of three tiny events, detected by the Nan\c cay Radio Heliograph (NRH), two of which produced IP type IIIs. We took advantage of the NRH positioning information and of the high cadence of AIA/SDO data to identify the associated EUV emissions. We measured positions and time profiles of the metric and EUV sources. We found that the EUV events that produced IP type IIIs were located near a coronal hole boundary, while the one that did not was located in a closed magnetic field region. In all three cases tiny flaring loops were involved, without any associated mass eruption. In the best observed case the radio emission at the highest frequency (435 MHz) was displaced by ~55" with respect to the small flaring loop. The metric type III emission shows a complex structure in space and in time, indicative of multiple electron beams, despite the low intensity of the events. From the combined analysis of dynamic spectra and NRH images we derived the electron beam velocity as well as the height, ambient plasma temperature and density at the level of formation of the 160 MHz emission. From the analysis of the differential emission measure derived from the AIA images we found that the first evidence of energy release was at the footpoints and this was followed by the development of flaring loops and subsequent cooling. We conclude that even small energy release events can accelerate enough electrons to give rise to powerful IP type III bursts. The proximity of the electron acceleration site to open magnetic field lines facilitates the escape of the electrons into the interplanetary space. The offset between the site of energy release and the metric type III location warrants further investigation.

Accepted for publication in Astronomy & Astrophysics

References in corpus (6)

• Statistical Survey of Type III Radio Bursts at Long Wavelengths Observed by the Solar TErrestrial RElations Observatory (STEREO)/Waves Instruments: Radio Flux Density Variations with Frequency
• The Low-High-Low Trend of Type III Radio Burst Starting Frequencies and Solar Flare Hard X-rays
• Microwave and EUV Observations of an Erupting Filament and Associated Flare and CME
• Flare-associated type III radio bursts and dynamics of the EUV jet from SDO/AIA and RHESSI observations
• Are there Radio-quiet Solar Flares?
• Hot coronal loops associated with umbral brightenings

Cited by in corpus (9)

• Observations of solar X-ray and EUV jets and their related phenomena
• LOFAR observations of fine spectral structure dynamics in type IIIb radio bursts
• Solar Physics with the Square Kilometre Array
• Type III Solar Radio Burst Source Region Splitting Due to a Quasi-Separatrix Layer
• A Statistical Study of Solar Radio Type III Bursts and Space Weather Implication
• A weak coronal heating event associated with periodic particle acceleration episodes
• Transient brightenings in the quiet Sun detected by ALMA at 3 mm
• Interplanetary Type IV Bursts
• Evidence for two-loop interaction from IRIS and SDO observations of penumbral brightenings