Hamiltonian kinetic-Hall magnetohydrodynamics with fluid and kinetic ions in the current and pressure coupling schemes

We present two generalized hybrid kinetic-Hall magnetohydrodynamics (MHD) models describing the interaction of a two-fluid bulk plasma, which consists of thermal ions and electrons, with energetic, suprathermal ion populations described by Vlasov dynamics. The dynamics of the thermal components are governed by standard fluid equations in the Hall MHD limit with the electron momentum equation providing an Ohm's law with Hall and electron pressure terms involving a gyrotropic electron pressure tensor. The coupling of the bulk, low-energy plasma with the energetic particle dynamics is accomplished through the current density (current coupling scheme; CCS) and the ion pressure tensor appearing in the momentum equation (pressure coupling scheme; PCS) in the first and the second model, respectively. The CCS is a generalization of two well-known models, because in the limit of vanishing energetic and thermal ion densities, we recover the standard Hall MHD and the hybrid kinetic-ions/fluid-electron model, respectively. This provides us with the capability to study in a continuous manner, the global impact of the energetic particles in a regime extending from vanishing to dominant energetic particle densities. The noncanonical Hamiltonian structures of the CCS and PCS, which can be exploited to study equilibrium and stability properties through the energy-Casimir variational principle, are identified. As a first application here, we derive a generalized Hall MHD Grad–Shafranov–Bernoulli system for translationally symmetric equilibria with anisotropic electron pressure and kinetic effects owing to the presence of energetic particles using the PCS.

A generalization of the Einstein–Maxwell equations

The proposed modifications of the Einstein–Maxwell equations include: (1) the addition of a scalar term to the electromagnetic side of the equation rather than to the gravitational side, (2) the introduction of a four-dimensional, nonlinear electromagnetic constitutive tensor, (3) the addition of curvature terms arising from the non-metric components of a general symmetric connection and (4) the addition of a non-isotropic pressure tensor. The scalar term is defined by the condition that a spherically symmetric particle be force-free and mathematically well behaved everywhere. The constitutive tensor introduces two structure fields: One contributes to the mass and the other contributes to the angular momentum. The additional curvature terms couple both to particle solutions and to localized electromagnetic and gravitational wave solutions. The pressure term is needed for the most general spherically symmetric, static metric. It results in a distinction between the Schwarzschild mass and the inertial mass.

Pressure-tensor method evaluation of the interfacial tension between Gay-Berne isotropic fluid and a smooth repulsive wall

The interfacial properties of confined thermotropic liquid crystalline material {\color{red} are} investigated using {\color{red} the} molecular dynamics simulation technique. The pairwise interaction among {\color{red}the} soft ellipsoidal particles is modeled by...

The Modeling of Interfacial Contacts in Composites Using the Sitting Drop - Solid Body System as an Example

The paper presents an analysis of positions, which a theory of a liquid wetting a solid surface is based on, using the sitting drop equilibrium as an example. Certain inconsistencies are indicated in these positions, which is the subject of the discussion. The paper explains why the interfacial tension of solid-gas has no effect on the equilibrium of a drop. It proposes a mechanism to form a liquid-solid interface layer, the tensor of interfacial tensions of which is represented as a pressure tensor. It is established that the surface tension of the interface layer is variable and changes in magnitude and direction depending on the wetting conditions. It is determined that it is not possible to present a range of phenomena accompanying the wetting of a solid surface with a liquid by examining the equilibrium of a three-phase contact line.

Role of non-diagonal pressure tensor components in balance of magnetopause current sheet

<p>We study the current sheet model separating a strong magnetic field area from the intense solar wind. We use the ideal MHD equations for ideas proposed by D. Nickeler and T. Wiegelmann to describe the transition region with plasma flows inclined to the boundary field. We show that balance in this case can be supported by nondiagonal components of modified pressure tensor. We discuss the possible application of the results to a description of the Earth’s night-side magnetopause boundary and study influence of solar wind characteristics on magnetopause current structure. We show problems that follow from ideal mhd-approach and from our assumptions about stationarity of two-dimensional CS on examples of magnetopause crossings by MMS mission. We speculate about further model development to day-side and magnetopause flanks application. This work is supported by the RFBR grant N 18-02-00218.</p>

Nonideal Electric Field Observed in the Separatrix Region of a Magnetotail Reconnection Event

<p>The microphysics in the separatrix region (SR) plays an important role for the energy conversion in reconnection. Based on the Magnetospheric Multiscale observations in the magnetotail, we present a complete crossing of the current sheet with ongoing magnetic reconnection. The field‐aligned inflowing electrons were observed in both separatrix regions (SRs) and their energy extended up to several times of the thermal energy. Along the SR, a net parallel electrostatic potential was estimated and could be the reason for the inflowing electron streaming. In the northern SR, the electron frozen‐in condition was violated and nonideal electric field was inferred to be caused by the gradient of the electron pressure tensor. The nongyrotropic electron distribution and significant energy dissipation were observed at the same region. The observations indicate that the inner electron diffusion region can extend along the separatrices or some electron‐scale instability can be destabilized in the SR. </p>