MHD-shock structures of astrospheres: λ Cephei -like astrospheres

Abstract

The interpretation of recent observations of bow shocks around O-stars and the creation of corresponding models require a detailed understanding of the associated (magneto-)hydrodynamic structures. We base our study on three-dimensional numerical (magneto-)hydrodynamical models, which are analyzed using the dynamically relevant parameters, in particular, the (magneto)sonic Mach numbers. The analytic Rankine-Hugoniot relation for HD and MHD are compared with those obtained by the numerical model. In that context we also show that the only distance which can be approximately determined is that of the termination shock, if it is a hydrodynamical shock. For MHD shocks the stagnation point does not, in general, lie on the inflow line, which is the line parallel to the inflow vector and passing through the star. Thus an estimate via the Bernoulli equation as in the HD case is, in general, not possible. We also show that in O-star astrospheres, distinct regions exist in which the fast, slow, Alfvénic, and sonic Mach numbers become lower than one, implying sub-slow magnetosonic as well as sub-fast and sub-sonic flows. Nevertheless, the analytic MHD Rankine Hugoniot relations can be used for further studies of turbulence and cosmic ray modulation.

Biomolecules as Model Indicators of In Vitro and In Vivo Cold Plasma Safety

“…Thus, for successful application of cold plasma technology it is important to not only understand interactions at the bio-plasma interface during treatment, but also to understand the short-term and long-term consequences of plasma induced biomolecule alteration and the effect this may have on biochemical processes. In fact, plasma induced chemical modification of proteins and amino acids [19,20] and lipids [21] have been studied in isolation. Additionally, both simulated, modeling studies and direct experimentation have shown how interactions of cold plasma chemical species modify amino acids [22,23], change protein structure and function [19,[24][25][26] and oxidize lipids [27,28] but these studies are limited in their ability to examine or understand the long-term biological effects of the plasma induced modifications in a complex biosystem.…”

Lorentzian Entropies and Olbert's κ - Distribution

“…Such correlations are implicit to the index κ and indicate strong nonlinear couplings, which are provided by interaction potentials which are mediated not by collisions but by excitation of waves. It is thus not surprising if κ-distributions are found in turbulent dilute high temperature plasmas like the solar wind [28], near collisionless shock waves [29], Earth's bow shock [30], the magnetosheath [31], at the boundaries of the heliosphere and astrospheres [32], where various types of waves can be excited as both, eigenmodes or sidebands, which even occupy the evanescent branches of the dielectric response function causing a continuous almost featureless power spectrum of fluctuations, which is typical for well-developed turbulence. One may, therefore, expect that the statistical mechanics underlying well-developed collisionless turbulence will become kind of Olbert-Lorentzian in terms of the probability distribution.…”

The ablation of gas clouds by blazar jets

“…However, we can use the known density structure of astrospheres, which is similar to the hydrostatic case. From some distance r s,0 above the star's surface up to the termination shock, the density follows an inverse-square law (e.g., Scherer et al 2020). Following our deliberations in Sect.…”