Detections of stellar coronal mass ejections (CMEs) are still rare. Observations of strong Balmer line asymmetries during flare events have been interpreted as being caused by CMEs. Here, we aim to estimate the maximum possible Balmer line fluxes expected from CMEs to infer their detectability in spectroscopic observations. Moreover, we use these results together with a model of intrinsic CME rates to infer the potentially observable CME rates for stars of different spectral types under various observing conditions, as well as the minimum required observing time to detect stellar CMEs in Balmer lines. We find that generally CME detection is favoured for mid- to late-type M dwarfs, as they require the lowest signal-to-noise ratio for CME detection, and the fraction of observable-to-intrinsic CMEs is largest. They may require, however, longer observing times than stars of earlier spectral types at the same activity level, as their predicted intrinsic CME rates are lower. CME detections are generally favoured for stars close to the saturation regime, because they are expected to have the highest intrinsic rates; the predicted minimum observing time to detect CMEs on just moderately active stars is already >100 h. By comparison with spectroscopic data sets including detections as well as non-detections of CMEs, we find that our modelled maximum observable CME rates are generally consistent with these observations on adopting parameters within the ranges determined by observations of solar and stellar prominences.
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.
The effects of a large coronal mass ejection (CME) on a solar coronal streamer located roughly 90 degrees from the main direction of the CME propagation observed on January 2, 2012 by the SOHO/LASCO coronagraph are analyzed. Radial coronal streamers undergo some bending when CMEs pass through the corona, even at large angular distances from the streamers. The phenomenon resembles a bending wave traveling along the streamer. Some researchers interpret these phenomena as the effects of traveling shocks generated by rapid CMEs, while others suggest they are waves excited inside the streamers by e…
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。
On 2015 January 6-7, an interplanetary coronal mass ejection (ICME) was observed at L1. This event, which can be associated with a weak and slow coronal mass ejection, allows us to discuss on the differences between the boundaries of the magnetic cloud and the compositional boundaries. A fast stream from a solar coronal hole surrounding this ICME offers a unique opportunity to check the boundaries' process definition and to explain differences between them. Using Wind and ACE data, we perform a complementary analysis involving compositional, magnetic, and kinematic observations providing relev…
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…
Jets are defined as impulsive, well-collimated upflows, occurring in different layers of the solar atmosphere with different scales. Their relationship with coronal mass ejections (CMEs), another type of solar impulsive events, remains elusive. Using the high-quality imaging data of AIA/SDO, here we show a well-observed coronal jet event, in which part of the jets, with the embedding coronal loops, runs into a nearby coronal hole (CH) and gets bounced towards the opposite direction. This is evidenced by the flat-shape of the jet front during its interaction with the CH and the V-shaped feature…
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…
We report observations of a two-stage coronal dimming in an eruptive event of a two-ribbon flare and a fast coronal mass ejection (CME). Weak gradual dimming persists for more than half an hour before the onset of the two-ribbon flare and the fast rise of the CME. It is followed by abrupt rapid dimming. The two-stage dimming occurs in a pair of conjugate dimming regions adjacent to the two flare ribbons, and the flare onset marks the transition between the two stages of dimming. At the onset of the two-ribbon flare, transient brightenings are also observed inside the dimming regions, before ra…
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…
We report ground based, low frequency heliograph (80 MHz), spectral (85-35 MHz) and polarimeter (80 and 40 MHz) observations of drifting, non-thermal radio continuum associated with the `halo' coronal mass ejection (CME) that occurred in the solar atmosphere on 2013 March 15. The magnetic field strengths ($B$) near the radio source were estimated to be $B \approx 2.2 \pm 0.4$ G at 80 MHz and $B \approx 1.4 \pm 0.2$ G at 40 MHz. The corresponding radial distances ($r$) are $r \approx 1.9~R_{\odot}$ (80 MHz) and $r \approx 2.2~R_{\odot}$ (40 MHz).
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…
We study the role of the coronal magnetic field configuration of an active region in determining the propagation direction of a coronal mass ejection (CME). The CME occurred in the active region 11944 (S09W01) near the disk center on 2014 January 7 and was associated with an X1.2 flare. A new CME reconstruction procedure based on a polarimetric technique is adopted, which shows that the CME changed its propagation direction by around 28$^\circ$ in latitude within 2.5 R$_\odot$ and 43$^\circ$ in longitude within 6.5 R$_\odot$ with respect to the CME source region. This significant non-radial mo…
We present the multi-point and multi-wavelength observation and analysis on a solar coronal jet and coronal mass ejection (CME) event in this paper. Employing the GCS model, we obtained the real (three-dimensional) heliocentric distance and direction of the CME and found it propagate in a high speed over 1000 km/s . The jet erupted before and shared the same source region with the CME. The temporal and spacial relation- ship between them guide us the possibility that the jet triggered the CME and became its core. This scenario could promisingly enrich our understanding on the triggering mechan…
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…
We have performed, for the first time, the successful automated detection of Coronal Mass Ejections (CMEs) in data from the inner heliospheric imager (HI-1) cameras on the STEREO A spacecraft. Detection of CMEs is done in time-height maps based on the application of the Hough transform, using a modified version of the CACTus software package, conventionally applied to coronagraph data. In this paper we describe the method of detection. We present the result of the application of the technique to a few CMEs that are well detected in the HI-1 imagery, and compare these results with those based o…
During eruptive solar flares and coronal mass ejections, a non-pot{\-}ential magnetic arcade with much excess magnetic energy goes unstable and reconnects. It produces a twisted erupting flux rope and leaves behind a sheared arcade of hot coronal loops. We suggest that: the twist of the erupting flux rope can be determined from conservation of magnetic flux and magnetic helicity and equipartition of magnetic helicity. It depends on the geometry of the initial pre-eruptive structure. Two cases are considered, in the first of which a flux rope is not present initially but is created during the e…
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…
We report here on the determination of plasma physical parameters across a shock driven by a Coronal Mass Ejection using White Light (WL) coronagraphic images and Radio Dynamic Spectra (RDS). The event analyzed here is the spectacular eruption that occurred on June 7th 2011, a fast CME followed by the ejection of columns of chromospheric plasma, part of them falling back to the solar surface, associated with a M2.5 flare and a type-II radio burst. Images acquired by the SOHO/LASCO coronagraphs (C2 and C3) were employed to track the CME-driven shock in the corona between 2-12 R$_\odot$ in an an…
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.
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…
Coronal mass ejections (CMEs) with angular width $> 30^{\circ}$ have been observed to occur at a higher rate during solar cycle 24 compared to cycle 23, per sunspot number. This result is supported by data from three independent databases constructed using Large Angle and Spectrometric Coronagraph Experiment (LASCO) coronagraph images, two employing automated detection techniques and one compiled manually by human observers. According to the two databases that cover a larger field of view, the enhanced CME rate actually began shortly after the cycle 23 polar field reversal, in 2004, when the p…
Solar coronal dimmings have been observed extensively in the past two decades. Due to their close association with coronal mass ejections (CMEs), there is a critical need to improve our understanding of the physical processes that cause dimmings as well as their relationship with CMEs. In this study, we investigate coronal dimmings by combining simulation and observational efforts. By utilizing a data-constrained global magnetohydrodynamics model (AWSoM: Alfven-wave Solar Model), we simulate coronal dimmings resulting from different CME energetics and flux rope configurations. We synthesize th…
We present a comprehensive analysis of a particular class of coronal mass ejection (CME) event, called streamer-blowout CME (SBOs). The events are characterized by a gradual swelling of the overlying streamer, lasting hours to days, followed by a slow, wide CME, generally exhibiting a 3-part structure, which leaves the streamer significantly depleted in its wake. We identify 909 SBO events in the LASCO/C2 observations between 1996 and 2015. The average blowout lasts for 40.5 hours but the evacuation can take days for some events. SBO-CMEs are wider and more massive than the average CME. Their …
Extreme ultraviolet (EUV) coronal dimmings are often observed in response to solar eruptive events. These phenomena can be generated via several different physical processes. For space weather, the most important of these is the temporary void left behind by a coronal mass ejection (CME). Massive, fast CMEs tend to leave behind a darker void that also usually corresponds to minimum irradiance for the cooler coronal emissions. If the dimming is associated with a solar flare, as is often the case, the flare component of the irradiance light curve in the cooler coronal emission can be isolated an…
Estimated relations at a shock driven by a coronal mass ejection
SOHO/LASCO C3数据的分析揭示了一个不连续性，解释为一个冲击波，在一个有限的区域内的等离子体密度径向分布在每一个前面的10个选定的日冕物质抛射（CME）沿其行进方向。在各种事件中，冲击波速度为$V\approx$ 800-2500 km s $^{-1}$。将阿尔文马赫数$M_A$对激波强度$ρ_2/ρ_1$的依赖关系（在距太阳中心$R > 10R_\odot$测得）与理想MHD计算进行比较，表明表征激波阵面内部过程的有效绝热指数$γ$在很大程度上介于2和5/3之间。这对应于运动自由度的有效数量2至3。对于地球的弓形激波和行星际无碰撞激波，也导出了类似的依赖关系，即$M_A(ρ_2/ρ_1)$。所有这些都支持了CME前的间断是无碰撞激波的假设。
We report observations of thermal emission from the frontal structure of a coronal mass ejection (CME) using data obtained with the Gauribidanur RAdioheliograPH (GRAPH) simultaneously at 80 MHz and 53 MHz on 2016 May 1. The CME was due to activity on the far-side of the Sun, but near its limb. No non-thermal radio burst activity were noticed. This provided an opportunity to observe the faint thermal radio emission from the CME, and hence directly estimate the electron density, mass, and magnetic field strength of the plasma entrained in the CME. Considering that CMEs are mostly observed only i…
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.
Solar flares and coronal mass ejections (CMEs) are the most powerful explosions in the Sun. They are major sources of potentially destructive space weather conditions. However, the possible causes of their initiation remain controversial. By using high resolution data observed by NST of BBSO, supplemented by Solar Dynamics Observatory (SDO) observations, we present unusual observations of a small-scale emerging flux rope near a large sunspot, whose eruption produced an M-class flare and a coronal mass ejection. The presence of the small-scale flux rope was indicated by static nonlinear force f…
