Model Of Solar Wind Interaction Research Articles

Adiabatic energy change in the inner heliosheath: how does it affect the distribution of pickup protons and energetic neutral atom fluxes?

ABSTRACT The hydrogen atoms penetrate the heliosphere from the local interstellar medium, and while being ionized, they form the population of pickup protons. The distribution of pickup protons is modified by the adiabatic heating (cooling) induced by the solar wind plasma compression (expansion). In this study, we emphasize the importance of the adiabatic energy change in the inner heliosheath that is usually either neglected or considered improperly. The effect of this process on the energy and spatial distributions of pickup protons and energetic neutral atoms (ENAs), which originate in the charge exchange of pickup protons, has been investigated and quantified using a kinetic model. The model employs the global distributions of plasma and hydrogen atoms in the heliosphere from the simulations of a kinetic-magnetohydrodynamic model of solar wind interaction with the local interstellar medium. The findings indicate that the adiabatic energy change is responsible for the broadening of the pickup proton velocity distribution and the significant enhancement of ENA fluxes (up to ∼5 and ∼20 times in the upwind and downwind directions at energies ∼1–2 keV for an observer at 1 au). It sheds light on the role of adiabatic energy change in explaining the discrepancies between the ENA flux observations and the results of numerical simulations.

Ionization of Interstellar Hydrogen Beyond the Termination Shock

Models of solar wind interaction with the surrounding interstellar medium usually disregard ionization of interstellar hydrogen atoms beyond the solar wind termination shock. If and when included, the effects of ionization in the heliospheric interface region are often obscured by complexities of the interaction. This work assesses the importance of interstellar hydrogen ionization in the heliosheath. Photoionization could be accounted for in a straightforward way. In contrast, electron impact ionization is largely unknown because of poorly understood energy transfer to electrons at the termination shock and beyond. We first estimate the effect of photoionization and then use it as a yardstick to assess the role of electron impact ionization. The physical estimates show that ionization of interstellar hydrogen may lead to significant mass loading in the inner heliosheath which would slow down plasma flowing toward the heliotail and deplete populations of nonthermal protons, with the corresponding effect on heliospheric fluxes of energetic neutral atoms.

A Magnetohydrodynamic Model of Solar Wind Interaction with Asteroid Gaspra

The solar wind response to a small-sized magnetized body is modeled on the basis of a two-dimensional magnetohydrodynamic (MHD) plasma description including Hall current corrections (Hall-MHD model). Basic features of the magnetic signatures observed near Galileo's closest approach to asteroid Gaspra are reproduced, assuming Gaspra's magnetic dipole momentto be of the order of 10(14) ampere.meters squared and tilted to the solar wind flow direction at an angle of about 45 degrees .

Gasdynamics of the solar wind interaction with the interstellar medium

A survey of the present-day situation in gasdynamical models of solar wind interaction with the local interstellar medium is presented. A role of these models in interpreting a number of observed physical phenomena is investigated. Experimental data and possible observations are considered from the viewpoint of their interpretation on the basis of theoretical models. Our attention is concentrated on the main limitations of the gasdynamical models, in particular, two-shocks model developed by Baranovet al. (1981, 1982).

Steady state flow/field model of solar wind interaction with Venus: Global implications of local effects

The structure and variability of ion concentrations, velocities, and electric and magnetic fields in the ionosphere of Venus result from a combination of physical and chemical processes driven by the interaction of the solar wind with the atmosphere of Venus. In this paper we describe these processes and formulate a model describing their interrelationships in a self‐consistent manner. We show that the consequences of this model are in agreement with Pioneer Venus observations in the Venus ionosphere. It is shown that the magnetic field configuration of the Venus ionosphere is a steady state global structure which results from a combination of a large‐scale “open” current system connecting through the ionopause to the postshock solar wind and two small‐scale “closed” current systems entirely confined within the ionosphere itself and generated by ionospheric flows and shears. A previously detected ionospheric layer in O2+ near 170 km altitude is shown to be a new type of ionospheric layer resulting from transition of solar‐wind‐driven vertical flow to velocities approaching Mach 1 (sonic flow). Accordingly, this layer has been named the “sonic flow layer” or “S layer.” It is suggested that this model should apply to other nonmagnetic bodies in magnetized plasma flows, such as comets and Jovian satellites.

Solar wind interaction with comet Halley

In March 6 and 9, 1986 the spacecrafts ‘Vega-1’ and ‘Vega-2’ have flown through the coma of comet Halley and have carried measurements of plasma, energetic particles, magnetic field and plasma waves along its trajectory. A short review of these measurements and its comparison with theoretical models of solar wind interaction with comets are given. The spacecrafts ‘Vega-1’ and ‘Vega-2’ have studied the solar wind loading by cometary ions, the structure of cometary bow shock and the processes in the inner coma of comet Halley. Exactly in this sequence we discuss the results of measurements and compare them with the theory.

Magnetic field structure behind the Moon

Details concerning the magnetic field structure expected on the basis of the author's model of solar wind interaction with the moon are discussed. A derivation is presented that supports the finding of Colburn et al. that the magnetic field in the plasma void region downstream of the moon (relative to the solar wind flow) is more intense than the ambient interplanetary magnetic field. In the expansion region surrounding the void, the field is less than ambient. These effects should be smallest when the magnetic field is perpendicular to the flow vector. A standing shock wave trailing several lunar radii behind the moon is expected regardless of the magnetic field orientation.