Outside Earth’s Bow Shock with HPCA: Ions From Multiple Sources
Presentation Type
Talk
Presenter Format
In Person Meeting Talk
Topic
System Science
Start Date
12-5-2022 1:45 PM
Abstract
The Hot Plasma Composition Analyzers (HPCA) onboard the MMS spacecraft provide a unique opportunity to study various ion species from different sources when operated in the interplanetary environment. Plasma outside the Earth’s bow shock is composed of the solar wind, interstellar neutrals, and the Earth’s extended exosphere. When the dominant signal of the solar wind protons is filtered out, hydrogen, helium, and oxygen ions are revealed. This study focuses on them and their origin.
Interstellar neutrals (ISNs) originate in the local interstellar medium and constantly stream into the heliosphere where they are affected by solar gravity and the solar radiation environment. The solar gravity enhances ISN densities close to the Sun along the gas inflow direction. At the same time, the solar radiation environment counteracts gravity by reducing atomic fluxes via ionization processes and radiation pressure in the case of interstellar hydrogen. Pickup ions (PUIs) are created when the ISNs are ionized by solar radiation. They serve as a diagnostic tool for the ISN gas characteristics, e.g., velocity vector. We discuss the expected distribution of the parent ISNs and their PUIs along Earth’s orbit for various phases of solar activity. We also elaborate on opportunities that MMS gives to advance the understanding of PUI spatial and temporal variations in the Earth’s vicinity.
Outside Earth’s Bow Shock with HPCA: Ions From Multiple Sources
The Hot Plasma Composition Analyzers (HPCA) onboard the MMS spacecraft provide a unique opportunity to study various ion species from different sources when operated in the interplanetary environment. Plasma outside the Earth’s bow shock is composed of the solar wind, interstellar neutrals, and the Earth’s extended exosphere. When the dominant signal of the solar wind protons is filtered out, hydrogen, helium, and oxygen ions are revealed. This study focuses on them and their origin.
Interstellar neutrals (ISNs) originate in the local interstellar medium and constantly stream into the heliosphere where they are affected by solar gravity and the solar radiation environment. The solar gravity enhances ISN densities close to the Sun along the gas inflow direction. At the same time, the solar radiation environment counteracts gravity by reducing atomic fluxes via ionization processes and radiation pressure in the case of interstellar hydrogen. Pickup ions (PUIs) are created when the ISNs are ionized by solar radiation. They serve as a diagnostic tool for the ISN gas characteristics, e.g., velocity vector. We discuss the expected distribution of the parent ISNs and their PUIs along Earth’s orbit for various phases of solar activity. We also elaborate on opportunities that MMS gives to advance the understanding of PUI spatial and temporal variations in the Earth’s vicinity.
