http://arxiv.org/abs/2304.00274
Although the enhancements in the alpha-proton ratio in the solar wind (expressed as $A_{He} = N_{a}/N_p*100$) in the Interplanetary Coronal Mass Ejections (ICMEs) have been studied in the past, $A_{He}$ enhancements at the stream interface region received very little attention so far. In this letter, by extensively analyzing the stream interaction region (SIR) events observed in solar cycle 23 and 24, we show that the stream interface of alphas starts separating out from that of protons from the minimum of solar cycle 23. We show that more alpha particles are distributed towards higher pitch angles as compared to protons in the fast wind region compared to background solar wind. By analysing the differential velocities of alphas and protons, we also show that the faster alpha particles accumulate near the fast wind side of the stream interface region leading to enhancement of $A_{He}$. The investigation brings out, for the first time, the salient changes in $A_{He}$ in SIRs for the two solar cycles and highlight the important roles of pitch angle and differential velocities of alpha and protons in the fast wind region for the changes in $A_{He}$ in SIRs.
Y. Yogesh, D. Chakrabarty and N. Srivastava
Tue, 4 Apr 23
45/111
Comments: N/A