ar X iv : a st ro - p h / 98 04 16 6 v 1 1 6 A pr 1 99 8 Reconnection via the Tearing Instability

We discuss the role of tearing instabilities in magnetic reconnection. In three dimensions this instability leads to the formation of strong Alfvenic waves that remove plasma efficiently from the reconnection layer. As a result the instability proceeds at high rates while staying close to the linear regime. Our calculations show that for a resistive fluid the reconnection speed scales as VARe , where VA is the Alfven velocity and Re is the magnetic Reynolds number. In the limit of vanishing resistivity, tearing modes proceed at a non-zero rate, driven by the electron inertia term, giving rise to a reconnection speed ∼ VA(c/ωpLx) , where ωp is the plasma frequency and Lx is the transverse scale of the reconnection layer. Formally this solves the problem of fast reconnection, but in practice this reconnection speed is small. Subject headings: Magnetic fields; Galaxies: magnetic fields, ISM: molecular clouds, magnetic fields