Formation And Eruption Of Solar Filament

Solar filaments are one of special features in the solar atmosphere,consisted of cool,dense plasma,which suspend in extremely hot and thin solar corona.When they are observed on the solar disk,they appear as dark filamentary structures called filaments.In contrast,it is well to know as prominences when they are seen above the solar limb,where they appear as bright features against the dark background.These filaments or prominences usually lie above the magnetic polarity inversion line on the photosphere.One of hot topics in the solar physics is to understand filament.It is still not clear that what the magnetic structure of the filament is,because of the difficulty to directly measure the magnetic field in the chromosphere and corona.Many questions in the filament are still controversial,such as,how to form the magnetic structure of the filament,how to transport the plasma into filaments,what trigger the filament eruption and the physical mechanism in the eruption,what is the evolution of the physical parameters in the filament during the formation and eruption,and so on.To deal with these questions,we study on the formation and eruption of the filament,by using multi-band,imaging and spectroscopic,high temporal and spatial resolution data observed by ground-and space-based telescopes.It is useful to understand the solar filament.In this article,we will review the background about the filament and introduce main telescopes in the word.And then,our three works studied on the filament have been showed.Firstly,the evolution of the electric current during the formation and eruption of filaments.Secondly,the formation and eruption of the filament.Thirdly,the investigation of the filament material injection.In our first work,by using observation data from the Solar Dynamics Observatory and New Vacuum Solar Telescope,we study on the evolution of electric currents associated with two homology filament which appear on the same place in the active region NOAA 11884.According to the vector magnetograms observed by Heliospheric and Magnetic Imager and Ampere's law,the electric current component perpendicular to the photosphere(vertical electric current)can be directly calculated.With using the three dimension magnetic field in the corona derived by non-linear force free model extrapolation,we make two cross-sections to investigate the horizontal electric current along the axis of each filament.The results show that the vertical currents of the entire active region behaved with a decreasing trend and the magnetic fields also kept decreasing during the long-term evolution.For the eruption-related evolution,the mean transverse field strengths decreased before two eruptions and increased sharply after two eruptions in the vicinity of the polarity inversion lines underneath the filament.The related vertical current showed different behaviors in two of the eruptions.On the other hand,a very interesting feature was found: opposite horizontal currents with respect to the current of the filament.s axis appeared and increased under the filament before the eruptions and disappeared after the eruptions.We suggest that these opposite currents were carried by the new flux emerging from the photosphere bottom and might be the trigger mechanism for these filament eruptions.In the second work,we intensively study on the formation and eruption of a filament which locals on the active region NOAA 12241 during the period from 2014 December 18 to 19,using multi-band observation data from ground-and space-based telescopes.By using the vector magnetograms from SDO/HMI and combining with some equations,some physical parameters(such as helicity injection rate,lorentz force and vertical electric current)can be calculated.The helicity injection rate before eruption is found to be larger than that after eruption,while the vertical electric current undergoes an increase at first and then a gradual decrease,similar to what the magnetic flux undergoes.Meanwhile,we find that the right part of the filament is formed by magnetic reconnection between two bundles of magnetic field lines while the left part originated from shearing motion.The interaction of the two parts causes the eruption of this filament.The mean horizontal magnetic fields in the vicinity of the magnetic polarity inversion line(PIL)enhance rapidly during the eruption.Another striking phenomenon,where the vertical electric currents close to the magnetic PIL suddenly expand toward two sides during the eruption,is found.We propose that this fascinating feature is associated with the release of energy during the eruption.In the third work,we mainly focus on the material injection of the filament.The formation of a filament associated with a series of jets,which the filament was from absent to present in the active region NOAA 12574,had been studied in detail.By using observation from many ground-and space-based telescopes,it was found that a lot of cool materials were directly lifted into the corona by a serious of jets nearby the right foot-point of filament and became the filament materials.Simultaneously,the magnetic flux emergence was found on the photosphere in the vicinity of the right foot-point of the filament.These suggested that cool materials in the low atmosphere can be directly injected into the filament in the corona and jets would be caused by the magnetic reconnection through the interaction of pre-existed magnetic fields and new emergence magnetic fields.Studying on a jet at 18:02 on Aug 11 in detail with NST/BBSO Tio observations,it was found that the dark threads grew or emerged in the vicinity of the right foot-point after the jet and the transverse velocity of heated plasma along the filament axis was about 157.6 km/s.On the other hand,using with Hida/DST observation,we found that the jetted plasma by a jet at 00:42 on Aug 12 was rotation.Therefore,we concluded that the jet not only supplied the materials for the filament,but also injected the helicity into the filament simultaneously.This article focus on one of the hottest topic in the solar physics: the formation and eruption of the filament.In order to research this topic,we show three investigation related to the filament,using observations from many telescopes.Through the above researches,it is useful to understand the solar filament.