A Search for the Counterparts of Quiet-Sun Radio Transients in Extreme Ultraviolet Data

Mondal, Surajit

doi:10.1007/s11207-021-01877-3

Cited by 16 publications

(17 citation statements)

References 21 publications

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“…The most interesting work, in the present context, is by Mondal et al (2020a), which presents convincing evidence for weak and impulsive narrowband emissions at the milli-Solar Flux Unit (mSFU; 1 SFU = 10 4 Jy) level from the quiet Sun regions. Estimates for the energy deposited in the corona by groups of such emissions lies close to the nanoflare regime (Mondal 2021). There is, hence, a promising possibility that these could be the radio counterparts of the so-called "nanoflares," the small energy releases originally hypothesized by Parker (1988) as a potential resolution to the coronal heating puzzle.…”

Section: Introductionmentioning

confidence: 96%

Detection of Ubiquitous Weak and Impulsive Nonthermal Emissions from the Solar Corona

Sharma

Oberoi

Battaglia

et al. 2022

ApJ

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A ubiquitous presence of weak energy releases is one of the most promising hypotheses to explain coronal heating, referred to as the nanoflare hypothesis. The accelerated electrons associated with such weak heating events are also expected to give rise to coherent impulsive emission via plasma instabilities in the meterwave radio band, making this a promising spectral window to look for their presence. Recently Mondal et al. reported the presence of weak and impulsive emissions from quiet Sun regions which seem to meet the requirements of being radio counterparts of the hypothesized nanoflares. Detection of such low-contrast weak emission from the quiet Sun is challenging and, given their implications, it is important to confirm their presence. In this work, using data from the Murchison Widefield Array, we explore the use of an independent robust approach for their detection by separating the dominant, slowly varying component of emission from the weak impulsive one in the visibility domain. We detect milli-Solar Flux Unit-level bursts taking place all over the Sun and characterize their brightness temperatures, distributions, morphologies, durations, and associations with features seen in extreme-UV images. We also attempt to constrain the energies of the nonthermal particles using inputs from the FORWARD coronal model along with some reasonable assumptions, and find them to lie in the subpico flare (∼1019–1021 erg) range. In the process, we also discover perhaps the weakest type III radio burst and another that shows clear signatures of the weakest quasi-periodic pulsations.

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Section: Introductionmentioning

confidence: 96%

Detection of Ubiquitous Weak and Impulsive Nonthermal Emissions from the Solar Corona

Sharma

Oberoi

Battaglia

et al. 2022

ApJ

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“…They also found these emissions to be present throughout the quiet Sun. Mondal (2021) has demonstrated, although in a single instance, that the energy associated with a group of these transients is ∼10 25 erg. These observations suggest the possibility that these transients are the radio counterparts of the longhypothesized nanoflares.…”

Section: Introductionmentioning

confidence: 99%

Study of Radio Transients from the Quiet Sun during an Extremely Quiet Time

Mondal

Oberoi

Biswas

2023

ApJ

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In this work, we study a class of recently discovered meter-wave solar transients referred to as Weak Impulsive Narrowband Quiet Sun Emission (WINQSEs). Their strength is a few percent of the quiet Sun background and is characterized by their very impulsive, narrowband, and ubiquitous presence in quiet Sun regions. Mondal et al. (2020) hypothesized that these emissions might be the radio counterparts of nanoflares, and their potential significance warrants detailed studies. Here we present an analysis of data from an extremely quiet time and with improved methodology over the previous work. As before, we detect numerous WINQSEs, which we have used for their further characterization. Their key properties, namely, their impulsive nature and ubiquitous presence in the quiet Sun, are observed in these data as well. Interestingly, we also find some of the observed properties to differ significantly from the earlier work. With this demonstration of routine detection of WINQSEs, we hope to engender interest in the larger community to build a deeper understanding of WINQSEs.

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“…Radio observations have also presented strong evidence regarding the presence of nonthermal electrons in the quiet solar corona. Mondal et al (2020) reported the detection of Weak Impulsive Narrowband Quiet Sun Emissions (WINQSEs) which the authors hypothesize are weaker cousins of the well known type III radio burst and originate due to coherent plasma emission from nonthermal electrons generated in nanoflares (Mondal 2021).…”

Section: Introductionmentioning

confidence: 99%

Multifrequency microwave imaging of weak transients from the quiet solar corona

Mondal¹,

Chen²,

Yu³

2023

Preprint

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Understanding the dynamics of the quiet solar corona is important for answering key questions including the coronal heating problem. Multiple studies have suggested small-scale magnetic reconnection events may play a crucial role. These reconnection events are expected to involve accelerating electrons to suprathermal energies, which can then produce nonthermal observational signatures. However, due to the paucity of sensitive high-fidelity observations capable of probing these nonthermal signatures, most studies were unable to quantify their nonthermal nature. Here we use joint radio observations from the Very Large Array (VLA) and the Expanded Owens Valley Solar Array (EOVSA) to detect transient emissions from the quiet solar corona in the microwave (GHz) domain. While similar transients have been reported in the past, their nonthermal nature could not be adequately quantified due to the unavailability of broadband observations. Using a much larger bandwidth available now with the VLA and EOVSA, in this study, we are able to quantify the nonthermal energy associated with two of these transients. We find that the total nonthermal energy associated with some of these transients can be comparable to or even larger than the total thermal energy of a nanoflare, which underpins the importance of nonthermal energy in the total coronal energy budget.

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A Search for the Counterparts of Quiet-Sun Radio Transients in Extreme Ultraviolet Data

Cited by 16 publications

References 21 publications

Detection of Ubiquitous Weak and Impulsive Nonthermal Emissions from the Solar Corona

Detection of Ubiquitous Weak and Impulsive Nonthermal Emissions from the Solar Corona

Study of Radio Transients from the Quiet Sun during an Extremely Quiet Time

Multifrequency microwave imaging of weak transients from the quiet solar corona

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