arXiv subjects

Anton Nechaev

Publications and source records attributed to Anton Nechaev.

3 recordsLinked to original sources

arXiv2023

Turbulent multicomponent magnetopause: Analytical description and kinetic simulation of complex distributed current sheets

We carry out particle-in-cell simulations of complex current sheets of the family of analytically found Vlasov--Maxwell equilibria that model a collisionless magnetopause and allow for arbitrary energy distributions and countercurrents of various particle component. We find that, depending on the parameters, i)~a weak small-scale bending-type instability is always present at the sharp low-density plasma boundary of such a magnetopause, and ii)~the development of a small-scale Weibel-type instability inside a magnetopause is either excluded or possible. Both cases are studied and compared for two variants of the particle energy distribution~ -- Maxwellian and Kappa. The long-term stability of the whole current sheet is observed either without or with saturated Weibel-type turbulence, which can be generated in a low-magnetized region between neighboring countercurrents. We point out the applicability of the developed model of distributed current sheets and the results of analysis of their small-scale instability for the description of physical phenomena in the magnetopauses of planets and late-type stars.

physics.plasm-ph↗

arXiv2023

Electron Weibel instability and~quasi-magnetostatic structures in~an~expanding collisionless plasma

We outline transient quasi-magnetostatic phenomena associated with Weibel-type instabilities, mainly, the formation and decay of the current sheets and filaments. We consider a collisionless anisotropic plasma cloud with hot electrons expanding into an inhomogeneous background plasma taking into account an external magnetic field in different geometries entailing (i) a hot-electron spot of a circular or cylindrical form within an initial-value problem or a finite-time injection of electrons from a target surface, (ii) inhomogeneous layers of cold background plasma of different densities and spatial scales, (iii) an external magnetic field with three orientations: perpendicular to the target or along it, directed either across or parallel to a long axis of the hot-electron spot. We heed typical laser-plasma experiments. We outline development of the principle current structures linked with distinct forms of the anisotropic electron velocity distribution using particle-in-cell modeling of the instability process for diverse sets of the attributes (i)--(iii). Applications to the analysis of laboratory and space plasma problems involving an explosive development of the small-scale filamentation of the electric current and self-consistent magnetic turbulence are discussed.

physics.plasm-ph↗

arXiv2021

Multi-scale magnetic field structures in an expanding elongated plasma cloud with hot electrons subject to an external magnetic field

We carry out 3D and 2D PIC-simulations of the expansion of a magnetized plasma that initially uniformly fills a half-space and contains a semi-cylindrical region of heated electrons elongated along the surface of the plasma boundary. This geometry is related, for instance, to the ablation of a plane target by a femtosecond laser beam under quasi-cylindrical focusing. We find that the decay of the inhomogeneous plasma--vacuum discontinuity is strongly affected by an external magnetic field parallel to its boundary. We observe various transient phenomena, including the anisotropic scattering of electrons and the accompanying Weibel instability, and reveal various spatial structures of the arising magnetic field and current, including multiple flying apart filaments of a z-pinch type and slowly evolving current sheets with different orientations. The magnitude of the self-generated magnetic field can be of the order of or significantly exceed that of the external one. Such phenomena are expected in the laser and cosmic plasmas, including the explosive processes in the planetary magnetospheres and stellar coronal arches.

physics.plasm-ph↗