  Based on the first principles (i.e. (i) by balancing the magnetic field
advection with the term containing electron pressure tensor non-gyrotropic
components in the generalised Ohm's law; (ii) using the conservation of mass;
and (iii) assuming that the weak magnetic field region width, where electron
meandering motion supports electron pressure tensor off-diagonal
(non-gyrotropic) components, is of the order of electron Larmor radius) a
simple model of magnetic reconnection in a collisionless regime is formulated.
The model is general, resembling its collisional Sweet-Parker analogue in that
it is not specific to any initial configuration e.g. Harris type tearing
unstable current sheet, X-point collapse or otherwise. In addition to its
importance from the fundamental point of view, the collisionless reconnection
model offers a much faster reconnection rate (M_c'less=(c/omega_pe)^2 /(r_L,e
L)) than Sweet-Parker's classical one (M_sp=S^-1/2). The width of the diffusion
region (current sheet) in the collisionless regime is found to be
delta_c'less=(c/omega_pe)^2/r_L,e, which is independent of global reconnection
scale L and is only prescribed by micro-physics (electron inertial length,
c/omega_pe, and electron Larmor radius, r_L,e). Amongst other issues, the
fastness of the reconnection rate alleviates e.g. the problem of interpretation
of solar flares by means of reconnection, as for the typical solar coronal
parameters the obtained collisionless reconnection time can be a few minutes,
as opposed to Sweet-Parker's equivalent value of < a day. The new theoretical
reconnection rate is compared to the MRX device experimental data by [Yamada et
al., Phys. Plasmas, 13, 052119 (2006), Ji et al. GRL, 35, 13106 (2008)] and a
good agreement is obtained.
