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; 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 sheath as well as interplanetary shocks (ISs). Changes of longitude angle φ in CIRs from -2 to +2° 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 φ in ICME changes from 2 to −2° while in Sheath it changes from −2 to 2° (similar to change in CIR), i.e., the streams in CIR/Sheath and ICME deflect in the opposite side. When averaging the latitude angle ϑ on all intervals of the chosen SW type, the angle ϑ is almost constant ~1°. We made selection of SW events with increasing and decreasing angle ϑ for the first time and found that average temporal profiles for angle ϑ in selected events have the same "integral-like" shape as for angle φ. The difference in average profiles for angles φ and ϑ 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.

Cosmic noise absorption signature of particle precipitation during interplanetary coronal mass ejection sheaths and ejecta

“…We have also resampled the data (increased or decreased the time between the time intervals) during the sheath and ejecta structures to the same average durations of 9.5 and 21.5 h, respectively (for a similar approach see e.g. Kilpua et al, 2015;Masías-Meza et al, 2016;and Yermolaev et al, 2018). This approach is useful for investigating overall patterns in solar-wind and geomagnetic conditions and precipitation signatures for structures that exhibit a large range of durations (e.g.…”

“…Bortnik et al, 2008;Hartley et al, 2018). The EMIC waves in turn occur predominantly in the duskside of the magnetosphere close to the plasmapause, as they are generated by anisotropic ring current proton distributions (Zhang et al, 2016;Saikin et al, 2016).…”

Dynamics of Large‐Scale Solar‐Wind Streams Obtained by the Double Superposed Epoch Analysis: 4. Helium Abundance

“…In the present paper, we use the same database and methods as in our previous works (Yermolaev et al, 2015(Yermolaev et al, , 2017(Yermolaev et al, , 2018: (1) the 1-hr interplanetary plasma and magnetic field data of the OMNI2…”

“…As has been indicated in the Introduction, in this work, we use an extended set of SW events. In contrast with our previous works (Yermolaev et al, 2015(Yermolaev et al, , 2017(Yermolaev et al, , 2018, where we analyzed the 25-year data set for 1976-2000, here we study the 41-year data set with ACE N α /N p data for the period of 1976-2016 and the 42-year set without ACE N α /N p data for the period of 1976-2017 (see Figure 1 for a comparison of the availability of OMNI2 data for these periods). As a result, the number of events in the new 41-and 42-year data sets turned out to be more than double the number in the old 25-year data set.…”

“…Yearly numbers of the 1-hr data from the OMNI2 data set for the period of 1976-2017: plasma (density N, velocity V, and temperature T) and magnetic field (IMF magnitude and components) data (black points), relative helium abundance N α /N p with ACE data (red points), and relative helium abundance N α /N p without ACE data (green rhomboids). The data to the left of the dashed line were used in previous publications (Yermolaev et al, 2015(Yermolaev et al, , 2017(Yermolaev et al, , 2018.…”