Akash Bairagi | Searcharxiv

arXiv2026

Interaction of Fast Magnetoacoustic Wave with the Localized Coronal Null and Generation of the Energetic Alfv\'en Wave Packet

In the present paper, we have performed 2.5D resistive magnetohydrodynamic simulations of the interaction of a fast magnetoacoustic wave with a localized coronal magnetic null point. As a result, an Alfv\'en wave packet is generated by the mode conversion when a fast magnetoacoustic perturbation interacts with the null point. The field-aligned plasma flows are also generated due to the non-linear effects. When the fast mode wavefront interacts with the null, some parts of this wavefront get refracted around it, while some other part is trapped at the null region. Subsequently, the velocity fluctuation out of the plane and in-phase magnetic field fluctuations have evolved and propagated with the local Alfv\'en speed along the separatrixes at one side of the coronal null region. The resulting disturbance behaves as an incompressible and energetic Alfv\'en wave packet. A secondary fast magnetoacoustic wave is also produced and propagates. In the synthetic SDO/AIA observations, no intensity fluctuations are evident in the region where the Alfv\'en wave packet propagates, while the fast magnetoacoustic wave fronts are clearly evident. Our results suggest that given the appropriate physical conditions at the null, when the fast mode wave is incident, Alfv\'en packets can be excited due to the mode conversion, further carrying substantial momentum and energy flux in the solar corona.

astro-ph.SR↗

arXiv2024

Dynamics and Energetics of Resistive, Thermally Conductive, and Radiative Plasma in Coronal Current Sheets due to Asymmetric External Perturbation

We study the asymmetric interaction of wave-like velocity perturbation with a coronal current sheet (CS) in the presence of resistivity, thermal conduction (TC) and radiative cooling (RC). We analyze the dynamics and energetics of CS in four cases, namely, (i) no energy loss, (ii) TC only, (iii) RC only and, (iv) TC+RC. Before fragmentation, thinning and elongation of the CS are found to be identical in all four cases and therefore independent of presence or absence of energy loss effects. Onset times, corresponding Lundquist numbers and aspect ratios suggest that TC advances the onset of fragmentation while RC has the opposite effect in comparison to absence of energy losses. Reconnection takes place at a higher rate in presence of TC and TC+RC in the tearing unstable CS. The speed of plasmoids are also found to be higher under the effect of TC and TC+RC. In presence of TC and TC+RC, average density becomes higher within the tearing unstable CS than in other two cases. As expected, estimated average temperature is increasing with highest and lowest rate in absence of energy losses and in presence of both TC and RC respectively. After the onset of fragmentation, the rate of decrement of average magnetic energy density and increment of average kinetic energy density becomes higher in presence of TC and TC+RC than in other two cases. Thus we conclude that presence of energy loss mechanisms critically influence the dynamics, energetics, and plasmoid formation within a reconnecting coronal CS.

astro-ph.SR↗