3,157 research outputs found
Spontaneous transition to a fast 3D turbulent reconnection regime
We show how the conversion of magnetic field energy via magnetic reconnection
can progress in a fully three-dimensional, fast, volume-filling regime. An
initial configuration representative of many laboratory, space and
astrophysical plasmas spontaneously evolves from the well-known regime of slow,
resistive reconnection to a new regime that allows to explain the rates of
energy transfer observed in jets emitted from accretion disks, in stellar/solar
flare processes as well as in laboratory plasmas. This process does not require
any pre-existing turbulence seed which often is not observed in the host
systems prior to the onset of the energy conversion. The dynamics critically
depends on the interplay of perturbations developing along the magnetic field
lines and across them, a process possible only in three-dimensions. The
simulations presented here are the first able to show this transition in a
fully three-dimensional configuration.Comment: 6 pages, 6 figure
Magnetic domain wall motion in a nanowire: depinning and creep
The domain wall motion in a magnetic nanowire is examined theoretically in
the regime where the domain wall driving force is weak and its competition
against disorders is assisted by thermal agitations. Two types of driving
forces are considered; magnetic field and current. While the field induces the
domain wall motion through the Zeeman energy, the current induces the domain
wall motion by generating the spin transfer torque, of which effects in this
regime remain controversial. The spin transfer torque has two mutually
orthogonal vector components, the adiabatic spin transfer torque and the
nonadiabatic spin transfer torque. We investigate separate effects of the two
components on the domain wall depinning rate in one-dimensional systems and on
the domain wall creep velocity in two-dimensional systems, both below the
Walker breakdown threshold. In addition to the leading order contribution
coming from the field and/or the nonadiabatic spin transfer torque, we find
that the adiabatic spin transfer torque generates corrections, which can be of
relevance for an unambiguous analysis of experimental results. For instance, it
is demonstrated that the neglect of the corrections in experimental analysis
may lead to incorrect evaluation of the nonadiabaticity parameter. Effects of
the Rashba spin-orbit coupling on the domain wall motion are also analyzed.Comment: 14 pages, 3 figure
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