Statistical dependence of ion-scale waves’ spacecraft-frame polarization observed by Parker Solar Probe on local proton and alpha non-Maxwellian features

ABSTRACT This paper statistically investigate the relationship between the polarization of ion-scale waves in the spacecraft frame and the background plasma environment based on parker solar probe observations within 0.3 au. Our statistical results show that the background solar wind environment of left-handed (LH) and right-handed (RH) ion-scale waves in the spacecraft frame is significantly different. The LH waves corresponds to higher ion temperature ($T_\mathrm{ p}\sim 45.16$ eV, $T_{\alpha }\sim 327.63$ eV), larger alpha particle density ratio ($N_{\alpha }/N_\mathrm{ p}\sim 0.016$), larger temperature ratio ($T_{\alpha }/T_\mathrm{ p}\sim 7.20$), and larger differential speed ($(V_{\alpha }-V_\mathrm{ p})/V_\mathrm{ A}\sim 0.395$) than those ($T_\mathrm{ p}\sim 18.38$ eV, $T_{\alpha }\sim 77.25$ eV, $N_{\alpha }/N_\mathrm{ p}\sim 0.007$, $T_{\alpha }/T_\mathrm{ p}\sim 4.22$, $(V_{\alpha }-V_\mathrm{ p})/V_\mathrm{ A}\sim 0.093$) of RH waves. In addition, LH waves mainly corresponds to $V_{\alpha \mathrm{ p}}/V_\mathrm{ A}\gt 0$ (the moment of alpha velocity is larger than the moment of proton velocity) and their occurrence rate of LH ion-scale waves is proportional to $T_{\alpha }$, $T_\mathrm{ p}$, $T_{\alpha }/T_\mathrm{ p}$, $T_{\alpha \parallel }/T_{\mathrm{ p} \parallel }$, and $V_{\alpha \mathrm{ p}}/V_\mathrm{ A}$, while RH waves do the opposite. Moreover, when $T_{\alpha }/T_\mathrm{ p}\gt 10$, only LH ion-scale wave exists and its occurrence rate is high. Besides, our theoretical results suggest that the high occurrence rate regions of spacecraft-frame LH (RH) ion-scale waves seem to prefer generating LH Alfvén/ion cyclotron waves (RH fast magnetosonic/whistler waves).