Chandrayaan‐1 observations of backscattered solar wind protons from the lunar regolith: Dependence on the solar wind speed. Issue 5 (7th May 2014)

• Record Type: Journal Article
• Authors: Lue, Charles; Futaana, Yoshifumi; Barabash, Stas; Wieser, Martin; Bhardwaj, Anil; Wurz, Peter
• Is Part Of: Journal of geophysical research. Volume 119:Issue 5(2014:May)
• Page Start: 968
• Page End: 975
• Publication Date: 2014-05-07
• Subjects: Planets -- Periodicals; Geophysics -- Periodicals; 559.9
• DOI: 10.1002/2013JE004582
• Languages: English
• ISSNs: 2169-9097

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>We study the backscattering of solar wind protons from the lunar regolith using the Solar Wind Monitor of the Sub‐keV Atom Reflecting Analyzer on Chandrayaan‐1. Our study focuses on the component of the backscattered particles that leaves the regolith with a positive charge. We find that the fraction of the incident solar wind protons that backscatter as protons, i.e., the proton‐backscattering efficiency, has an exponential dependence on the solar wind speed that varies from ~0.01% to ~1% for solar wind speeds of 250 km/s to 550 km/s. We also study the speed distribution of the backscattered protons in the fast (~550 km/s) solar wind case and find both a peak speed at ~80% of the solar wind speed and a spread of ~85 km/s. The observed flux variations and speed distribution of the backscattered protons can be explained by a speed‐dependent charge state of the backscattered particles.</p> </abstract>