Publication Date:
2016-06-25
Description:
The trailing-edge rarefactions of 54 high-speed streams at 1 AU are analyzed. The temporal durations of the trailing-edge rarefactions agree with ballistic calculations based on the observed speeds of the fast and slow wind bounding the rarefactions. A methodology is developed to measure solar-wind compression and rarefaction using the orientations of solar-wind current sheets. One focus is to determine the signature that best describes the location of the trailing-edge stream interface between coronal-hole-origin plasma and streamer-belt-origin plasma; based on the current-sheet orientations, on the magnetic-field strength, on the intensity of the electron strahl, and on the intensity of the negative vorticity, an inflection point in the temporal profile of the solar-wind velocity is taken as the best indicator of the trailing-edge stream interface. Computer simulations support this choice. Using superposed-epoch analysis, the plasma properties and turbulence properties of trailing-edge rarefactions are surveyed. Whereas the signatures of the coronal-hole/streamer-belt (slow-wind/fast-wind) boundary in the leading edge (CIR) stream interface are simultaneous, they are not simultaneous in the trailing edge, with ion-charge-state signatures occurring on average 13.7 hours prior to the proton-entropy signature. It is suggested that differences in the leading and trailing edges of coronal holes on the Sun might account for the differences in the leading and trailing edges of high-speed streams at 1 AU: the formation timescales, heating timescales, and charge-state-equilibration timescales of closed flux loops in the corona might be involved.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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