No abstract

Context. Magnetohydrodynamic (MHD) waves have significant potential as a plasma heating mechanism. Finding a suitable wave dissipation mechanism is a very tough task, given the many observational constraints on the models, and this has resulted in the development of an important research community in solar physics. The magnetic field structure has an important role in the solar corona heating. Here, we investigate in detail current sheet mode generation via magnetic reconnection and mode conversion releases some of the free magnetic energy and produces heating. In addition, energy conversion is discussed completely. Moreover, nonlinear effects on density variations and, in turn, mode conversion are pursued. Aims. In order to assess the role of magnetoacoustic waves in plasma heating, we have modeled in detail a fast magneto-acoustic wave pulse near a magnetic null-point in a finite plasma-β. The behavior of the propagation and dissipation of the fast magneto-acoustic wave is investigated in the inhomogeneous magnetically structured solar corona. Particular attention is given to the dissipation of waves and coronal heating and energy transfer in the solar corona, focusing on the energy transfer resulting from the interaction of fast magneto-acoustic waves with 2.5D magnetic null-points. Methods. The shock−capturing Godunov−type PLUTO code was used to solve the ideal MHD set of equations in the context of wave-plasma energy transfer. Results. It is shown that magneto-acoustic waves could be a viable candidate to contribute significantly to the heating of the solar corona and maintain the solar corona at a temperature of a few million degrees. The temperature is not constant in the corona. Coronal heating occurs near magnetic null points. It is found that magnetic reconnection, phase mixing and mode conversion contribute to the heating. Moreover, nonlinear fast and slow magnetoacoustic waves are decoupled except in β = 1 layer.

We performed a numerical study for interpreting observations of plasma blobs occurring in the solar corona. Considering all of the previous studies and the presence of magnetic null points together with propagating MHD waves in the solar corona, we guessed that the interaction of fast magnetoacoustic waves with null points could give rise to blobs under coronal conditions. The outcome of these interactions contributes to coronal jets and flares which directly affects us on Earth. The propagation of magnetoacoustic waves in the vicinity of a magnetic null point contributes to the high current density accumulation at the small scale around the magnetic null point which has significant magnetic gradients. When nonlinearity gets dominant, the variation of current density could result in instabilities and thus anomalous resistivity. Moreover, it is demonstrated that plasmoids with eruption events take place in the solar corona without considering the transition region. In our numerical simulation results, it is interesting that plasma blobs manifest themselves in many parameters including current density, temperature, plasma density, flows and magnetic fields simultaneously, and consistent with the generation of plasmoids. In this work, it is found that plasmoid instability is the reason of the plasma blobs and tiny blobs are produced by the tearing instability occurring in thin current sheets.

The aim of the present study is to provide insight on the induced compressive perturbations together with the modifications of the environmental parameters in the course of Alfvén wave interaction with a solar magnetic null-point. The shock-capturing Godunov-type code PLUTO is used to solve the set of ideal magnetohydrodynamic equations. The nonlinear effects connected with an initial Alfvén pulse nearing a magnetic null point induces fast and slow magnetoacoustic waves with anti phase conduct. The induced current density and flows are independent of the local plasma-$$\beta$$ β at the reconnection site. The induced inflows and outflows highly depend on the polarization. The inflows have a stronger effect compared to the outflows in both the x and y directions showing its peak in the x-direction. The dominant wave that couples to flows is the fast wave due to the in-phase harmony between perturbations of the compressive parameters and the fast wave. The induced current density possesses a steady orientation at the reconnection site which governs the diffusion or propagation of the waves. Induced perturbations by the nonlinear forces together with their back reaction on the Alfvén wave have a significant role in the current density excitation being responsible for the creation of inflows and outflows that are possible candidates for the creation of solar jets which has a significant contribution towards coronal seismology.