Abstract
Observations of plasma and turbulence in the outer heliosphere (the distant supersonic solar wind and the subsonic solar wind beyond the heliospheric termination shock) made by the Voyager Interstellar Mission and the energetic neutral atom observations made by the IBEX spacecraft have revealed that the underlying plasma in the outer heliosphere and very local interstellar medium (VLISM) comprises distinct thermal proton and electron and suprathermal pickup ion (PUI) populations. Estimates of the appropriate collisional frequencies show that the multi-component plasma is not collisionally equilibrated in either the outer heliosphere or VLISM. Furthermore, suprathermal PUIs in these regions form a thermodynamically dominant component. We review briefly a subset of the observations that led to the realization that the solar wind–VLISM interaction region is described by a non-equilibrated multi-component plasma and summarizes the derivation of suitable plasma models that describe a PUI-mediated plasma.
Highlights
The Voyager 1 (V1) spacecraft crossed the heliopause, the boundary separating matter of solar origin from interstellar matter, and entered the local interstellar medium (LISM) during August 2012 (Stone et al 2013; Krimigis et al 2013; Burlaga et al 2013; Gurnett et al 2013), an event of enormous historical import for humankind
We have the opportunity to study in situ basic plasma physical processes in the interstellar medium (ISM)
We review briefly our understanding of the basic plasma physics model that is beginning to emerge as a result of observations made by the Voyager interstellar mission (Voyagers 1 and 2) and the
Summary
The Voyager 1 (V1) spacecraft crossed the heliopause, the boundary separating matter of solar origin from interstellar matter, and entered the local interstellar medium (LISM) during August 2012 (Stone et al 2013; Krimigis et al 2013; Burlaga et al 2013; Gurnett et al 2013), an event of enormous historical import for humankind. The isotropized PUIs form a distinct suprathermal population of energetic ions (∼1 keV energies in the supersonic SW, with a number density approximately 20 % of the solar wind number density in the vicinity of the HTS) in the plasma whose origin is either the interstellar medium when considering region 3 and 2. To address the lower energies, Zirnstein et al (2014) extended the Zank et al (2010) model in two ways They accounted for the extinction of solar wind protons and transmitted and reflected PUIs by charge exchange with interstellar neutral H in the composite proton distribution. The results from the theoretical models (Zank et al 2010; Zirnstein et al 2014) describing the interaction of the solar wind and the partially ionized LISM and the observational results (Desai et al 2012, 2014) confirm that the IHS and VLISM are multi-component non-equilibrated plasmas.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
