Alpha/proton Instability in the Presence of Proton and Alpha Temperature Anisotropy and its Application to the Deceleration of Alpha Particles in the Solar Wind  

作　　者：Wen-Lu Zhang Liang Xiang Qiu-Huan Li Si-Yi Lang Hong-Wei Yu 

机构地区：[1]Department of Physics and Synergetic Innovation Center for Quantum Effects and Applications,School of Physics and Electronics,Hunan Normal University,Changsha 410081,China [2]Institute of Space Physics,Luoyang Normal University,Luoyang 471934,China

出　　处：《Research in Astronomy and Astrophysics》2022年第1期192-204,共13页天文和天体物理学研究（英文版）

基　　金：supported by the National Natural Science Foundation of China under grants 12103018,11690034,and 12075084;supported by the Science and Technology Innovation Program of Hunan Province(2020RC2049)。

摘　　要：Observations of solar wind plasma find that the drift velocity between alpha beams and protons,vα,is reduced with the heliocentric distance,but the ratio of vαto vA(the local Alfven velocity)does not vary obviously and has a typical velocity ratio of vα/vA≤1.The alpha beam instability is believed to be responsible for the deceleration of alpha beams in the solar wind.However,the role of the temperature anisotropy of ions(protons and alpha particles)on the alpha beam instability has not been examined.Based on the kinetic theory of the PDRK solver,this study systemically investigates the alpha beam instability in the presence of proton and alpha temperature anisotropies and considers the effects of these temperature anisotropies on the instability at an arbitrary propagation angle relative to the ambient magnetic field.It is found that the real frequencies,growth rates and threshold conditions of the excited waves sensitively depend on the proton temperature anisotropy T_(i⊥)/T_(i‖)and the alpha temperature anisotropy T_(α⊥)/T_(α‖),as well as the parallel electron betaβe‖.In particular,for both alpha beam and proton temperature anisotropy driven cases,the parallel magnetosonic/whistler(PM/W),backward magnetosonic/whistler(BM/W)and oblique Alfvén/ion cyclotron(OA/IC)waves arise when T_(i⊥)/T_(i‖)<1,and the PM/W,OA/IC,parallel Alfven/ion cyclotron(PA/IC)and mirror waves occur when T_(i⊥)/T_(i‖)>1.The presence of anisotropic protons leads to a lower velocity threshold for the OA/IC and BM/W waves at T_(i⊥)/T_(i‖)<1 and for the OA/IC,PA/IC and mirror waves at T_(i⊥)/T_(i‖)>1.For both alpha beam and alpha temperature anisotropy driven cases,the PM/W and OA/IC waves are unstable when T_(α⊥)/T_(α‖)<1,and the PM/W,OA/IC,PA/IC,oblique magnetosonic/whistler(OM/W)and mirror waves are likely to grow as T_(α⊥)/T_(α‖)>1.The presence of anisotropic alpha particles results in a lower threshold velocity for the PM/W wave at T_(α⊥)/T_(α‖)<1 and for the PA/IC,OM/W and mirror waves

关 键 词：(Sun:)solar wind Sun:heliosphere waves 

分 类 号：P353.8[天文地球—空间物理学] P182[天文地球—地球物理学]