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(Non)radial Solar Wind Propagation through the Heliosphere

2020; IOP Publishing; Volume: 897; Issue: 2 Linguagem: Inglês

10.3847/2041-8213/ab9ff7

2041-8213

Zdeněk Němeček, Tereza Ďurovcová, Jana Šafránková, J. D. Richardson, Jiřı́ Šimůnek, M. L. Stevens,

Astro and Planetary Science

Abstract The solar wind nonradial velocity components observed beyond the Alfvén point are usually attributed to waves, the interaction of different streams, or other transient phenomena. However, Earth-orbiting spacecraft as well as monitors at L1 indicate systematic deviations of the wind velocity from the radial direction. Since these deviations are of the order of several degrees, the calibration of the instruments is often questioned. This paper investigates for the first time the evolution of nonradial components of the solar wind flow along the path from ≈0.17 to 10 au. A comparison of observations at 1 au with those closer to or farther from the Sun based on measurements of many spacecraft at different locations in the heliosphere (Parker Solar Probe, Helios 1 and 2, Wind, Advanced Composition Explorer, Spektr- R , Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) probes, Mars Atmosphere and Volatile Evolution (MAVEN), Voyagers 1 and 2) shows that (i) the average values of nonradial components are not zero and vary in a systematic manner with the distance from the Sun and (ii) their values significantly depend on the solar wind radial velocity.