Observations Of Solar Filament Structure And Eruption

The solar filaments are one of the most common and mysterious phenomena in the solar atmosphere.They are consisting of relatively cool and dense magnetized plasma suspended likely clouds in the hot but tenuous corona.Filaments are always observed along photospheric magnetic polarity inversion lines(PIL)that denote filament channels.Typically,a filament is 100 times cooler and denser than its surrounding corona.They are varied inexhaustibly,different in thousands of ways of shapes;being of different sizes and varying lifetime;having dynamical fine structures and bewildering mass flow within;performing beautiful and magnificent eruption but harmful for spaceweather sometimes.Although people have been observing and studying the solar filaments for more than 100 years,there are still many unsolved mysteries,especially the mechanisms and the various physical parameters which operate in the magnetic field configuration,formation,maintenance,instabilities,and eruptions of filaments are not yet clear.In this thesis,We firstly review the background of filaments then summarize the previous researches on filaments observations,classification,magnetic field models,and eruption models.In addition,we also introduced some special types of filament systems,such as “Prominence Pillars” and “Arch Filament System”,and interaction between filaments.Then we introduced the relevant instruments and data,the last part is my own work.Based on high-resolution observations from NVST and SDO,my researches have been mainly carried out with the reconnection between dark fibres and the special structures of double-decker filament as breakthroughs.Our first work investigated successive two-sided loop jets caused by magnetic reconnection between filamentary threads and proposed a new model of two-sided jets.The second work studied the formation and eruption process of a double-decker filament which located on the east limb.Thus we obtained some meaningful conclusions which are helpful to understand the magnetic field structure and the eruption mechanism of filaments.Within this context,we have made an original contribution to knowledge in two areas:1: In Chapter 3 “Successive Two-sided loop Jets Caused by Magnetic Reconnection between Two adjacent Filamentary Threads”,using high temporal and high spatial resolution observations taken by NVST and SDO,we have reported two successive two-sided loop jets that occurred at the southern periphery of NOAA active region 12035.Due to magnetic cancellation and emerging within the source region site of the jets,the two adjacent filamentary threads approached to each other and interacted at the crossing area,which triggered the magnetic reconnection between them.The consequence of the magnetic reconnection further resulted in the opposite plasma ejection along the paths of the two filamentary thread with a typical speed of 150 km s-1.Fifteen minutes later,the second jets similar to first one burst in the same region.Close to the end of the second jet,we report the formation of a bright hot loop structure at the source region,which suggests the formation of new loops during the interaction.The results of our analysis suggest that the two successive two-sided loop jets are the consequence of the magnetic reconnection between two adjacent filamentary threads rather than magnetic reconnection between emerging bipoles and their overlying horizontal magnetic fields as proposed in previous model and observations.Obviously,this is a completely new two-sided jet formation mechanism.2: In Chapter 4 “Formation and Eruption of a Double-decker Filament”,we have presented the observations of a double-decker filament to study its formation,triggering,and eruption physics.It is observed that the double-decker filament was formed by splitting of an original single filament.During the splitting process,intermittent bright point bursts are observed in the filament channel,which resulted in the generation of the upper filament branch.We consider that the splitting of the filament in the present case seems more suitable for the mechanism of mixed kink instability,in which the intermittent bright point bursts underneath the filament may provide successive disturbances to the filament system and therefore trigger or accelerate the external and internal kink instabilities of the filament.The eruption of the newly formed double-decker filament was possibly triggered by two recurrent two-sided loop jets in the filament channel and the continuous mass unloading from the upper filament body.The interaction between the first jet filament directly resulted in the unstable of the lower branch and the fast rising phase of the upper branch.The second jet occurred at the same site about three hours after the first one,which further disturbed and accelerated the rising of the lower filament branch.It is interesting that the rising lower branch overtook the upper one,and then the two branches merged into one filament.Finally,the whole filament erupted violently and caused a large-scale coronal mass ejection,leaving behind a pair of flare ribbons and two dimming regions on the both sides of the filament channel.We consider that the intermittent bursts may directly result in the rearrangement of the filament magnetic field and therefore the formation of the double-decker filament,then the recurrent jets further caused the the fully eruption of the entire filament system.The study provides convincing evidence for supporting the scenario that a double-decker filament can be formed by splitting a single filament into two branches.These findings have implications for,e.g.,our understanding of the relationship between moving magnetic field,filaments/minifilaments formation and eruption mechanisms.We have summarised the final conclusions in Chapter 5,where the potential further investigations and some involved research plans have also been indicated.