In this paper, 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, guide field. The angle θ between magnetic field lines in two half regions is a key parameter in our simulations whereas the initial distribution of the plasma is assumed to be simple; density and pressure are uniform except for the current sheet region. Alfvén waves are generated at the reconnection point and propagate along the reconnected field line. The energy fluxes of the Alfvén waves and magnetoacoustic waves (slow mode and fast mode) generated by the magnetic reconnection are measured. Each flux shows the similar time evolution independent of θ. The percentage of the energies (time integral of energy fluxes) carried by the Alfvén waves and magneto-acoustic waves to the released magnetic energy are calculated. The Alfvén waves carry 38.9%, 36.0%, and 29.5% of the released magnetic energy at the maximum (θ = 80 • ) in the case 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 1 of high-speed solar wind are discussed.

We report the results of three-dimensional magnetohydrodynamic ( MHD) simulations of a jet formation by the interaction between an accretion disk and a large-scale magnetic field. The disk is not treated as a boundary condition but is solved self-consistently. To investigate the stability of the MHD jet, the accretion disk is perturbed with a nonaxisymmetric sinusoidal or random fluctuation of the rotational velocity. The dependences of the jet velocity (v z ), mass outflow rate (Ṁ w ), and mass accretion rate (Ṁ a ) on the initial magnetic field strength in both nonaxisymmetric cases are similar to those in the axisymmetric case. That is, v z / B 1 = 3 0 ,Ṁ w / B 0 , anḋ M a / B 1:4 0 , where B 0 is the initial magnetic field strength. The former two relations are consistent with Michel's steady solution, v z / (B 2 0 /Ṁ w ) 1 = 3 , although the jet and accretion do not reach the steady state. In both perturbation cases, a nonaxisymmetric structure with m ¼ 2 appears in the jet, where m is the azimuthal wavenumber. This structure cannot be explained by Kelvin-Helmholtz instability and seems to originate in the accretion disk. Nonaxisymmetric modes in the jet reach almost constant levels after about 1.5 orbital periods of the accretion disk, while all modes in the accretion disk grow with oscillation. As for the angular momentum transport by Maxwell stress, the vertical component, hB B z /4 i, is comparable to the radial component, hB B r /4 i, in the wide range of initial magnetic field strength.

Distributions of Faraday rotation measure (FRM) and the projected magnetic field derived by a 3-dimensional simulation of MHD jets are investigated based on our "sweeping magnetic twist model". FRM and Stokes parameters were calculated to be compared with radio observations of large scale wiggled AGN jets on kpc scales. We propose that the FRM distribution can be used to discuss the 3-dimensional structure of magnetic field around jets and the validity of existing theoretical models, together with the projected magnetic field derived from Stokes parameters. In the previous paper, we investigated the basic straight part of AGN jets by using the result of a 2-dimensional axisymmetric simulation. The derived FRM distribution has a general tendency to have a gradient across the jet axis, which is due to the toroidal component of the magnetic field generated by the rotation of the accretion disk. In this paper, we consider the wiggled structure of the AGN jets by using the result of a 3-dimensional simulation. Our numerical results show that the distributions of FRM and the projected magnetic field have a clear correlation with the large scale structure of the jet itself, namely, 3-dimensional helix. Distributions, seeing the jet from a certain direction, show a good matching with those in a part of 3C449 jet. This suggests that the jet has a helical structure and that the magnetic field (especially the toroidal component) plays an important role in the dynamics of the wiggle formation because it is due to a current-driven helical kink instability in our model.

Using the numerical data of MHD simulation for AGN jets based on our "sweeping magnetic twist model", we calculated the Faraday rotation measure (FRM) and the Stokes parameters to compare with observations. We propose that the FRM distribution can be used to discuss the 3-dimensional structure of magnetic field around jets, together with the projected magnetic field derived from the Stokes parameters. In the present paper, we supposed the basic straight part of AGN jet, and used the data of axisymmetric simulation. The FRM distribution we derived has a general tendency to have gradient across the jet axis, which is due to the toroidal component of the helical magnetic field generated by the rotation of the accretion disk. This kind of gradient in the FRM distribution is actually observed in some AGN jets (e.g. Asada et al. 2002), which suggests helical magnetic field around the jets and thus supports our MHD model. Following this success, we are now extending our numerical observation to the wiggled part of the jets using the data of 3-dimensional simulation based on our model in the following paper.