Ion-driven instabilities in the solar wind: Wind observations of 19 March 2005

Journal Article · Sat Jan 16 04:00:00 UTC 2016 · Journal of Geophysical Research. Space Physics

DOI: https://doi.org/10.1002/2015JA021935 · OSTI ID:1255080

Gary, S. Peter ^[1]; Jian, Lan K. ^[2]; Broiles, Thomas W. ^[3]; Stevens, Michael L. ^[4]; Podesta, John J. ^[1]; Kasper, Justin C. ^[5]

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1. Space Science Institute, Boulder CO (United States)
2. Univ. of Maryland, College Park, MD (United States). Goddard Planetary Heliophysics Institute; NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
3. Southwest Research Institute, San Antonio, TX (United States)
4. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
5. Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Atmospheric, Oceanic, and Space Sciences

Intervals of enhanced magnetic fluctuations have been frequently observed in the solar wind. However, it remains an open question as to whether these waves are generated at the Sun and then transported outward by the solar wind or generated locally in the interplanetary medium. Magnetic field and plasma measurements from the Wind spacecraft under slow solar wind conditions on 19 March 2005 demonstrate seven events of enhanced magnetic fluctuations at spacecraft-frame frequencies somewhat above the proton cyclotron frequency and propagation approximately parallel or antiparallel to the background magnetic field B_o. The proton velocity distributions during these events are characterized by two components: a more dense, slower core and a less dense, faster beam. In conclusion, observed plasma parameters are used in a kinetic linear dispersion equation analysis for electromagnetic fluctuations at k x B_o = 0; for two events the most unstable mode is the Alfvén-cyclotron instability driven by a proton component temperature anisotropy T_⊥/T_|| > 1 (where the subscripts denote directions relative to B_o), and for three events the most unstable mode is the right-hand polarized magnetosonic instability driven primarily by ion component relative flows. Thus, both types of ion anisotropies and both types of instabilities are likely to be local sources of these enhanced fluctuation events in the solar wind.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC52-06NA25396
• OSTI ID: 1255080
• Report Number(s): LA-UR--15-27210
• Journal Information: Journal of Geophysical Research. Space Physics, Journal Name: Journal of Geophysical Research. Space Physics Journal Issue: 1 Vol. 121; ISSN 2169-9380
• Publisher: American Geophysical UnionCopyright Statement
• Country of Publication: United States
• Language: English