Reconnection-generated Plasma Flows in the Quasi-separatrix Layer in Localized Solar Corona

Abstract

Multiwavelength observations of the propagating disturbances (PDs), discovered by Atmospheric Imaging Assembly (AIA) on board Solar Dynamics Observatory (SDO), are analyzed to determine their driving mechanism and physical nature. Two magnetic strands in the localized corona are observed to approach and merge with each other, followed by the generation of brightening, which further propagates in a cusp-shaped magnetic channel. Differential emission measure analysis shows an occurrence of heating in this region of interest. We extrapolate potential magnetic field lines at coronal heights from the observed Helioseismic and Magnetic Imager vector magnetogram via Green’s function method using MPI-AMRVAC. We analyze the field to locate magnetic nulls and quasi-separatrix layers (QSLs), which are preferential locations for magnetic reconnection. Dominant QSLs including a magnetic null are found to exist and match the geometry followed by PDs; therefore, this provides conclusive evidence of magnetic reconnection. In addition, spectroscopic analysis of Interface Region Imaging Spectrograph Si iv λ1393.77 line profiles show a rise of line width in the same time range depicting the presence of mass motion in the observed cusp-shaped region. PDs are observed to exhibit periodicities of around 4 minutes. The speeds of PDs measured by the surfing transform technique are close to each other in four different SDO/AIA bandpasses, i.e., 304, 171, 193, and 131 Å, excluding the interpretation of PDs in terms of slow magnetoacoustic waves. We describe comprehensively the observed PDs as quasiperiodic plasma flows generated as a result of periodic reconnection in the vicinity of a coronal magnetic null.

Self-similar Outflows at the Source of the Fast Solar Wind: A Smoking Gun of Multiscale Impulsive Reconnection?

“…The main factor limiting the accuracy of the ST method is the the nonstationarity of the signal. For quasi-periodic flows such those studied here, the ST uncertainty is typically in the range 2-5 km s −1 (Uritsky et al 2013b;Mondal et al 2023), which is an order of magnitude smaller than the spatial variability of the flow velocity reported in Section 3. Figure 1(d) shows the maximized surfing signal meeting this condition for the time-distance plot in Figure 1(c) at v = 128 km s −1 .…”

“…The region of interest (ROI) covered a 45°limb sector centered at the north pole (Figure 1 Propagating disturbances in each time-distance array were identified using the surfing transform (ST) technique (Uritsky et al 2013b). This technique is designed to identify wave signals in time-distance plots with low signal-to-noise ratios, and it has been used successfully to measure parameters of remotely observed flows and waves (Uritsky et al 2009;Keiling et al 2012;Uritsky et al 2013bUritsky et al , 2021Kumar et al 2022;Raouafi et al 2023a;Mondal et al 2023). The method is based on an analysis of a velocity-dependent surfing signal S(t, u) obtained by averaging the time-distance array along the spatiotemporal defined u, starting from time t. The dynamic range of the signal is maximized when the assumed surfing velocity u matches the true propagation velocity v, in which case the averaging is performed in the reference frame of the propagating disturbance.…”