Ion escape from the upper ionosphere of Titan triggered by the solar wind

Abstract

The observed escape of ions from the ionosphere of Titan suggests a potential role of the solar wind in the interaction with the upper atmospheric layers. We investigate such a plausible scenario using a hydrodynamic fluid approach for the plasma expansion in the upper ionosphere of Titan, combining (Maxwellian) electrons and three different species of positive ions which interact with the solar wind electrons and protons. Using a self-similar transformation, numerical analysis is performed to solve the basic equations, and characterize the plasma density, velocity, and electric potential during the expansion. It is found that increasing the solar wind proton number density leads to a reduction the ion escape, while the effect of electrons is opposite stimulating the ion escape. Moreover, the expansion domain does not change for more energetic protons. The heavier ions has the leading role in controlling the ion escape, i.e. by comparison to CH + 5 ions, C 2 H + 5 ions appear to have a more influence in the loss from Titan ionosphere. For a higher temperature contrast between ions and electrons, the depletion rate of the density increases and the ions move faster, leading to a higher ionic loss.

Role of solar wind on the ionic escaping from Venus upper ionosphere via plasma wakefield

“…Moslem et al [22] and Salem et al [23] used a plasma expansion approach as a plausible mechanism to explain the escaping of charged particles from the upper ionosphere of Titan and Venus. Moslem et al [16] proposed another mechanism to describe the ionic loss at Venus.…”

“…In the present study we used the test charge approach which studies the 'small amplitude scale' of ionic escaping in the plasma system. However, in [22,23] they used a plasma expansion or self-similar approach which used a fluid-like model to characterize the 'large amplitude scale' i.e. fully nonlinear dynamics of the ionized particles.…”

Propagation of different kinds of non-linear ion-acoustic waves in Earth’s magnetosphere

“…To understand the behaviour and properties of different types of wave solutions to non-linear differential equations, investigative analysis must occur due to the increased interest in the field of space research in recent years. There are many theoretical studies on the properties of plasma fluid formed in the Earth's ionosphere or on other planets including Ali et al (2021); Tolba et al (2017Tolba et al ( , 2021; Salem et al (2017), and Moslem et al (2019a). Many different non-linear effects occur on ionospheric plasma under the influence of strong radio emissions according to Levine et al (2020); Golikov et al (2016); Pavlov et al (2000), and Ma et al (2012).…”

The Role of Superthermal Electrons on the Escaping Ions From the Upper Atmosphere of Titan and Venus

“…Unlike our planet Earth, Venus and Titan moon lack to a global internally generated magnetic field [1], which make them heavily exposed to the solar wind strikes [2] and [3]. Although Titan is located inside Saturn's magnetic umbrella for most of its orbiting time, it is magnetically unprotected orbiting Saturn for about 7 hours out of Saturn's magnetosphere [4].…”

“…The effects of different plasma parameters, i.e., density and temperature ratios, were studied on the expanding plasma profiles. Later, Moslem et al [2] investigated the ionic escape from the upper ionosphere of Titan triggered by the solar wind. In this work, a plausible scenario using a hydrodynamic fluid approach for the plasma expansion in the upper ionosphere of Titan, combining (Maxwellian) electrons and three different species of positive ions which interact with the solar wind electrons and protons.…”