Generation of Alfvén waves by magnetic reconnection

Abstract

In this paper, the results of 2.5-dimensional magnetohydrodynamical simulations are reported for the magnetic reconnection of non-perfectly antiparallel magnetic fields. The magnetic field has a component perpendicular to the computational plane, that is, a guide field. The angle θ between the magnetic field lines in two half regions was a key parameter in our simulations, whereas the initial distribution of the plasma was assumed to be simple; the density and pressure were uniform, except for the current sheet region. Alfvén waves were generated at the reconnection point and propagated along the reconnected field line. The energy fluxes of the Alfvén waves and the magnetoacoustic waves (slow mode and fast mode) generated by magnetic reconnection were measured. Each flux shows a similar time evolution independent of θ. The percentages of the energies (time integral of energy fluxes) carried by the Alfvén waves and magneto-acoustic waves to the released magnetic energy were calculated. The Alfvén waves carry 38.9%, 36.0%, and 29.5% of the released magnetic energy at the maximum (θ = 80°) in the cases of β = 0.1, 1, and 20, respectively, where β is the plasma β (the ratio of gas pressure to magnetic pressure). The magneto-acoustic waves carry 16.2% (θ = 70°), 25.9% (θ = 60°), and 75.0% (θ = 180°) of the energy at the maximum. Implications of these results for solar coronal heating and acceleration of high-speed solar wind are discussed. © 2010. Astronomical Society of Japan.