Recently nonthermal radio transients from the quiet sun have been discovered and it has been hypothesised using rough calculations that they might be important for coronal heating. It is well realized that energy calculations using coherent emissions are often subject to poorly constrained parameters and hence have large uncertainties associated with them. However energy estimates using observations in the extreme ultraviolet (EUV) and soft X-ray bands are routinely done and the techniques are pretty well established. This work presents our first attempt to identify the EUV counterparts of these radio transients and then use the counterpart to estimate the energy deposited into the corona during the event. I show that the group of radio transients studied here was associated with an brightening observed in the extreme ultraviolet waveband and was produced due to a flare of energy $\sim 10^{25}$ ergs. The fact that the flux density of the radio transient is only $\sim 2\,$mSFU suggests that it might be possible to do large statistical studies in future for understanding the relationship between these radio transients and other EUV and X-ray counterparts and also for understanding their importance in coronal heating.
In this work we study a class of recently discovered metrewave solar transients referred to as Weak Impulsive Narrowband Quiet Sun Emission \citep[WINQSEs,][]{mondal2020}. Their strength is a few percent of the quiet Sun background and are characterised by their very impulsive, narrow-band and ubiquitous presence in quiet Sun regions. \citet{mondal2020} hypothesised that these emissions might be the radio counterparts of the nanoflares and their potential significance warrants detailed studies. Here we present an analysis of data from an extremely quiet time and with an improved methodology ov…
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 $\rm {<}10^{-7}\,Wm^{-2}$ in the 1\,-\,8\,$\rm Å$ wavelength range) from the `quiet' Sun observed with the X-ray Solar Monitor (XSM) onboard Chandrayaan-2 during the recent solar minimum. Non-thermal type I radio burst activity were noticed in close temporal association with the X-ray events. The estimated brightness temperature ($T_{b}$) of the bursts at a…
We carried out a statistical study of the `quiet' solar corona during the descending phase of the sunspot cycle 24 (i.e. 2015 January - 2019 May) using data obtained with the Gauribidanur RAdioheliograPH (GRAPH) at 53 MHz and 80 MHz simultaneously. Our results show that the equatorial (east-west) diameters of the solar corona at the above two frequencies shrunk steadily. The decrease was found to be due to a gradual reduction in the coronal electron density ($N_{e}$). Independent estimates of $N_{e}$ in the equatorial region of the `background' corona using white-light coronagraph observations…
Observation of High-speed Outflow on Plume-like Structures of the Quiet Sun and Coronal Holes with SDO/AIA
太阳动力学天文台（SDO）上的大气成像组件（AIA）的观测结果显示，在平静的太阳大气层的磁化区域中，存在着无处不在的间歇性外流（喷流），其平均速率约为120 km s-1，温度通常超过100万度。这些外流并不局限于在极冕洞中可见的羽流，也存在于源自赤道冕洞和宁静太阳区域的羽流状结构中。在整个大气层的“羽流间”区域也可以看到外流。此外，在羽流和羽流间区域的这些流动追踪出的结构不断表现出横向（Alfvenic）运动。我们的发现表明，高速外流主要来自安静的太阳和日冕洞的磁网络，并且所观察到的羽流被其中包含的密度更大的等离子体所突出。这些外流可能是一个有效的手段，提供加热的质量进入日冕，并作为一个重要的来源，质量供应的太阳风。我们证明，安静的太阳羽流有时会显着污染相邻冕洞的光谱观测-极大地影响观测到的多普勒频移，从而可能影响这些地区的重大调查。
Radio emission of the quiet Sun is considered to be due to thermal bremsstrahlung emission of the hot solar atmosphere. The properties of the quiet Sun in the microwave band have been well studied, and they can be well described by the spectrum of bremsstrahlung emission. In the meter-wave and decameter-wave bands, properties of the quiet Sun have rarely been studied due to the instrumental limitations. In this work, we use the LOw Frequency ARray (LOFAR) telescope to perform high quality interferometric imaging spectroscopy observations of quiet Sun coronal emission at frequencies below 90~MH…
The focus of this investigation is to quantify the conversion of magnetic to thermal energy initiated by a quiet Sun cancellation event and to explore the resulting dynamics from the interaction of the opposite polarity magnetic features. We used imaging spectroscopy in the H$α$ line, along with spectropolarimetry in the \ion{Fe}{I} 6173~Å and \ion{Ca}{II} 8542~Å lines from the Swedish Solar Telescope (SST) to study a reconnection-related cancellation and the appearance of a quiet Sun Ellerman bomb (QSEB). We observed, for the first time, QSEB signature in both the wings and core of the \ion{F…
Pervasive Linear Polarization Signals in the Quiet Sun
本文利用超深偏振光谱数据研究了宁静太阳网络中线偏振信号的分布。我们减少噪音的意见，尽可能多的是可行的，通过增加单缝测量塞曼敏感的Fe I 630 nm线所采取的日出分光偏振仪。积分斯托克斯光谱用于确定由线偏振信号覆盖的视场的分数。我们发现，在盘中心，高达69%的安静太阳表面显示出振幅大于0.032%的斯托克斯Q或U轮廓（是较长积分所达到的7 x 10^{-5}噪声水平的4.5倍）。在大多数安静的太阳中，仅仅存在线性偏振就意味着弱的网络间场必须高度倾斜，但是我们通过将这些像素与斯托克斯Q或U信号反转来量化这一点。这允许场倾斜、场强度和场方位角的精确确定，因为同时使用所有四个斯托克斯光谱所携带的信息。在1.3 x 10^{-4}的噪声水平下，对53%的观测视场进行反演。因此，导出的磁场分布代表了安静的太阳互联网的一半以上。我们的研究结果证实了从以前的分析中得出的结论，主要使用斯托克斯I和V：互联网络领域是非常倾斜的，但除了在方位角，他们似乎不是各向同性分布。
We report the smallest coronal jets ever observed in the quiet Sun with recent high resolution observations from the High Resolution Telescopes (HRI-EUV and HRI-Lyα) of the Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter. In the HRI-EUV (174 Å) images, these microjets usually appear as nearly collimated structures with brightenings at their footpoints. Their average lifetime, projected speed, width, and maximum length are 4.6 min, 62 km s^(-1), 1.0 Mm, and 7.7 Mm, respectively. Inverted-Y shaped structures and moving blobs can be identified in some events. A subset of these events also …
The goal of this paper is to apply statistical methods to determine electrons densities and their errors from measurements of density-sensitive line intensities in the quiet Sun. Three methods are employed. The first is the use of L-function plots to provide a quick visual assessment of the likelihood that a set of line intensities can provide a robust estimate of these quantities. A second methods involves a chi-squared minimization together with a prescription for determining the regions of statistical confidence in addition to the best-fitting value. A third method uses a Bayesian inference…
Aims. The main aim of the present analysis is to decipher (i) the small-scale bright features in solar images of the quiet Sun and active regions obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) and (ii) the ALMA correspondence of various known chromospheric structures visible in the H-alpha images of the Sun. Methods. Small-scale ALMA bright features in the quiet Sun region were analyzed using single-dish ALMA observations (1.21 mm, 248 GHz) and in an active region using interferometric ALMA measurements (3 mm, 100 GHz). With the single-dish observations, a full-disk sola…
Magnetic reconnection in the quiet Sun is a phenomenon that is consistently observed, and it has recently become feasible to simulate via 3D numerical models of realistically stratified and convection-driven reconnection. We aim to illustrate ways by which quiet Sun fields may contribute to solar atmospheric heating via magnetic reconnection that is driven by convective motion. We also aim to compare our stratified model to earlier idealized coronal models in terms of reconnection drivers and topological conditions. We analyzed a simulation of the quiet Sun in which a complex coronal magnetic …
