Solar coronal mass ejections are the most energetic events in the Solar System. In their standard formation model, a magnetic flux rope builds up into a coronal mass ejection through magnetic reconnection that continually converts overlying, untwisted magnetic flux into twisted flux enveloping the pre-existing rope. However, only a minority of coronal mass ejections carry a coherent magnetic flux rope as their core structure, which casts doubt on the universality of this orderly wrapping process. Here we provide observational evidence of a different formation and eruption mechanism of a magnetic flux rope from an S-shaped thread, where its magnetic flux is fully replaced via flare reconnections. One of the footpoints of the sigmoidal feature slipped and expanded during the formation, and then moved to a completely new place, associated with the highly dynamical evolution of flare ribbons and a twofold increase in magnetic flux through the footpoint, during the eruption. Such a configuration is not predicted by standard formation models or numerical simulations and highlights the three-dimensional nature of magnetic reconnections between the flux rope and the surrounding magnetic field.
Context: Many previous studies have shown that the magnetic precursor of a coronal mass ejection (CME) takes the form of a magnetic flux rope, and a subset of them have become known as `hot flux ropes' due to their emission signatures in $\sim$10 MK plasma. Aims: We seek to identify the processes by which these hot flux ropes form, with a view of developing our understanding of CMEs and thereby improving space weather forecasts. Methods: Extreme-ultraviolet observations were used to identify five pre-eruptive hot flux ropes in the solar corona and study how they evolved. Confined flares were o…
We present evidence that a magnetic flux rope was formed before a coronal mass ejection (CME) and its associated long-duration flare during a pair of preceding confined eruptions and associated impulsive flares in a compound event in NOAA Active Region 12371. Extreme-ultraviolet images and the extrapolated nonlinear force-free field show that the first two, impulsive flares, SOL2015-06-21T01:42, result from the confined eruption of highly sheared low-lying flux, presumably a seed flux rope. The eruption spawns a vertical current sheet, where magnetic reconnection creates flare ribbons and loop…
We compare the magnetic helicity in the 17-18 March 2013 interplanetary coronal mass ejection (ICME) flux-rope at 1 AU and in its solar counterpart. The progenitor coronal mass ejection (CME) erupted on 15 March 2013 from NOAA active region 11692 and associated with an M1.1 flare. We derive the source region reconnection flux using post-eruption arcade (PEA) method (Gopalswamy et al. 2017a) that uses the photospheric magnetogram and the area under the PEA. The geometrical properties of the near-Sun flux rope is obtained by forward-modeling of white-light CME observations. Combining the geometr…
The recent launch of Solar Orbiter and BepiColombo opened a brief window in which these two spacecraft were positioned in a constellation that allows for the detailed sampling of any Earth-directed CMEs. Fortunately, two such events occurred with in situ detections of an ICME by Solar Orbiter on the 19th of April and the 28th of May 2020. These two events were subsequently also observed in situ by BepiColombo and Wind around a day later. We attempt to reconstruct the observed in situ magnetic field measurements for all three spacecraft simultaneously using an empirical magnetic flux rope model…
We quantitatively address the conjecture that magnetic helicity must be shed from the Sun by eruptions launching coronal mass ejections in order to limit its accumulation in each hemisphere. By varying the ratio of guide and strapping field and the flux rope twist in a parametric simulation study of flux rope ejection from approximately marginally stable force-free equilibria, different ratios of self- and mutual helicity are set and the onset of the torus or helical kink instability is obtained. The helicity shed is found to vary over a broad range from a minor to a major part of the initial …
The Sun's atmosphere is frequently disrupted by coronal mass ejections (CMEs), coupled with flares and energetic particles. In the standard picture, the coupling is explained by magnetic reconnection at a vertical current sheet connecting the flare loops and the CME, with the latter embedding a helical magnetic structure known as flux rope. As it jumps upward due to instabilities or loss of equilibrium, the flux rope stretches the overlying coronal loops so that oppositely directed field is brought together underneath, creating the current sheet. However, both the origin of flux ropes and thei…
Sigmoid-to-Flux-Rope Transition Leading to A Loop-Like Coronal Mass Ejection
S型面是太阳爆发最重要的前兆结构之一。在这封信中,我们研究了2010年8月1日的S型喷发,使用太阳动力学观测站(SDO)上的大气成像组件(AIA)获得的EUV数据。在AIA 94(Fe XVIII; 6 MK)中,首次明确观察到由于系链切割重连引起的拓扑重构,即,两个相对的J形环重新连接形成一个连续的S形环,其中心部分沿着磁极性反转线(PIL)倾斜并对齐,以及一个穿过PIL的紧凑环。光球流和日冕系绳切割重连之间的因果关系证明了持续收敛流朝向PIL使用视线磁图获得的日震和磁成像仪(HMI)上SDO的检测。S形环在低日冕中保持准平衡状态约50分钟,中央下沉部分以约10 km s-1的速度缓慢上升。然后在GOES级C3.2耀斑爆发前10分钟,速度增加到约60 km s-1,因为S形环加速了其向拱形环的转变,最终导致环状日冕物质抛射(CME)。AIA的观察结合H?滤波图以及硬X射线(HXR)成像和光谱学与大多数耀斑环是一致的,所述耀斑环是通过将包裹上升通量绳的较少剪切的J形环的拉伸腿重新连接而形成的,与标准的系绳切割方案一致。
Forecasting the geomagnetic effects of solar storms, known as coronal mass ejections (CMEs), is currently severely limited by our inability to predict the magnetic field configuration in the CME magnetic core and by observational effects of a single spacecraft trajectory through its 3D structure. CME magnetic flux ropes can lead to continuous forcing of the energy input to the Earth's magnetosphere by strong and steady southward-pointing magnetic fields. Here, we demonstrate in a proof-of-concept way a new approach to predict the southward field Bz in a CME flux rope. It combines a novel semi-…
We present a major update to the 3D coronal rope ejection (3DCORE) technique for modeling coronal mass ejection flux ropes in conjunction with an Approximate Bayesian Computation (ABC) algorithm that is used for fitting the model to in situ magnetic field measurements. The model assumes an empirically motivated torus-like flux rope structure that expands self-similarly within the heliosphere, is influenced by a simplified interaction with the solar wind environment, and carries along an embedded analytical magnetic field. The improved 3DCORE implementation allows us to generate extremely large…
Interplanetary coronal mass ejections (ICMEs) often consist of a shock wave, sheath region, and ejecta region. The ejecta regions are divided into two broad classes: magnetic clouds (MC) that exhibit the characteristics of magnetic flux ropes and non-magnetic clouds (NMC) that do not. As CMEs result from eruption of magnetic flux ropes, it is important to answer why NMCs do not have the flux rope features. One claims that NMCs lose their original flux rope features due to the interactions between ICMEs or ICMEs and other large scale structures during their transit in the heliosphere. The other…
Context: Late on 2013 August 19, a coronal mass ejection (CME) erupted from an active region located near the far-side central meridian from Earth's perspective. The event and its accompanying shock were remotely observed by the STEREO-A, STEREO-B and SOHO spacecraft. The interplanetary counterpart (ICME) was intercepted by MESSENGER near 0.3 au, and by both STEREO-A and STEREO-B, near 1 au, which were separated by 78° in heliolongitude. The main objective of this study is to follow the radial and longitudinal evolution of the ICME throughout the inner heliosphere, and to examine possible scen…
Formation and Eruption of a Vortex-driven Magnetic Flux Rope in the Simulated Quiet Sun
School of Astronomy and Space Science, Nanjing University(南京大学天文与空间科学学院);Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education(南京大学现代天文与天体物理教育部重点实验室)
Coronal Mass Ejections (CMEs) are major drivers of extreme space weather conditions, this being a matter of serious concern for our modern technologically-dependent society. Development of numerical approaches that would simulate CME generation and propagation through the interplanetary space is an important step towards our capability to predict CME arrival times at Earth and their geo-effectiveness. In this paper, we utilize a data-constrained Gibson--Low (GL) flux rope model to generate CMEs. We derive the geometry of the initial GL flux rope using the Graduated Cylindrical Shell (GCS) meth…
In this article, we investigate the formation and disruption of a coronal sigmoid from the active region (AR) NOAA 11909 on 07 December 2013, by analyzing multi-wavelength and multi-instrument observations. Our analysis suggests that the formation of `transient' sigmoid initiated $\approx$1 hour before its eruption through a coupling between two twisted coronal loop systems. A comparison between coronal and photospheric images suggests that the coronal sigmoid was formed over a simple $β$-type AR which also possessed dispersed magnetic field structure in the photosphere. The line-of-sight phot…
Zipper reconnection has been proposed as a mechanism for creating most of the twist in the flux tubes that are present prior to eruptive flares and coronal mass ejections. We have conducted a first numerical experiment on this new regime of reconnection, where two initially untwisted parallel flux tubes are sheared and reconnected to form a large flux rope. We describe the properties of this experiment, including the linkage of magnetic flux between concentrated flux sources at the base of the simulation, the twist of the newly formed flux rope and the conversion of mutual magnetic helicity in…
Flux-rope-based magnetohydrodynamic modeling of coronal mass ejections (CMEs) is a promising tool for the prediction of the CME arrival time and magnetic field at Earth. In this work, we introduce a constant-turn flux rope model and use it to simulate the 12-July-2012 16:48 CME in the inner heliosphere. We constrain the initial parameters of this CME using the graduated cylindrical shell (GCS) model and the reconnected flux in post-eruption arcades. We correctly reproduce all the magnetic field components of the CME at Earth, with an arrival time error of approximately 1 hour. We further estim…
Context: On 26-27 January 2020, the wide-field imager WISPR on Parker Solar Probe (PSP) observed a coronal mass ejection (CME) from a distance of approximately 30 solar radii as it passed through the instrument's 95 degree field-of-view, providing an unprecedented view of the flux rope morphology of the CME's internal structure. The same CME was seen by STEREO, beginning on 25 January. Aims: Our goal was to understand the origin and determine the trajectory of this CME. Methods: We analyzed data from three well-placed spacecraft: Parker Solar Probe (PSP), Solar Terrestrial Relations Observator…
We present a magnetohydrodynamic (MHD) simulation of the coronal mass ejection (CME) on 13 December 2006 in the emerging delta-sunspot active region 10930, improving upon a previous simulation by Fan (2016) as follows. (1) Incorporate an ambient solar wind instead of using a static potential magnetic field extrapolation as the initial state. (2) In addition to imposing the emergence of a twisted flux rope, also impose at the lower boundary a random electric field that represents the effect of turbulent convection, which drives field-line braiding and produces resistive and viscous heating in t…