SOHO任务期间对极紫外线和可见日冕的高质量天气观测的可用性提高了我们对CME低日冕表现的理解。EUV成像仪/白光日冕仪的连接已经被证明是如此强大，通常假设当日冕仪观察到CME时，如果没有EUV特征，那么事件必须起源于可见的边缘。这一假设对空间天气预报有很大的影响，但尚未得到检验。本文提出了第一次详细分析的正面，大规模的日冕物质抛射，没有明显的对应物在低日冕。SECCHI仪器观察到该事件。COR2A日冕物质抛射观测到慢磁绳型日冕物质抛射，而COR2B日冕物质抛射观测到极微弱的部分晕。该事件发展非常缓慢，是典型的拖缆井喷CME类。EUVI A 171图像显示，在东翼上方有一个凹形特征，在爆发前两天左右相对稳定，当时它上升到日冕区域并发展成为CME的核心。在EUVI-B图像中没有观察到CME的典型低日冕特征，我们将其归因于通量绳升空的异常大的高度。这种解释得到了CME质量测量和预期EUV调光强度估计的支持。多亏了这两个视角的可用性，我们才能够确定可能的来源区域。这一事件起源于宁静的太阳上的一条中性线。在磁盘的可见（从STEREO B）面上的任何地方都不存在活动区域。在太阳盘面上没有留下任何痕迹，这一观测结果明确地表明，CME爆发不需要有明确的盘面特征。
英文摘要：
The availability of high quality synoptic observations of the EUV and visible corona during the SOHO mission has advanced our understanding of the low corona manifestations of CMEs. The EUV imager/white light coronagraph connection has been proven so powerful, it is routinely assumed that if no EUV signatures are present when a CME is observed by a coronagraph, then the event must originate behind the visible limb. This assumption carries strong implications for space weather forecasting but has not been put to the test. This paper presents the first detailed analysis of a frontside, large-scale CME that has no obvious counterparts in the low corona. The event was observed by the SECCHI instruments. The COR2A coronagraph observed a slow flux-rope type CME, while an extremely faint partial halo was observed in COR2B. The event evolved very slowly and is typical of the streamer-blowout CME class. EUVI A 171 images show a concave feature above the east limb, relatively stable for about two days before the eruption, when it rises into the coronagraphic fields and develops into the core of the CME. None of the typical low corona signatures of a CME were observed in the EUVI-B images, which we attribute to the unusually large height from which the flux-rope lifted off. This interpretation is supported by the CME mass measurements and estimates of the expected EUV dimming intensity. Only thanks to the availability of the two viewpoints we were able to identify the likely source region. The event originated along a neutral line over the quiet sun. No active regions were present anywhere on the visible (from STEREO B) face of the disk. Leaving no trace behind on the solar disk, this observation shows unambiguously that a CME eruption does not need to have clear on-disk signatures.
We present an algorithm to detect the outer edges of Coronal Mass Ejection (CME) events as seen in differences of Heliospheric Imager STEREO SECCHI HI-1 images from either A or B spacecraft, as well as its implementation in Python.
We report on the first detection of nonthermal radio emission associated with a polar coronal mass ejection. We call the radio emission as diffuse interplanetary radio emission (DIRE), which occurs in the decameter-hectometric wavelengths. The radio emission originates from the shock flanks that interact with nearby streamers.
We present a python-based tool to detect the occultation of background sources by foreground Solar coronal mass ejections. The tool takes as input standard celestial coordinates of the source and translates those to the Helioprojective plane, and is thus well suited for use with a wide variety of background astronomical sources. This tool provides an easy means to search through a large archival dataset for such crossings and relies on the well-tested Astropy and Sunpy modules.
On Formation Of A Shock Wave In Front Of A Coronal Mass Ejection With Velocity Exceeding The Critical One
新的研究证实了[M]中的结论。Eselevich，and V. Eselevich，2008];根据该理论，在日冕物质抛射前，存在一个沿CME传播方向扩展的扰动区，其速度$u$相对于周围日冕等离子体低于临界$u_C$。扰动区的时间差亮度（等离子体密度）在CME前向更远的距离平滑地减小。在扰动区的前部，在高于$u_C$的u处形成激波，表现为亮度差径向分布的不连续性。
We report observations of the total solar eclipse of 14 December 2020, during which a coronal mass ejection can be see n propagating. A comprehensive set of photographs covering a high dynamic range of exposure allow to characterize its dimensions. The displacement of the front can be seen occurring during the few minutes of totality.
Coronal mass ejections (CMEs) are huge expulsions of magnetized matter from the Sun and stars, traversing space with speeds of millions of kilometers per hour. Solar CMEs can cause severe space weather disturbances and consumer power outages on Earth, whereas stellar CMEs may even pose a hazard to the habitability of exoplanets. While CMEs ejected by our Sun can be directly imaged by white-light coronagraphs, for stars this is not possible. So far, only a few candidates for stellar CME detections are reported. Here we demonstrate a different approach, based on sudden dimmings in the extreme-ul…
We present a detailed three-dimensional (3D) view of a prominence eruption, coronal loop expansion, and coronal mass ejections (CMEs) associated with an M4.4 flare that occurred on 2011 March 8 in the active region NOAA 11165. Full-disk H$α$ images of the flare and filament ejection were successfully obtained by the Flare Monitoring Telescope (FMT) following its relocation to Ica University, Peru. Multiwavelength observation around the H$α$ line enabled us to derive the 3D velocity field of the H$α$ prominence eruption. Features in extreme ultraviolet were also obtained by the Atmospheric Imag…
The triggering process for coronal mass ejections (CME) in the solar atmosphere is not fully understood. We use observations from different spacecraft at several wavelengths to detect an instability process for a prominence/filament with a subsequent eruption of CME. Time series of spectral lines at 304, 171, 193, and 211 Å have been obtained with the SDO spacecraft, and at 304, 171, 195, and 284 Å with the STEREO spacecraft. A prominence/filament system was observed during November 8-23, 2011, at different angles by SDO, STEREO_A, and STEREO_B. The observations show that a giant tornado began…
The Sun is the major source of heat and light in our solar system. The solar cycle is the 11-year cycle of solar activity that can be determined by the rise and fall in the numbers and surface area of sunspots. Solar activity is associated with several factors including radio flux, solar irradiance, magnetic field, solar flares, coronal mass ejections, and solar cycles. This study attempts to determine the Sun's activity specifically for the coronal mass ejection, its trend during solar cycle 23, and its apparent difference. A time series analysis was used to measure the CME data for larger ca…
Coronal mass ejections (CMEs) are the primary drivers of severe space weather disturbances in the heliosphere. Models of CME dynamics have been proposed that do not fully include the effects of magnetic reconnection on the forces driving the ejection. Both observations and numerical modeling, however, suggest that reconnection likely plays a major role in most, if not all, fast CMEs. Here, we theoretically investigate the accretion of magnetic flux onto a rising ejection by reconnection involving the ejection's background field. This reconnection alters the magnetic structure of the ejection a…
In situ measurements of interplanetary coronal mass ejection (ICME) composition, including elemental abundances and charge states of heavy ions, open a new avenue to study coronal mass ejections (CMEs) besides remote-sensing observations. The ratios between different elemental abundances can diagnose the plasma origin of CMEs (e.g., from the corona or chromosphere/photosphere) due to the first ionization potential (FIP) effect, which means elements with different FIP get fractionated between the photosphere and corona. The ratios between different charge states of a specific element can provid…
The role of active region coronal magnetic field in determining coronal mass ejection propagation direction
研究了活动区日冕磁场位形在决定日冕物质抛射（CME）传播方向中的作用。2014年1月7日，CME发生在盘中心附近的活动区11944（S09W01），与X1.2耀斑有关。采用一种新的基于偏振技术的CME重建方法，结果表明CME相对于CME源区的传播方向在2.5 R $_\odot$内的纬度上改变了28 $^\circ$，在6.5 R $_\odot$内的经度上改变了43 $^\circ$.这种显著的非径向运动与M $\ddot{o}$ stl等人（2015）的发现一致。我们使用非线性无力场（NLFFF）和位场源面（PFSS）外推方法来确定日冕磁场的位形。根据外推结果计算了不同高度处的磁能密度分布。结果表明，活动区日冕磁场对日冕物质抛射的传播方向有很强的影响。这与活动区日冕磁场本身的“通道”相一致，而不是附近结构的偏转。这些结果表明，要正确确定日冕物质抛射的传播方向，必须考虑活动区日冕磁场的位形。
Solar flares (SFs) are sudden brightening observed over the Sun surface which is associated with a large energy release. Flares with burst of Xray emission are normally followed by a mass ejection of electrons and ions from the solar atmosphere called Coronal Mass Ejections (CMEs). There is an evidence that solar magnetic field can change its configuration through reconnection and release energy, accelerating solar plasma causing SFs and CMEs. This study examines the SFs and CMEs data from SOHO and GOES satellites during the very low solar activity year of 2009 and moderately high solar activi…
Coronal Mass Ejections (CMEs) contributes to the perturbation of solar wind in the heliosphere. Thus, depending on the different phases of the solar cycle and the rate of CME occurrence, contribution of CMEs to solar wind parameters near the Earth changes. In the present study, we examine the long term occurrence rate of CMEs, their speeds, angular widths and masses. We attempt to find correlation between near sun parameters, determined using white light images from coronagraphs, with solar wind measurements near the Earth from in-situ instruments. Importantly, we attempt to find what fraction…
Physical Conditions of Coronal Plasma at the transit of a Shock driven by a Coronal Mass Ejection
本文报道了利用白光日冕图像和射电动力学谱确定由日冕物质抛射驱动的冲击波的等离子体物理参数。这里分析的事件是发生在2011年6月7日的壮观爆发，一个快速的CME，随后是色球等离子体柱的喷射，其中一部分落回太阳表面，与M2.5耀斑和II型射电爆发有关。SOHO/LASCO日冕仪（C2和C3）获得的图像被用来跟踪日冕中2-12 R $_\odot$之间的日冕物质抛射驱动的激波，角度间隔约为110 $^\circ$。在这些时间间隔，我们推导出2维（2D）的电子密度，冲击波速度和冲击压缩比的地图，我们测量的冲击倾斜角相对于径向方向。在合理的假设下，这些量被用来推断激波马赫数$M_\text{A}$和激波高度处日冕磁场强度的二维图。我们发现，在早期阶段（2-4 R $_\odot$），整个激波面是超阿尔夫文型的，而在以后（即更高的位置），它只在头部变成超阿尔夫文型的。这与观测到的II型爆发源的位置一致，这是从RDS结合来自WL的冲击运动学和日冕密度推断的。第一次，一个日冕冲击是用来获得一个2D地图的日冕磁场强度超过10 R $_\odot$高度和$\sim 110^\circ$纬度间隔。
Stellar coronal mass ejections (CMEs) are a growing research field, especially during the past decade. The large number of so far detected exoplanets raises the open question for the CME activity of stars, as CMEs may strongly affect exoplanetary atmospheres. In addition, as CMEs contribute to stellar mass- and angular momentum loss and are therefore relevant for stellar evolution, there is need for a better characterization of this phenomenon. In this article we review the different methodologies used up to now to attempt the detection of stellar CMEs. We discuss the limitations of the differ…
Large-scale propagating fronts are frequently observed during solar eruptions, yet it is open whether they are waves or not, partly because the propagation is modulated by coronal structures, whose magnetic field we still cannot measure. However, when a front impacts coronal structures, an opportunity arises for us to look into the magnetic properties of both interacting parties in the low-$β$ corona. Here we studied large-scale EUV fronts accompanying three coronal mass ejections (CMEs), each originating from a kinking rope-like structure in the NOAA active region (AR) 12371. These eruptions …
Upcoming missions, including the James Webb Space Telescope, will soon characterize the atmospheres of terrestrial-type exoplanets in habitable zones around cool K- and M-type stars searching for atmospheric biosignatures. Recent observations suggest that the ionizing radiation and particle environment from active cool planet hosts may be detrimental for exoplanetary habitability. Since no direct information on the radiation field is available, empirical relations between signatures of stellar activity, including the sizes and magnetic fields of starspots, are often used. Here, we revisit the …
An onboard automated coronal mass ejections (CMEs) detection algorithm has been developed for Visible Emission Line Coronagraph (VELC) onboard ADITYA-L1. The aim of this algorithm is to reduce the load on telemetry by sending the high spatial ($\sim$ 2.51 arcsec pixel$^{-1}$) and temporal (1 s) resolution images of corona from 1.05 R$_{\odot}$ to 3 R$_{\odot}$, containing CMEs and rejecting others. It is based on intensity thresholding followed by an area thresholding in successive running difference images which are re-binned to lower resolution to improve signal to noise. Here we present the…
Recently, we developed the Correlation-Aided Reconstruction (CORAR) method to reconstruct solar wind inhomogeneous structures, or transients, using dual-view white-light images (Li et al. 2020; Li et al. 2018). This method is proved to be useful for studying the morphological and dynamical properties of transients like blobs and coronal mass ejection (CME), but the accuracy of reconstruction may be affected by the separation angle between the two spacecraft (Lyu et al. 2020). Based on the dual-view CME events from the Heliospheric Imager CME Join Catalogue (HIJoinCAT) in the HELCATS (Heliosphe…
Based on the method of finding coronal magnetic field value radial profiles B(R) described in (Gopalswamy and Yashiro, 2011), and applied for the directions close to the sky plane, we determined magnetic field value radial distributions along the directions close to the Sun-Earth axis. For this purpose, by using the method in (Xue, Wang, and Dou, 2005), from the SOHO/LASCO data, we found 3D characteristics for fast halo coronal mass ejections (HCMEs) and for the HCME-related shocks. Through these data, we managed to obtain the B(R) distributions as far as 43 solar radii from the Sun center, wh…
Solar coronal dimmings have been observed extensively in the past two decades and are believed to have close association with coronal mass ejections (CMEs). Recent study found that coronal dimming is the only signature that could differentiate powerful ares that have CMEs from those that do not. Therefore, dimming might be one of the best candidates to observe the stellar CMEs on distant Sun-like stars. In this study, we investigate the possibility of using coronal dimming as a proxy to diagnose stellar CMEs. By simulating a realistic solar CME event and corresponding coronal dimming using a g…
