Stability of the interstellar hydrogen inflow longitude from 20 years of SOHO/SWAN observations

Abstract

Aims. A recent debate on the decade-long stability of the interstellar He flow vector, and in particular the flow longitude, has prompted us to check for any variability in the interstellar H flow vector as observed by the SWAN instrument on board SOHO. Methods. We used a simple model-independent method to determine the interstellar H flow longitude, based on the parallax effects induced on the Lyman-α intensity measured by SWAN following the satellite motion around the Sun. Results. Our results show that the interstellar H flow vector longitude does not vary significantly from an average value of 252.9${}^{\circ }$ $\pm$ 1.4${}^{\circ }$ throughout the 20-year span of the SWAN dataset, further strengthening the arguments for the stability of the interstellar gas flow.

arXiv comment6 pages, 7 figures, Astronomy & Astrophysics in press

References in corpus (7)

• Interstellar neutral helium in the heliosphere from IBEX observations. III. Mach number of the flow, velocity vector, and temperature from the first six years of measurements
• Filtration of interstellar hydrogen in the two-shock heliospheric interface: Inferences on the local interstellar electron density
• The Interstellar H Flow: Updated Analysis of SOHO/SWAN Data
• On the Decades-Long Stability of the Interstellar Wind through the Solar System
• Interstellar Neutral Helium in the Heliosphere from IBEX Observations. I. Uncertainties and Backgrounds in the Data and Parameter Determination Method
• Neutral interstellar helium parameters based on Ulysses/GAS and IBEX-Lo observations: what are the reasons for the differences?
• Interplanetary Lyman $\alpha$ line profiles: variations with solar activity cycle

Cited by in corpus (5)

• The interface between the outer heliosphere and the inner lism: Morphology of the local interstellar cloud, its hydrogen hole, stromgren shells, and ${}^{60}$Fe accretion
• Quiet-Sun hydrogen Lyman-alpha line profile derived from SOHO/SUMER solar-disk observations
• Backscattered solar Lyman-alpha emission as a tool for the heliospheric boundary exploration
• On the feasibility of studying the exospheres of Earth-like exoplanets by Lyman-alpha monitoring. Detectability constraints for nearby M stars
• The flow direction of interstellar neutral H from SOHO/SWAN