We describe and analyze a model for time-varying, localized reconnection in a current sheet with skewed magnetic field orientations on opposite sides. As in Petschek's description, disruption is initiated in a localized part of the current sheet known as the diffusion region, and the disturbances are subsequently propagated into the system at large through magnetohydrodynamlc (MHD) Waves. The MHD waves therefore play the do•ninant role in energy conversion, and collectively they form an outflow for plasma streaming toward the current sheet and a field reversal region joining magnetic field lines from opposite sides. We restrict the analysis to an incompressible plasma, in which case the Affv•n wave and the slow shock merge to form shocks bounding the field reversal or outflow region, and to the case of weak reconnection, which implies that the reconnection electric field is much smaller than the product of the characteristic values of the external field strength and Affv•n speed. It is then possible to perform a perturbation analysis of the MHD equations wlfich govern the plasma and field behavior. The analysis can be formulated as a •nixture of three well-known problems. The problem of determining the appropriate combination of MHD waves corresponds to the Riemann problem, Which also specifies the tangential field and flow components in the field reversal region. These results, it is important to note, are not sensitive to variations in the reco•mection rate. Reconnection also acts as a source of surface waves, and their analysis deternxines the behavior of the perpendicular field and flow components and the shape of the shocks. Lastly, the field reversal region can be considered as a thin boundary layer in our treatment, and the external disturbances can therefore be solved in a way similar to the flow around a thin aerofoil. The model presented here can be applied to the Earth's magnetopause, where recom•ection is considered to be the dominant process coupling the solar wind and the magnetosphere. In particular, the results can be used to interpret different manifestations of ß recotmection such as accelerated i•lasma flows along the magnetopause and flux transfer e•ents. 1. INTRODUCTION Magnetic field line reconnection is a universal energy con? version process in space plasmas [e.g., Vasyliunas, 1975; Hones, 1984; Pudovkin and Seinenov, 1985; Priest, 1985]. It is usually described in terms of magnetic field lines. In this case we can visualize reconnection as a process which "cuts"magnetic field lines and subsequently "connects"the different ends to field lines of different topological origin. An alternative description is in terms of electric currents [Seinenov et al., 1983; Pudovkin and Seinenov, 1985; Biernat et al., 1987]. In this description, reconnection is a process which changes and reorganizes the geometry of a current system. These two descriptions are fully compatible with each other; and in particular the Alfv6n wave, which acts as the carrier of current in a plasma, provides a linking concept. D...

No abstract

The variations of the plasma parameters and of the magnetic field in the vicinity of the stream line passing the subsolar point at the magnetopause are calculated by using a special flow pattern of the plasma which is the result of the formation of a stagnation line at the nose part of the magnetopause. The calculations indicate a rotation of the direction of the magnetic field across the magnetosheath. The displacement of the magnetopause due to the penetration of the solar wind magnetic field into the magnetosphere is discussed.

Parameters of the solar wind plasma and magnetic field in the magnetosheath are calculated for an anisotropic plasma model in the Chew–Goldberger–Low approximation. It is shown that in the case when the energy transfer between the perpendicular and parallel (with respect to the magnetic field) degrees of freedom is absent, the resulting temperature anisotropy may significantly affect the plasma density and magnetic field intensity profiles across the magnetosheath. However, in this case, the value of the temperature anisotropy (the ratio of the perpendicular to the parallel component of the temperature with respect to the magnetic field, T⊥/T‖) becomes unrealistic high. To bring agreement between the model values of the temperature anisotropy and experimental data, the existence of an intensive proton pitch-angle diffusion is assumed. In the case when the temperature anisotropy relaxation time is much smaller than the time taken by the solar wind plasma to move from the bow shock to the magnetopause, one has T⊥/T‖≈1, and the profiles of the magnetic field and plasma density along the subsolar stream line insignificantly differ from the profiles obtained for the isotropic magnetohydrodynamic (MHD) model. In an intermediate case when the relaxation time is of the order of the plasma transport time, the value of T⊥/T‖ may amount to the values observed in the magnetosheath.