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Helium abundance and non-equilibrium in the inner heliosphere

Authors :
Niembro Hernandez, T.
Stevens, M. L.
Case, A. W.
Korreck, K. E.
Paulson, K.
Szypko, G. M.
Kasper, J. C.
Larson, D. E.
Livi, R.
Rahmati, A.
Mcmanus, M.
Huang, J.
Szabo, A.
Whittlesey, P. L.
Bale, S.
Pulupa, M.
Malaspina, D.
Bonnell, J. W.
Harvey, P.
Goetz, K.
Dudok de Wit, Thierry
Macdowall, R. J.
POTHIER, Nathalie
Publication Year :
2019
Publisher :
HAL CCSD, 2019.

Abstract

The solar wind is known to be a hot, mostly-collisionless plasma that expands beyond the solar system domain. At closer distances to the Sun, the plasma is found to be less spatially uniform and further from local thermodynamic equilibrium. It is there that the Parker Solar Probe SWEAP experiment analyzes the kinetic properties of the plasma between different ion species in order to study different kinetic and thermodynamic processes involved in the solar wind evolution. The Solar Probe Cup (SPC) continuously measures fast, high-resolution measurements of the radial charge-flux distribution of solar wind ions. In these measurements, however, the hydrogen and helium components frequently overlap, making it very difficult to determine the density, velocity and temperature of the helium component. The Solar Probe ion Analyzer (SPAN-i), meanwhile, measures hydrogen and helium particle flux distributions in a variety of modes, including three-dimensional and mass-discriminating modes that are executed at varied cadences and resolutions. In this work, we combine simultaneous measurements of solar wind helium from the Faraday Cup and electrostatic analyzers in order to disentangle the two species in the SPC measurements. In so doing, we derive a rapid helium abundance ratio, relative speed, and temperature in the inner heliosphere. Using the helium abundance as a tracer of solar wind streams, we then compare the kinetic states of similar streams observed along the Parker Solar Probe encounter to their evolved states out at 1 AU with measurements from Wind spacecraft.

Details

Language :
English
Database :
OpenAIRE
Accession number :
edsair.od.......166..c602041839d9a7b505814bfb25fc010e