A solar filament disconnected by magnetic reconnection

Abstract

Aims. We aim to study a high-resolution observation of an asymmetric inflow magnetic reconnection between a filament and its surrounding magnetic loops in active region NOAA 12436 on 2015 October 23. Methods. We analyzed the multiband observations of the magnetic reconnection obtained by the New Vacuum Solar Telescope (NVST) and the Solar Dynamic Observatory. We calculated the NVST Hα Dopplergrams to determine the Doppler properties of the magnetic reconnection region and the rotation of a jet. Results. The filament firstly becomes active and then approaches its southwestern surrounding magnetic loops (L1) with a velocity of 9.0 km s−1. During this period, the threads of the filament become loose in the reconnection region and then reconnect with L1 in turn. L1 is pressed backward by the filament with a velocity of 5.5 km s−1, and then the magnetic reconnection occurs between them. A set of newly formed loops are separated from the reconnection site with a mean velocity of 127.3 km s−1. In the middle stage, some threads of the filament return back first with a velocity of 20.1 km s−1, and others return with a velocity of 4.1 km s−1 after about 07:46 UT. Then, L1 also begins to return with a velocity of 3.5 km s−1 at about 07:47 UT. At the same time, magnetic reconnection continues to occur between them until 07:51 UT. During the reconnection, a linear typical current sheet forms with a length of 5.5 Mm and a width of 1.0 Mm, and a lot of hot plasma blobs are observed propagating from the typical current sheet. During the reconnection, the plasma in the reconnection region and the typical current sheet always shows redshifted feature. Furthermore, the material and twist of the filament are injected into the newly longer-formed magnetic loops by the magnetic reconnection, which leads to the formation of a jet, and its rotation. Conclusions. The observational evidence for the asymmetric inflow magnetic reconnection is investigated. We conclude that the magnetic reconnection does occur in this event and results in the disconnection of the filament. The looseness of the filament may be due to the pressure imbalance between the inside and outside of the filament. The redshifted feature in the reconnection site can be explained by the expansion of the right flank of the filament to the lower atmosphere because of the complex magnetic configuration in this active region.

Reconfiguration and Eruption of a Solar Filament by Magnetic Reconnection with an Emerging Magnetic Field

“…In AIA EUV channels, the width (0.9-2.2 Mm) and length (3.4-14.2 Mm) of the current sheets are consistent with those in Xue et al (2016Xue et al ( , 2020 and Li et al (2021a), but larger than those in and Xue et al (2018). Moreover, the reconnection rate (0.08-0.41) is identical to those in Xue et al (2016), Xue et al (2018), andLi et al (2021a), but larger than those in Xue et al (2020). In NVST Hα images, a similar reconnection rate (0.11-0.6) to that in AIA EUV channels is obtained.…”

“…The details of reconnection between the filament and its nearby emerging magnetic fields are investigated. In AIA EUV channels, the width (0.9-2.2 Mm) and length (3.4-14.2 Mm) of the current sheets are consistent with those in Xue et al (2016Xue et al ( , 2020 and Li et al (2021a), but larger than those in and Xue et al (2018). Moreover, the reconnection rate (0.08-0.41) is identical to those in Xue et al (2016), Xue et al (2018), andLi et al (2021a), but larger than those in Xue et al (2020).…”

Formation of solar coronal loops through magnetic reconnection in an emerging active region

“…Yan et al 2018;Li et al 2018). The thickness of the plasma sheet is ∼1.4 Mm, which is comparable to the thickness of the plasma sheet in a small C1.6 flare (Tian et al 2014) and in two chromospheric reconnection events (Yang et al 2015;Xue et al 2018). It is much smaller than the typical thickness of current sheets measured at a distance of ∼1.5 solar radii or beyond during coronal mass ejections (CMEs, e.g., Lin et al 2009).…”

“…This suggests that the bright plasma sheet is likely a current sheet or contains a current sheet, which can also be observed at different spatial scales (e.g., Tian et al 2014;Yang et al 2015;Xue et al 2018; Yan et al 2018;Li et al 2018). The thickness of the plasma sheet is ∼1.4 Mm, which is comparable to the thickness of the plasma sheet in a small C1.6 flare (Tian et al 2014) and in two chromospheric reconnection events (Yang et al 2015;Xue et al 2018). It is much smaller than the typical thickness of current sheets measured at a distance of ∼1.5 solar radii or beyond during coronal mass ejections (CMEs, e.g., Lin et al 2009).…”

“…Since the magnetic field lines have different polarities between the two approaching side loops, electric current would be built at their interface. This suggests that the bright plasma sheet is likely a current sheet or contains a current sheet, which can also be observed at different spatial scales (e.g., Tian et al 2014;Yang et al 2015;Xue et al 2018; 4 (c) and in the temporal frequency domain. The fitting spectral index α in the frequency range of 0.44−39.81 mHz is -0.92.…”