Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userObservations and 3D MHD Modeling of a Confined Helical Jet Launched by a Filament Eruption
100
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present a detailed analysis of a confined filament eruption and jet associated with a C1.5 class solar flare. Multi-wavelength observations from GONG and SDO reveal the filament forming over several days following the emergence and then partial cancellation of a minority polarity spot within a decaying bipolar active region. The emergence is also associated with the formation of a 3D null point separatrix that surrounds the minority polarity. The filament eruption occurs concurrent with brightenings adjacent to and below the filament, suggestive of breakout and flare reconnection, respectively. The erupting filament material becomes partially transferred into a strong outflow jet (~ 60 km/s) along coronal loops, becoming guided back towards the surface. Utilising high resolution H$alpha$ observations from SST/CRISP, we construct velocity maps of the outflows demonstrating their highly structured but broadly helical nature. We contrast the observations with a 3D MHD simulation of a breakout jet in a closed-field background and find close qualitative agreement. We conclude that the suggested model provides an intuitive mechanism for transferring twist/helicity in confined filament eruptions, thus validating the applicability of the breakout model not only to jets and coronal mass ejections but also to confined eruptions and flares.
rate research
Read More
Force-free equilibria containing two vertically arranged magnetic flux ropes of like chirality and current direction are considered as a model for split filaments/prominences and filament-sigmoid systems. Such equilibria are constructed analytically through an extension of the methods developed in Titov & Demoulin (1999) and numerically through an evolutionary sequence including shear flows, flux emergence, and flux cancellation in the photospheric boundary. It is demonstrated that the analytical equilibria are stable if an external toroidal (shear) field component exceeding a threshold value is included. If this component decreases sufficiently, then both flux ropes turn unstable for conditions typical of solar active regions, with the lower rope typically being unstable first. Either both flux ropes erupt upward, or only the upper rope erupts while the lower rope reconnects with the ambient flux low in the corona and is destroyed. However, for shear field strengths staying somewhat above the threshold value, the configuration also admits evolutions which lead to partial eruptions with only the upper flux rope becoming unstable and the lower one remaining in place. This can be triggered by a transfer of flux and current from the lower to the upper rope, as suggested by the observations of a split filament in Paper~I (Liu et al. 2012). It can also result from tether-cutting reconnection with the ambient flux at the X-type structure between the flux ropes, which similarly influences their stability properties in opposite ways. This is demonstrated for the numerically constructed equilibrium.
Coronal implosions - the convergence motion of plasmas and entrained magnetic field in the corona due to a reduction in magnetic pressure - can help to locate and track sites of magnetic energy release or redistribution during solar flares and eruptions. We report here on the analysis of a well-observed implosion in the form of an arcade contraction associated with a filament eruption, during the C3.5 flare SOL2013-06-19T07:29. A sequence of events including magnetic flux-rope instability and distortion, followed by filament eruption and arcade implosion, lead us to conclude that the implosion arises from the transfer of magnetic energy from beneath the arcade as part of the global magnetic instability, rather than due to local magnetic energy dissipation in the flare. The observed net contraction of the imploding loops, which is found also in nonlinear force-free field extrapolations, reflects a permanent reduction of magnetic energy underneath the arcade. This event shows that, in addition to resulting in expansion or eruption of overlying field, flux-rope instability can also simultaneously implode unopened field due to magnetic energy transfer. It demonstrates the partial opening of the field scenario, which is one of the ways in 3D to produce a magnetic eruption without violating the Aly-Sturrock hypothesis. In the framework of this observation we also propose a unification of three main concepts for active region magnetic evolution, namely the metastable eruption model, the implosion conjecture, and the standard CSHKP flare model.
Magnetic reconnection modulated by non-local disturbances in the solar atmosphere has been investigated theoretically, but rarely observed. In this study, employing Ha and extreme ultraviolet (EUV) images and line of sight magnetograms, we report acceleration of reconnection by adjacent filament eruption. In Ha images, four groups of chromospheric fibrils are observed to form a saddle-like structure. Among them, two groups of fibrils converge and reconnect. Two newly reconnected fibrils then form, and retract away from the reconnection region. In EUV images, similar structures and evolution of coronal loops are identified. Current sheet forms repeatedly at the interface of reconnecting loops, with width and length of 1-2 and 5.3-7.2 Mm, and reconnection rate of 0.18-0.3. It appears in the EUV low-temperature channels, with average differential emission measure (DEM) weighed temperature and EM of 2 MK and 2.5*10^27 cm-5. Plasmoids appear in the current sheet and propagate along it, and then further along the reconnection loops. The filament, located at the southeast of reconnection region, erupts, and pushes away the loops covering the reconnection region. Thereafter, the current sheet has width and length of 2 and 3.5 Mm, and reconnection rate of 0.57. It becomes much brighter, and appears in the EUV high-temperature channels, with average DEM-weighed temperature and EM of 5.5 MK and 1.7*10^28 cm-5. In the current sheet, more hotter plasmoids form. More thermal and kinetic energy is hence converted. These results suggest that the reconnection is significantly accelerated by the propagating disturbance caused by the nearby filament eruption.
We analyze multi-wavelength and multi-viewpoint observations of a helically twisted plasma jet formed during a confined filament eruption on 10-11 April 2013. Given a rather large scale event with its high spatial and temporal resolution observations, it allows us to clearly understand some new physical details about the formation and triggering mechanism of twisting jet. We identify a pre-existing flux rope associated with a sinistral filament, which was observed several days before the event. The confined eruption of the filament within a null point topology, also known as an Eiffel tower (or inverted-Y) magnetic field configuration results in the formation of a twisted jet after the magnetic reconnection near a null point. The sign of helicity in the jet is found to be the same as that of the sign of helicity in the filament. Untwisting motion of the reconnected magnetic field lines gives rise to the accelerating plasma along the jet axis. The event clearly shows the twist injection from the pre-eruptive magnetic field to the jet.
We study a sequence of eruptive events including filament eruption, a GOES C4.3 flare and a coronal mass ejection. We aim to identify the possible trigger(s) and precursor(s) of the filament destabilisation; investigate flare kernel characteristics; flare ribbons/kernels formation and evolution; study the interrelation of the filament-eruption/flare/coronal-mass-ejection phenomena as part of the integral active-region magnetic field configuration; determine Halpha line profile evolution during the eruptive phenomena. Multi-instrument observations are analysed including Halpha line profiles, speckle images at Halpha-0.8 AA and Halpha+0.8 AA from IBIS at DST/NSO, EUV images and magnetograms from the SDO, coronagraph images from STEREO and the X-ray flux observations from FERMI and GOES. We establish that the filament destabilisation and eruption are the main trigger for the flaring activity. A surge-like event with a circular ribbon in one of the filament footpoints is determined as the possible trigger of the filament destabilisation. Plasma draining in this footpoint is identified as the precursor for the filament eruption. A magnetic flux emergence prior to the filament destabilisation followed by a high rate of flux cancelation of 1.34$times10^{16}$ Mx s$^{-1}$ is found during the flare activity. The flare X-ray lightcurves reveal three phases that are found to be associated with three different ribbons occurring consecutively. A kernel from each ribbon is selected and analysed. The kernel lightcurves and H alpha line profiles reveal that the emission increase in the line centre is stronger than that in the line wings. A delay of around 5-6 mins is found between the increase in the line centre and the occurrence of red asymmetry. Only red asymmetry is observed in the ribbons during the impulsive phases. Blue asymmetry is only associated with the dynamic filament.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
