Collapsing magnetic instability to solar intermittent flux and anomalous viscosity in accretion disks

Abstract

Abstract. It is shown that the transverse plasmon field is modulationally unstable in the Lyapunov sense, leading to a self-similar collapse of the magnetic flux. Such a collapsing magnetic instability is analyzed in both cases of magnetohydrodynamics and kinetic plasma physics, with their applications to solar intermittent flux and anomalous viscosity in accretion disks, respectively. In the first case, we find that the equilibrium between the ponderomotive force and the Lorentz force in a current sheet gives rise to a more spatially intermittent collapsing magnetic flux, very similar to a turbulent pattern; as a result, the 0.1 kG flux cells with larger scales emerging at the surface from the solar interior become shredded and the flux is thereby contracted rather quickly to a small scale of the order of 100 km as well as concentrated into a 1-2 kG state. In the second case, based on Vlasov equations and Maxwell equations, the collapsing feature of the self-generated magnetic field from transverse plasmons is investigated on rather small scales of the motion or electric current in accretion disks; as the effects of the intermittent magnetic flux, an anomalous magnetic viscosity and an anomalous resistivity are indicated, with a different magnetic Prandtl number, which is not very sensitive to the temperature T .

Self-similar collapse in a circular magnetic field and electron jets by hybrid transverse plasmon

“…Li et al has estimated the anomalous dc resistivity and viscosity in accretion disks from the selfgenerated spatially intermittent magnetic flux by the selfsimilar solution. 34) In much the same sense, we will estimate the velocity of the electron jet through the self-similar solution.…”

Strong Langmuir turbulence in Kappa distributed plasmas

“…Thus, the waves and instabilities in Kappa distributed plasmas are investigated using kinetic theory based on the Vlasov-Maxwell system in previous works mentioned above. And on the other hand, although for the Maxwellian plasma in strong turbulence regime, the growth rate of plasmons is often much larger than the electron collision frequency, [45][46][47] hence, it is reasonable to omit the collision term in the kinetic equation. Starting from the Vlasov equations,…”

Structure and stability of a thin protostar disk with anomalous viscosity

“…In this section, we briefly introduce the calculation processes of the magnetic kinematic viscosity which has been done by Li and Zhang (for detail, see Li and Zhang 2002). It is analytically proved that the self-generated magnetic fields in accretion disks show selfcollapse behavior (Li and Ma 1994).…”

“…A recent work (Li and Zhang 2002) has shown that the magnetic fields self-generated by the transverse plasmons are modulationally unstable in the Lyapunov sense, leading to a self-similar collapse of the magnetic flux and resulting in local magnetic structures. Highly spatially intermittent flux is responsible for generating the anomalous viscosity.…”

“…It is worth noted that magnetic field plays an important role in many fields of astrophysics, but the normal macroscopic magnetic field in accretion disks are much smaller than the self-generated magnetic fields which are responsible for generating the anomalous viscosity (Li and Zhang 2002). Therefore, in this paper, we will calculate numerically the structure of a thin protostar disk and perform a general analysis of the stability with anomalous magnetic viscosity, but the background field is not included.…”