Evolution of solar wind structures from 0.72 to 1 AU |
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| Authors: | L Jian CT Russell JG Luhmann RM Skoug |
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| Institution: | 1. Institute of Geophysics and Planetary Physics, University of California, Los Angeles, 595 Charles E. Young Drive East, 6862 Slichter, Los Angeles, CA 90095, USA;2. Institute of Geophysics and Planetary Physics, University of California, Los Angeles, 595 Charles E. Young Drive East, 6869 Slichter, Los Angeles, CA 90095, USA;3. Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA;4. Space Science and Applications, Los Alamos National Laboratory, Los Alamos, NM 87545, USA |
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| Abstract: | Understanding the evolution of solar wind structures in the inner heliosphere as they approach the Earth is important to space weather prediction. From the in situ solar wind plasma and magnetic field measurements of Pioneer Venus Orbiter (PVO) at 0.72 AU (1979–1988), and of Wind/Advanced Composition Explorer (ACE) missions at 1 AU (1995–2004), we identify and characterize two major solar wind structures, stream interaction regions (SIRs) and interplanetary coronal mass ejections (ICMEs). The average percentage of SIRs occurring with shocks increases significantly from 3% to 24% as they evolve from 0.72 to 1 AU. The average occurrence rate, radial extent, and bulk velocity variation of SIRs do not change from 0.72 to 1 AU, while peak pressure and magnetic field strength both decrease with the radial evolution of SIRs. Within the 0.28 AU distance from the orbit of Venus to that of Earth, the average fraction of ICMEs with shocks increases from 49% to 66%, and the typical radial extent of ICMEs expands by about a fraction of 1.4, with peak pressure and magnetic field strength decreasing significantly. The mean occurrence rate and expansion velocity of ICMEs do not change from 0.72 to 1 AU. |
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| Keywords: | Interplanetary coronal mass ejection or ICME Stream interaction Radial evolution Pioneer Venus Orbiter or PVO |
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