We present results from three-dimensional (3-D) numerical simulations investigating the magnetohydrodynamics of cloud-wind interactions. The initial cloud is spherical while the magnetic field is uniform and transverse to the cloud motion. A simplified analytical model that describes the magnetic energy evolution in front of the cloud is developed and compared with simulation results. In additi...

We present the results of 2.5-dimensional resistive magnetohydrodynamic (MHD) simulations of the magnetic interaction between a weakly magnetized neutron star and its accretion disk. General relativistic effects are simulated by using the pseudo-Newtonian potential. We find that well-collimated jets traveling along the rotation axis of the disk are formed by the following mechanism: (1) The mag...

We propose a model of hard X-ray flares in protostars observed by ASCA satellite. Assuming that the dipole magnetic field of the protostar threads the protostellar disk, we carried out 2.5-dimensional magnetohydrodynamic (MHD) simulations of the disk-star interaction. The closed magnetic loops connecting the central star and the disk are twisted by the rotation of the disk. As the twist accumul...

virial theorem is important for understanding stellar structures. it produces an interesting connection between magnetic and gravitational energies. using the general form of the virial theorem including the magnetic field (toroidal magnetic field), we may explain the solar dynamo model in relation to variations of the magnetic and gravitational energies. we emphasize the role of the gravitatio...

Magnetic reconnection has been established as the dominant mechanism by which magnetic fields in different regions change topology to create open magnetic field lines that allow energy and momentum to flow into the magnetosphere. One of the persistent problems of magnetic reconnection is the question of whether the process is continuous or intermittent and what input condition(s) might favor on...

Reconnection is the process by which magnetic fields in a conducting fluid change their topology. This process is essential for understanding a wide variety of astrophysical processes, including stellar and galactic dynamos and astrophysical turbulence. To account for solar flares, solar cycles, and the structure of the galactic magnetic field, reconnection must be fast, propagating with a spee...

Magnetic reconnection may play an important role in heating the corona through a release of magnetic energy. An understanding of how reconnection proceeds can contribute to explaining the observed behavior. Here, recent theoretical work on magnetic reconnection for coronal conditions is reviewed. Topics include the rate that collisionless (Hall) reconnection proceeds, the conditions under which...

Aims. To investigate magnetic reconnection rates during the coalescence of two current loops in the solar chromosphere, by altering the neutralhydrogen to proton density ratio, ioniziation/recombination coefficients, collision frequency and relative helicity of the loops. Methods. 2.5D numerical simulations of the chromosphere were conducted using a newly developed two-fluid (ion-neutral) numer...

We conduct comprehensive analysis of an X2.0 flare to derive quantities indicative of magnetic reconnection in solar corona by following temporally and spatially resolved flare ribbon evolution in the lower atmosphere. The analysis reveals a macroscopically distinctive two-stage reconnection (Moore et al. 2001) marked by a clear division in morphological evolution, reconnection rate, and energy...