Dynamics of Large-Scale Solar-Wind Streams Obtained by the Double Superposed Epoch Analysis: 3. Deflection of the Velocity Vector

Abstract

This work is a continuation of our previous articles (Yermolaev et al. in J. Geophys. Res. 120, 7094, 2015 and 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 in the longitude angle, $\varphi$, in CIRs from −2 to $2^{\circ}$ agree with earlier results (e.g. Gosling and Pizzo, 1999). We have also analyzed the average temporal profiles of the bulk velocity angles in sheaths and ICMEs. We have found that the angle $\varphi$ in ICMEs changes from 2 to $-2^{\circ}$, while in sheaths it changes from −2 to $2^{\circ}$ (similar to the change in CIRs), i.e. the angle in CIRs and sheaths deflects in the opposite sense to ICMEs. When averaging the latitude angle $\vartheta$ on all the intervals of the chosen SW types, the angle $\vartheta$ is almost constant at ${\sim}\,1^{\circ}$. We made for the first time a selection of SW events with increasing and decreasing $\vartheta$ and found that the average $\vartheta$ temporal profiles in the selected events have the same “integral-like” shape as for $\varphi$. The difference in $\varphi$ and $\vartheta$ average profiles is explained by the fact that most events have increasing profiles for the angle in the ecliptic plane as a result of solar rotation, while for the angle in the meridional plane, the numbers of events with increasing and decreasing profiles are equal.