First radio evidence of ubiquitous magnetic reconnections and impulsive heating in the quiet solar corona

Abstract:

In the past decade, significant advances have been made towards understanding and solving the coronal heating problem. However, to the best of our knowledge, much of this work has focused on understanding heating of the corona in the vicinity of the active regions. The quiet corona is also hot, and often comprises the bulk of the corona, so it is equally important to understand the physical processes which maintain this medium at MK temperatures. This presentation will describe the results from our effort to use the data from the Murchison Widefield Array to search for impulsive radio emissions in the quiet solar corona, on a very quiet day. Radio impulsive emissions are an excellent probe of nonthermal emission and can be regarded as the smoking guns for reconnection activity at the site of the nonthermal emission. By pushing the detection threshold of nonthermal emission by about two orders of magnitude lower than previous studies, we have uncovered evidence of ubiquitous presence of reconnections throughout the quiet sun. The corresponding figure submitted with this abstract, shows the histogram of flux density at 4 different frequencies. The powerlaw tail, clearly observed in these figures, are strong evidence for the presence of nonthermal emissions in the quiet solar corona. We have done a robust statistical characterization of these impulsive nonthermal emissions, and show that they satisfy the necessary conditions for them to be important for solar coronal heating. Our rough estimate of the amount of energy which must be dumped into the corona for these emissions to be observed finds it to be roughly comparable to the coronal heating budget. This is the first observational evidence for ubiquitous magnetic reconnections and impulsive heating in the quiet solar corona. We also find many similarities between the statistical distributions of these impulsive emissions and the magnetic switchbacks recently characterized in detail by the Parker Solar Probe. We also hypothesize that the magnetic reconnections which give rise to the switchbacks might also be behind the impulsive emissions which we are detecting in the metrewave band. We are continuing to explore additional aspects of these impulsive emissions, including their time-stationarity. We will also summarize the status of these investigations in this presentation.