Magnetic Reconnection Induced by Convective Intensification of Solar Photospheric Magnetic Fields

We investigate photospheric magnetic reconnection induced by convective intensificd ..ation of solar surface magnetic fields, performing 2.5-dimensional magnetohydrodynamic (MHD) numerical simulations. We assume as the initial conditions oppositely directed vertical weak magnetic fields ( B z ) penetrating a convectively unstable layer. To initiate convective instability, the unstable layer is perturbed by weak circular motions. As a result of the growing convective motions, the oppositely directed magnetic fields are swept up into the convective downflow region, forming a current sheet between them. At the same time, the field strength is increased to kilogauss range, and the current density in the current sheet is strengthened. As a result, magnetic reconnection is initiated. It is shown that upward-propagating slow-mode MHD waves are generated by a collision of a reconnection jet with U-shaped field lines. Moreover, when the initial magnetic fields are not parallel, i.e., when there is a perpendicular component of the magnetic field ( B y = B z ) in the other half of the flux sheet, Alfvén waves are also generated as a result of reconnection. The energy flux carried by the slow and Alfvén waves are 10 10 and 10 9 ergs cm -2 s -1 and the durations are 80 and 100 s, respectively, at the photosphere. The energies of these waves are sufficient to produce solar spicules. Thus, photospheric magnetic reconnection might be one of the causes of solar spicules.