arXiv subjects

I. F. Shaikhislamov

Publications and source records attributed to I. F. Shaikhislamov.

21 records · Page 2Linked to original sources

arXiv2017

Two regimes of interaction of a Hot Jupiter's escaping atmosphere with the stellar wind and generation of energized atomic hydrogen corona

The interaction of escaping upper atmosphere of a hydrogen rich non-magnetized analog of HD209458b with a stellar wind of its host G-type star at different orbital distances is simulated with a 2D axisymmetric multi-fluid hydrodynamic model. A realistic sun-like spectrum of XUV radiation which ionizes and heats the planetary atmosphere, hydrogen photo-chemistry, as well as stellar-planetary tidal interaction are taken into account to generate self-consistently an atmospheric hydrodynamic outflow. Two different regimes of the planetary and stellar winds interaction have been modelled. These are: 1) the "captured by the star" regime, when the tidal force and pressure gradient drive the planetary material beyond the Roche lobe towards the star, and 2) the "blown by the wind" regime, when sufficiently strong stellar wind confines the escaping planetary atmosphere and channels it into the tail. The model simulates in details the hydrodynamic interaction between the planetary atoms, protons and the stellar wind, as well as the production of energetic neutral atoms (ENAs) around the planet due to charge-exchange between planetary atoms and stellar protons. The revealed location and shape of the ENA cloud either as a paraboloid shell between ionopause and bowshock (for the "blown by the wind" regime), or a turbulent layer at the contact boundary between the planetary stream and stellar wind (for the "captured by the star" regime) are of importance for the interpretation of Lyα absorption features in exoplanetary transit spectra and characterization of the plasma environments.

astro-ph.EP↗

arXiv2015

Atmosphere expansion and mass loss of close-orbit giant exoplanets heated by stellar XUV: I. Modeling of hydrodynamic escape of upper atmospheric material

In the present series of papers we propose a consistent description of the mass loss process. To study the effects of intrinsic magnetic field of a close-orbit giant exoplanet (so-called Hot Jupiter) on the atmospheric material escape and formation of planetary inner magnetosphere in a comprehensive way, we start with a hydrodynamic model of an upper atmosphere expansion presented in this paper. While considering a simple hydrogen atmosphere model, we focus on selfconsistent inclusion of the effects of radiative heating and ionization of the atmospheric gas with its consequent expansion in the outer space. Primary attention is paid to investigation of the role of specific conditions at the inner and outer boundaries of the simulation domain, under which different regimes of material escape (free- and restricted- flow) are formed. Comparative study of different processes, such as XUV heating, material ionization and recombination, H3+ cooling, adiabatic and Lyman-alpha cooling, Lyman-alpha reabsorption is performed. We confirm basic consistence of the outcomes of our modeling with the results of other hydrodynamic models of expanding planetary atmospheres. In particular, we obtain that under the typical conditions of an orbital distance 0.05 AU around a Sun-type star a Hot Jupiter plasma envelope may reach maximum temperatures up to ~9000K with a hydrodynamic escape speed ~9 km/s resulting in the mass loss rates ~(4-7)*10^10 g*s . In the range of considered stellar-planetary parameters and XUV fluxes that is close to mass loss in the energy limited case. The inclusion of planetary intrinsic magnetic fields in the model is a subject of the following up paper (Paper II).

astro-ph.EP↗

arXiv2011

Small scale magnetosphere: Laboratory experiment, physical model and Hall MHD simulation

A problem of magnetosphere formation on ion inertia scale around weakly magnetized bodies is investigated by means of laboratory experiment, analytical analysis and 2.5D Hall MHD simulation. Experimental evidence of specific magnetic field generated by the Hall term is presented. Direct comparison of regimes with small and large ion inertia length revealed striking differences in measured magnetopause position and plasma stand off distance. Analytical model is presented, which explains such basic features of mini-magnetosphere observed in previous kinetic simulations as disappearance of bow shock and plasma stopping at Stoermer particle limit instead of pressure balance distance. Numerical simulation is found to be in a good agreement with experiments and analytical model. It gives detailed spatial structure of Hall field and reveals that while ions penetrate deep inside mini-magnetosphere electrons overflow around it along magnetopause boundary.

physics.space-ph↗