Flares and CMEs are very powerful events in which energetic radiation and particles are ejected within a short time. These events thus can strongly affect planets that orbit these stars. This is particularly relevant for planets of M-stars, because these stars stay active for a long time during their evolution and yet potentially habitable planets orbit at short distance. Unfortunately, not much is known about the relation between flares and CMEs in M-stars as only very few CMEs have so far been observed in M-stars. In order to learn more about flares and CMEs on M-stars we monitored the active M-star EV Lac spectroscopically at high resolution. We find 27 flares with energies between 1.6E31 and 1.4E32 erg in Halpha during 127 hours of spectroscopic monitoring and 49 flares with energies between 6.3E31 and 1.1E33 erg during the 457 hours of TESS observation. Statistical analysis shows that the ratio of the continuum flux in the TESS-band to the energy emitted in Halpha is 10.408 +/- 0.026. Analysis of the spectra shows an increase in the flux of the He II 4686 Å line during the impulsive phase of some flares. In three large flares, we detect a continuum source with a temperature between 6 900 and 23 000 K. In none of the flares we find a clear CME event indicating that these must be very rare in active M-stars. However, in one relatively weak event, we found an asymmetry in the Balmer lines of ~220 km/s which we interpret as a signature of an erupting filament.
This paper studies the magnetic topology of successively erupting active regions (ARs) 11429 and 12371. Employing vector magnetic field observations from Helioseismic and Magnetic Imager, the pre-eruptive magnetic structure is reconstructed by a model of non-linear force-free field (NLFFF). For all the five CMEs from these ARs, the pre-eruptive magnetic structure identifies an inverse-S sigmoid consistent with the coronal plasma tracers in EUV observations. In all the eruption cases, the quasi-separatrix layers (QSLs) of Large Q values are continuously enclosing core field bipolar regions in w…
It is well established that solar eruptions are powered by free magnetic energy stored in current-carrying magnetic field in the corona. It has also been generally accepted that magnetic flux ropes (MFRs) are a critical component of many coronal mass ejections (CMEs). What remains controversial is whether MFRs are present well before the eruption. Our aim is to identify progenitors of MFRs, and investigate pre-eruptive magnetic properties associated with these progenitors. Here we analyze 28 MFRs erupting within 45 deg from the disk center from 2010 to 2015. All MFRs'feet are well identified b…
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…
Coronal Mass Ejections (CMEs) may have major importance for planetary and stellar evolution. Stellar CME parameters, such as mass and velocity, have yet not been determined statistically. So far only a handful of stellar CMEs has been detected mainly on dMe stars using spectroscopic observations. We therefore aim for a statistical determination of CMEs of solar-like stars by using spectroscopic data from the ESO phase 3 and Polarbase archives. To identify stellar CMEs we use the Doppler signal in optical spectral lines being a signature of erupting filaments which are closely correlated to CME…
Solar filaments exist as stable structures for extended periods of time before many of them form the core of a CME. We examine the properties of an erupting filament on 2017 May 29--30 with high-resolution He I 10830 A and Halpha spectra from the Dunn Solar Telescope, full-disk Dopplergrams of He I 10830 A from the Chromospheric Telescope, and EUV and coronograph data from SDO and STEREO. Pre-eruption line-of-sight velocities from an inversion of He I with the HAZEL code exhibit coherent patches of 5 Mm extent that indicate counter-streaming and/or buoyant behavior. During the eruption, indivi…
The magnetic breakout model, in which reconnection in the corona leads to destabilization of a filament channel, explains numerous features of eruptive solar events, from small-scale jets to global-scale coronal mass ejections (CMEs). The underlying multipolar topology, pre-eruption activities, and sequence of magnetic reconnection onsets (first breakout, then flare) of many observed fast CMEs/eruptive flares are fully consistent with the model. Recently, we have demonstrated that most observed coronal-hole jets in fan/spine topologies also are induced by breakout reconnection at the null poin…
Magnetic flux ropes (MFRs), sets of coherently twisted magnetic field lines, are believed as core structures of various solar eruptions. Their evolution plays an important role to understand the physical mechanisms of solar eruptions, and can shed light on adverse space weather near the Earth. However, the erupting MFRs are occasionally prevented by strong overlying magnetic fields, and the MFR evolution during the descending phase in the confined cases is lack of attention. Here, we present the deformation of an erupting MFR accompanied by a confined double-peaked solar flare. The first peak …
We present results from a set of numerical simulations aimed at exploring the mechanism of coronal mass ejection (CME) suppression in active stars by an overlying large-scale magnetic field. We use a state-of-the-art 3D magnetohydrodynamic (MHD) code which considers a self-consistent coupling between an Alfvén wave-driven stellar wind solution, and a first-principles CME model based on the eruption of a flux-rope anchored to a mixed polarity region. By replicating the driving conditions used in simulations of strong solar CMEs, we show that a large-scale dipolar magnetic field of $75$ G is abl…
This paper describes a new SMART/SDDI Filament Disappearance Catalogue, in which we listed almost all the filament disappearance events that the Solar Dynamics Doppler Imager (SDDI) has observed since its installation on the Solar Magnetic Activity Research Telescope (SMART) in May 2016. Our aim is to build a database that can help predict the occurrence and severity of coronal mass ejections (CMEs). The catalogue contains miscellaneous information associated with filament disappearance such as flare, CME, active region, three-dimensional trajectory of erupting filaments, detection in Interpla…
Stealthy Coronal Mass Ejections (CMEs), lacking low coronal signatures, may result in significant geomagnetic storms. However, the mechanism of stealthy CMEs is still highly debated. In this work, we investigate whether there are differences between the stealthy and standard CMEs in terms of their dynamic behaviors. Seven stealthy and eight standard CMEs with slow speeds are selected. We calculate two-dimensional speed distributions of CMEs based on the cross-correlation method, rather than the unidimensional speed, and further obtain more accurate distributions and evolution of CME mechanical…
Solar coronal mass ejections (CMEs) have a strong association with solar flares that is not fully understood. This characteristic of our Sun's magnetic activity may also occur on other stars, but the lack of successfully detected stellar CMEs makes it difficult to perform statistical studies that might show a similar association between CMEs and flares. Because of the potentially strong association, the search for stellar CMEs often starts with a successful search for superflares on magnetically active stars. Regardless of the flare's presence, we emphasize the utility of searching for CME-spe…
Coronal dimmings, localized regions of reduced emission in the EUV and soft X-rays, are interpreted as density depletions due to mass loss during the CME expansion. They contain crucial information on the early evolution of CMEs low in the corona. For 62 dimming events, characteristic parameters are derived, statistically analyzed and compared with basic flare quantities. On average, coronal dimmings have a size of $2.15\times10^{10}$ km$^{2}$, contain a total unsigned magnetic flux of $1.75\times10^{21}$ Mx, and show a total brightness decrease of $-1.91\times10^{6}$ DN, which results in a re…
Motivated by the need to improve the ability to forecast whether a certain coronal mass ejection (CME) is to impact Earth, and by the insufficiency of statistical studies that analyze the whole erupting system with the focus on the governing conditions under CME deflections, we performed a careful analysis of 13 events along a one-year time interval showing large deflections from their source region. We used telescopes imaging the solar corona at different heights and wavelengths on board the Project for Onboard Autonomy 2 (PROBA2), Solar Dynamics Observatory (SDO), Solar TErrestrial RElations…
Coronal mass ejections (CMEs) that exhibit weak or no eruption signatures in the low corona, known as stealth CMEs, are problematic as upon arrival at Earth they can lead to geomagnetic disturbances that were not predicted by space weather forecasters. We investigate the origin and eruption of a stealth event that occurred on 2015 January 3 that was responsible for a strong geomagnetic storm upon its arrival at Earth. To simulate the coronal magnetic field and plasma parameters of the eruption we use a coupled approach. This approach combines an evolutionary nonlinear force-free field model of…
We take a broad look at the problem of identifying the magnetic solar causes of space weather. With the lackluster performance of extrapolations based upon magnetic field measurements in the photosphere, we identify a region in the near UV part of the spectrum as optimal for studying the development of magnetic free energy over active regions. Using data from SORCE, Hubble Space Telescope, and SKYLAB, along with 1D computations of the near-UV (NUV) spectrum and numerical experiments based on the MURaM radiation-MHD and HanleRT radiative transfer codes, we address multiple challenges. These cha…
The Sun is an active star that can launch large eruptions of magnetised plasma into the heliosphere, called coronal mass ejections (CMEs). These ejections can drive shocks that accelerate particles to high energies, often resulting in radio emission at low frequencies (<200 MHz). To date, the relationship between the expansion of CMEs, shocks and particle acceleration is not well understood, partly due to the lack of radio imaging at low frequencies during the onset of shock-producing CMEs. Here, we report multi-instrument radio, white-light and ultraviolet imaging of the second largest flare …
Large-scale solar eruptions have been extensively explored over many years. However, the properties of small-scale events with associated shocks have been rarely investigated. We present the analyses of a small-scale short-duration event originating from a small region. The impulsive phase of the M1.9-class flare lasted only for four minutes. The kinematic evolution of the CME hot channel reveals some exceptional characteristics including a very short duration of the main acceleration phase ($<$ 2 minutes), a rather high maximal acceleration rate ($\sim$50 km s$^{-2}$) and peak velocity ($\sim…
CoSEE-Cat: A Comprehensive Solar Energetic Electron event Catalogue obtained from combined in situ and remote-sensing observations from Solar Orbiter -- Catalogue description and first statistical results
A Possible Stellar CME Event Associated with a Long-duration Optical Flare on the RS CVn-type Star UX Arietis
International Centre of Supernovae (ICESUN), Yunnan Key Laboratory of Supernova Research, Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台）；Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences（中国科学院天体结构与演化重点实验室）；Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）
Stellar flares are characterized by sudden enhancement of electromagnetic radiation from the atmospheres of stars. Compared to their solar counterparts, our knowledge on the coronal plasma dynamics of stellar flares and their connection to coronal mass ejections (CMEs) remains very limited. With time-resolved high-resolution spectroscopic observations from the \textit{Chandra} X-ray observatory, we detected noticeable coronal plasma flows during several stellar flares on a nearby dMe star EV Lac. In the observed spectra of O~{\sc{viii}} (3 MK), Fe~{\sc{xvii}} (6 MK), Mg~{\sc{xii}} (10 MK), and…
APO & SMARTS flare star campaign observations I. Blue wing asymmetries in chromospheric lines during mid M dwarf flares from simultaneous spectroscopic and photometric observation data
本文通过对三颗中期 M 矮星的同时光谱与测光观测，发现 7 次耀发在 Hα 等色球谱线中呈现蓝翼不对称性，并据此估计了可能的暗条爆发质量及其与 CME 的关系。
Violent solar flares and coronal mass ejections (CMEs) are magnetic phenomena. However, how magnetic fields reconnecting in the flare differ from non-flaring magnetic fields remains unclear owing to the lack of studies of the flare magnetic properties. Here we present a first statistical study of flaring (highlighted by flare-ribbons) vector magnetic fields in the photosphere. Our systematic approach allows us to describe key physical properties of solar flare magnetism, including distributions of magnetic flux, magnetic shear, vertical current and net current over flaring versus non-flaring p…
Magnetic flux ropes (MFRs) constitute the core structure of coronal mass ejections (CMEs), but hot debates remain on whether the MFR forms before or during solar eruptions. Furthermore, how flare reconnection shapes the erupting MFR is still elusive in three dimensions. Here we studied a new MHD simulation of CME initiation by tether-cutting magnetic reconnection in a single magnetic arcade. The simulation follows the whole life, including the birth and subsequent evolution, of an MFR during eruption. In the early phase, the MFR is partially separated from its ambient field by a magnetic quasi…
In order to bridge the gap between heliospheric and solar observations of coronal mass ejections (CMEs), one of the key steps is to improve the understanding of their corresponding magnetic structures like the magnetic flux ropes (MFRs). But it remains a challenge to confirm the existence of a coherent MFR before or upon the CME eruption on the Sun and to quantitatively characterize the CME-MFR due to the lack of direct magnetic field measurement in the corona. In this study, we investigate the MFR structures, originating from two active regions (ARs), AR 11719 and AR 12158, and estimate their…
Reconnection Jets Detected during the Footpoint Drift of a CME Flux Rope: New Signatures of Ongoing 3D Arcade-Flux Rope Reconnection
School of Physics and Astronomy, Yunnan University（云南大学物理与天文学院）；Department of Astronomy, Key Laboratory of Astroparticle Physics of Yunnan Province, Yunnan University（云南大学天文学系、云南省天体粒子物理重点实验室）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）
We propose to apply the weighted horizontal magnetic gradient ($WG_{M}$), introduced in Korsos et al (2015), for analysing the pre-flare and pre-CME behaviour and evolution of Active Regions (ARs) using the SDO/HMI-Debrecen Data catalogue. To demonstrate the power of investigative capabilities of the $WG_M$ method, in terms of flare and CME eruptions, we studied two typical ARs, namely, AR 12158 and AR 12192. The choice of ARs represent canonical cases. AR 12158 produced an X1.6 flare with fast "halo" CME ($v_{linear}$=1267 $km s^{-1}$) while in AR 12192 there occurred a range of powerful X-cl…
We analyse the characteristics of interplanetary coronal mass ejections (ICMEs) during Solar Cycles 23 and 24. The present analysis is primarily based on the near-Earth ICME catalogue (Richardson and Cane, 2010). An important aspect of this study is to understand the near-Earth and geoeffective aspects of ICMEs in terms of their association (type II ICMEs) versus absence (non-type II ICMEs) of decameter-hectometer (DH) type II radio bursts, detected by Wind/WAVES and STEREOS/WAVES. Notably, DH type II radio bursts driven by a CME indicate powerful MHD shocks leaving the inner corona and enteri…
