Related papers: Quiet Sun impulsive events observed with NuSTAR du…
We present the first results of a search for transient hard X-ray (HXR) emission in the quiet solar corona with the \textit{Nuclear Spectroscopic Telescope Array} (\textit{NuSTAR}) satellite. While \textit{NuSTAR} was designed as an…
We present the first survey of quiet Sun features observed in hard X-rays (HXRs), using the the Nuclear Spectroscopic Telescope ARray (NuSTAR), a HXR focusing optics telescope. The recent solar minimum combined with NuSTAR's high…
In this paper, we use a highly sensitive telescope to characterize solar X-ray transients ranging from microflares in active regions down to weakly energetic brightenings in the quiet Sun. X-rays are closely linked to the initial energy…
The explanation of the coronal heating problem potentially lies in the existence of nanoflares, numerous small-scale heating events occuring across the whole solar disk. In this paper, we present the first imaging spectroscopy X-ray…
We present the first observations of quiescent active regions (ARs) using NuSTAR, a focusing hard X-ray telescope capable of studying faint solar emission from high temperature and non-thermal sources. We analyze the first directly imaged…
We present X-ray imaging spectroscopy of one of the weakest active region (AR) microflares ever studied. The microflare occurred at $\sim$11:04 UT on 2018 September 9 and we studied it using the Nuclear Spectroscopic Telescope ARray…
We report a NuSTAR observation of a solar microflare, SOL2015-09-01T04. Although it was too faint to be observed by the GOES X-ray Sensor, we estimate the event to be an A0.1 class flare in brightness. This microflare, with only 5 counts…
Solar flares are explosive releases of magnetic energy. Hard X-ray (HXR) flare emission originates from both hot (millions of Kelvin) plasma and nonthermal accelerated particles, giving insight into flare energy release. The Nuclear…
We analyzed ground-based low frequency ($<$100\,MHz) radio spectral and imaging data of the solar corona obtained with the facilities in the Gauribidanur observatory during the same time as the very weak soft X-ray flares (sub A-class, flux…
NuSTAR is a highly sensitive focusing hard X-ray (HXR) telescope and has observed several small microflares in its initial solar pointings. In this paper, we present the first joint observation of a microflare with NuSTAR and Hinode/XRT on…
Solar flares, with energies ranging over several orders of magnitude, result from impulsive release of energy due to magnetic reconnection in the corona. Barring a handful, almost all microflares observed in X-rays are associated with the…
Much evidence suggests that the solar corona is heated impulsively, meaning that nanoflares may be ubiquitous in quiet and active regions (ARs). Hard X-ray (HXR) observations with unprecedented sensitivity $>$3~keV are now enabled by…
We present the first joint observation of a small microflare in X-rays with the Nuclear Spectroscopic Telescope ARray (NuSTAR), UV with the Interface Region Imaging Spectrograph (IRIS) and EUV with the Solar Dynamics Observatory/Atmospheric…
The goal of the Miniature X-ray Solar Spectrometer (MinXSS) CubeSat is to explore the energy distribution of soft X-ray (SXR) emissions from the quiescent Sun, active regions, and during solar flares, and to model the impact on Earth's…
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…
Solar active regions contain a broad range of temperatures, with the thermal plasma distribution often observed to peak in the few millions of kelvin. Differential emission measure (DEM) analysis can allow instruments with diverse…
Elements with low First Ionization Potential (FIP) are known to be three to four times more abundant in active region loops of the solar corona than in the photosphere. There have been observations suggesting that this observed "FIP bias"…
We present observations of the occulted active region AR12222 during the third {\em NuSTAR} solar campaign on 2014 December 11, with concurrent {\em SDO/}AIA and {\em FOXSI-2} sounding rocket observations. The active region produced a…
We present the first joint spectral and imaging analysis of hard X-ray (HXR) emission from 3 microflares observed by the Nuclear Spectroscopic Telescope ARray (NuSTAR) and Solar Orbiter/Spectrometer/Telescope for Imaging X-rays (STIX). We…
Microflares are energetically smaller versions of solar flares, demonstrating the same processes of plasma heating and particle acceleration. However, it remains unclear down to what energy scales this impulsive energy release continues,…