Search

The aim of this paper is to demonstrate the possible use of the new coronal model COCONUT to compute a detailed representation of a numerical CME at 0.1~AU, after its injection at the solar surface and propagation in a realistic solar wind, as derived from observed magnetograms. We present the implementation and propagation of modified Titov-D\'emoulin (TDm) flux ropes in the COCONUT 3D MHD coronal model. The background solar wind is reconstructed in order to model two opposite configurations representing a solar activity maximum and minimum respectively. Both were derived from magnetograms which were obtained by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamic Observatory (SDO) satellite. We track the propagation of 24 flux ropes, which differ only by their initial magnetic flux. We especially investigate the geometry of the flux rope during the early stages of the propagation as well as the influence of its initial parameters and solar wind configuration on 1D profiles derived at 0.1~AU. At the beginning of the propagation, the shape of the flux ropes varies between simulations during low and high solar activity. We find dynamics that are consistent with the standard CME model, such as the pinching of the legs and the appearance of post-flare loops. Despite the differences in geometry, the synthetic density and magnetic field time profiles at 0.1~AU are very similar in both solar wind configurations. These profiles are similar to those observed further in the heliosphere and suggest the presence of a magnetic ejecta composed of the initially implemented flux rope and a sheath ahead of it. Finally, we uncover relationships between the properties of the magnetic ejecta, such as density or speed and the initial magnetic flux of our flux ropes., Comment: 20 pages, 13 figures

We present a new insight into the propagation, attenuation and dissipation of two-fluid, torsional Alfv\'en waves in the context of heating of the lower solar atmosphere. By means of numerical simulations of the partially-ionized plasma, we solve the set of two-fluid equations for ion plus electron and neutral fluids in three-dimensional (3D) Cartesian geometry. We implement initially a current-free magnetic field configuration, corresponding to a magnetic flux-tube that is rooted in the solar photosphere and expands into the chromosphere and corona. We put the lower boundary of our simulation region in the low chromosphere, where ions and neutrals begin to decouple, and implement there a monochromatic driver that directly generates Alfv\'en waves with a wave period of 30 s. As the ion-neutral drift increases with height, the two-fluid effects become more significant and the energy carried by both Alfv\'en and magneto-acoustic waves can be thermalized in the process of ion-neutral collisions there. In fact, we observe a significant increase in plasma temperature along the magnetic flux-tube. In conclusion, the two-fluid torsional Alfv\'en waves can potentially play a role in the heating of the solar chromosphere., Comment: 10 pages, 7 figures

With the use of our JOANNA code, which solves radiative equations for ion + electron and neutral fluids, we perform realistic 2.5D numerical simulations of plasma outflows associated with the solar granulation. These outflows exhibit physical quantities consistent to the order of magnitude with the observational findings for mass and energy losses in the upper chromosphere, transition region and inner corona, and they may originate the fast solar wind.

Using high-resolution numerical simulations we investigate the plasma heating driven by periodic two-fluid acoustic waves that originate at the bottom of the photosphere and propagate into the gravitationally stratified and partially ionized solar atmosphere. We consider ions+electrons and neutrals as separate fluids that interact between themselves via collision forces. The latter play an important role in the chromosphere, leading to significant damping of short-period waves. Long-period waves do not essentially alter the photospheric temperatures, but they exhibit the capability of depositing a part of their energy in the chromosphere. This results in up about a five times increase of ion temperature that takes place there on a time-scale of a few minutes. The most effective heating corresponds to waveperiods within the range of about 30-200 s with a peak value located at 80 s. However, we conclude that for the amplitude of the driver chosen to be equal to 0.1 km s$^{-1}$, this heating is too low to balance the radiative losses in the chromosphere.

We perform numerical simulations of impulsively generated magnetic swirls in an isolated flux tube which is rooted in the solar photosphere. These swirls are triggered by an initial pulse in a horizontal component of the velocity. The initial pulse is launched either: (a) centrally, within the localized magnetic flux tube; or (b) off-central, in the ambient medium. The evolution and dynamics of the flux tube is described by three-dimensional, ideal magnetohydrodynamic equations. These equations are numerically solved to reveal that in case (a) dipole-like swirls associated with the fast magnetoacoustic kink and $m=1$ Alfv\'en waves are generated. In case (b), the fast magnetoacoustic kink and $m=0$ Alfv\'en modes are excited. In both these cases, the excited fast magnetoacoustic kink and Alfv\'en waves consist of similar flow pattern and magnetic shells are also generated with clockwise and counter-clockwise rotating plasma within them, which can be the proxy of dipole-shaped chromospheric swirls. The complex dynamics of vortices and wave perturbations reveals the channelling of sufficient amount of energy to fulfill energy losses in the chromosphere ($\sim$ 10$^{4}$ W m$^{-1}$) and in the corona ($\sim$ 10$^{2}$ W m$^{-1}$). Some of these numerical findings are reminiscent of signatures in recent observational data.

We study non-linear surjective mappings on subsets of ${\cal M}_n(F)$, which preserve the zeros of some fixed polynomials in noncommuting variables. Keywords: Matrix algebra, Multilinear polynomials, Preservers., Comment: 33 pages