Dynamics of large-scale solar-wind streams obtained by the double superposed epoch analysis. 3. Deflection of speed vector

TL;DR

This study analyzes the deflection of solar wind streams' velocity vectors using double superposed epoch analysis, revealing opposite deflection directions in different interplanetary structures and examining angular variations.

Contribution

First analysis of average temporal profiles of velocity vector angles in large-scale solar wind streams, highlighting deflection behaviors in CIRs, Sheaths, and ICMEs.

Findings

Velocity vector deflects opposite in CIR/Sheath and ICME.

Angles in the ecliptic plane tend to increase due to solar rotation.

Average latitude angle remains nearly constant around 1 degree.

Abstract

This work is a continuation of our previous articles (Yermolaev et al. in J. Geophys.Res. 120, 7094, 2015, Yermolaev et al. in Solar Phys. 292, 193, 2017), which describe the average temporal profiles of interplanetary plasma and field parameters in large-scale solar-wind (SW) streams: corotating interaction regions (CIRs), interplanetary coronal mass ejections (ICMEs including both magnetic clouds (MCs) and ejecta), and sheaths as well as interplanetary shocks (ISs). Changes of longitude angle {\phi} in CIRs from -2 to +2{\deg} agree with earlier observations. Besides we have for the first time analyzed the average temporal profiles of bulk velocity angles in Sheaths and ICMEs and found that the angle {\phi} in ICME changes from 2 to -2{\deg} while in Sheath it changes from -2 to 2{\deg} (similar to change in CIR), i.e., the streams in CIR/Sheath and ICME deflects in the opposite side. When averaging the latitude angle {\theta} on all intervals of the chosen SW type, the angle {\theta} is almost constant ~1{\deg}. We made selection of SW events with increasing and decreasing angle {\theta} for the first time and found that average temporal profiles for angle {\theta} in selected events have the same <<integral-like>> shape as for angle {\phi}. The difference in average profiles for angles {\phi} and {\theta} is explained by the fact that most events have increasing profiles for angle in ecliptic plane due to solar rotation while for angle in meridional plane numbers of increasing and decreasing profiles are equal.