Energetic particles, tangential discontinuities, and solar flux tubes

• Published in: Journal of geophysical research. Space physics 2015-10, Vol.120 (10), p.8281-8287
• Main Authors: Neugebauer, M., Giacalone, J.
• Format: Article
• Language: English
• Subjects: Acceleration; Atoms & subatomic particles; Boundaries; Charged particles; discontinuities; Discontinuity; Energetic particles; Fluctuations; Flux; flux tube boundaries; Low energy; Magnetic fields; Solar wind; Tubes
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1002/2015JA021632

This study examines the probable sources of sharp changes in the flux of energetic particles (EPs) in the solar wind. Data acquired by the ACE Low Energy Magnetic Spectrometer sensors during 1999 were used to identify EP boundaries that were not located at interplanetary shocks or caused by intermittent connection to the Earth's bow shock. It was found that at least 68%, and probably 80%, of such boundaries occur at significant changes in the plasma and magnetic field in the solar wind. Those changes are consistent with crossing preexisting tangential discontinuities or flux tube boundaries rather than by local MHD turbulence or time‐dependent bursts of acceleration. Because some of the EP boundaries would not have been detected by Borovsky's (2008) analysis of flux tube boundaries, it is concluded that such boundaries in the solar wind are at least 30% more prevalent than previously suggested. The result can also be used to explain some observations of localized variations in EP flux both ahead of and behind the interplanetary shocks where particle acceleration occurred without requiring local acceleration. Key Points Changes in low‐energy particle flux are associated with flux tube boundaries Some flux tube boundaries are not associated with major magnetic structures Particle flux boundaries are consistent with changes in solar wind plasma