Observational study on the fine structure and dynamics of a solar jet. II. Energy release process revealed by spectral analysis

Abstract

We report a solar jet phenomenon associated with the C5.4 class flare on 2014 November 11. The data of jet was provided by Solar Dynamics Observatory (SDO), X-Ray Telescope (XRT) aboard Hinode, Interface Region Imaging Spectrograph (IRIS) and Domeless Solar Telescope (DST) at Hida Observatory, Kyoto University. These plentiful data enabled us to present this series of papers to discuss the entire processes of the observed phenomena including the energy storage, event trigger, and energy release. In this paper, we focus on the energy release process of the observed jet, and mainly describe our spectral analysis on the Hα data of DST to investigate the internal structure of the Hα jet and its temporal evolution. This analysis reveals that in the physical quantity distributions of the Hα jet, such as line-of-sight velocity and optical thickness, there is a significant gradient in the direction crossing the jet. We interpret this internal structure as the consequence of the migration of energy release site, based on the idea of ubiquitous reconnection. Moreover, by measuring the horizontal flow of the fine structures in jet, we succeeded in deriving the three-dimensional velocity field and the line-of-sight acceleration field of the Hα jet. The analysis result indicates a part of ejecta in the Hα jet experienced the additional acceleration after it had been ejected from the lower atmosphere. This secondary acceleration was specified to occur in the vicinity of the intersection between the trajectories of the Hα jet and X-ray jet observed by Hinode/XRT. We propose that a fundamental cause of this phenomenon is the magnetic reconnection involving the plasmoid in the observed jet.

Observation and modelling of solar jets

“…Subarcsecond plasmoids were detected by the IRIS, whose average size is about 0.57 Mm, and their ejecting speed ranges from 10 to 220 km s −1 [135]. Besides the observation of plasmoids in straight anemone jets [81,[136][137][138][139], they were also observed in two-sided-loop jets [44] (figure 4). Analysis results indicated that plasmoids observed in different types of jets were similar, and they were thought to be created by magnetic reconnection as a result of the tearing instability of the current sheets.…”

Observation and Modeling of Solar Jets

“…Subarcsecond plasmoids were detected by the IRIS, whose average size is about 0.57 Mm, and their ejecting speed ranges from 10 to 220 km s −1 [135]. Besides the observation of plasmoids in straight anemone jets [81,[136][137][138][139], they were also observed in two-sided-loop jets [43] (see Figure 4). Analysis results indicated that plasmoids observed in different types of jets were similar, and they were thought to be created by magnetic reconnection as a result of tearing instability of the current sheets.…”

Small-scale Turbulent Motion of the Plasma in a Solar Filament as the Precursor of Eruption

“…To compute the LOS velocity and the micro-turbulence inside a filament, we utilised a cloud model first proposed by Beckers (1964). Assuming that (1) the source function is constant along the wavelengths and (2) along the LOS direction and that (3) the line absorption coefficient is a Gaussian shape, this model enables us to determine four physical parameters of the plasma cloud, the source function, the Doppler width, the Doppler shift, and the optical depth (Morimoto & Kurokawa 2003a,b;Morimoto et al 2010;Cabezas et al 2017;Sakaue et al 2018;Seki et al 2017Seki et al , 2019. The LOS velocity (v los ) and the micro-turbulence (ξ) at each pixel were calculated from the Doppler shift (∆λ S ) and the Doppler width (∆λ D ), respectively, based on the equations below (Morimoto & Kurokawa 2003a);…”