Observation Research Of Plasma Waves And Particle Dynamics In The Near-Sun Solar Wind

In solar-terrestrial space plasmas,various quasi-monochromatic waves,which are locally detected by satellites,are closely related to particle dynamics.On the one hand,quasi-monochromatic waves are generally produced by unstable particle velocity distribution.On the other hand,quasi-monochromatic waves can also affect the particle dynamics behavior through wave-particle interactions.Hence,the study of plasma waves and particle dynamics has been receiving much attention in the community of solarterrestrial space physics.Before 2018,the direct detection for the near-Sun solar wind(below 0.3 AU)and the solar atmosphere was not available,only the remote technology could provide the information of plasma waves,which were further used to conjecture indirectly the micro dynamics of particles.Since 2018,the Parker Solar Probe(PSP)had performed in-situ detection for the near-Sun solar wind and extended solar corona,leading to the direct observational research of plasma waves and particle dynamics in such space environment.The research is becoming the advanced and hot subject in communities of solar and solar wind physics.The near-Sun solar wind is the early period of the formation of the solar wind,which contains magnetic field structures and transient events with different characteristic scales that can significantly affect plasma waves and particle dynamics wherein.Based on PSP observations,this thesis carries out the study of plasma waves and particle dynamics in the near-Sun solar wind,especially paying attention on plasma fluctuations and particle dynamical behavior in special magnetic field structures and transient events.The first chapter will introduce the particle velocity distributions in the solar wind and the instability mechanism contributing to shaping these distribution,and this chapter will also introduce previous works of ion-scale waves and related ion dynamics as well as electron-scale waves and related electron dynamics in the near-Sun solar wind.The second chapter will introduce the two instruments suited on the PSP,i.e.,FIELDs and SWEAP,that are used to study plasma waves and particle dynamics,and this chapter will also introduce normal technology and method for dealing observational data.The third chapter will present two research works on ion-scale waves and related ion dynamics in the near-Sun solar wind.For the small-scale flux rope(SFR)and intermittent structures that are frequently detected in the near-Sun solar wind,this chapter performs the event identification and wave analysis by using PSP observations,and this chapter then gives a comprenensive analysis for two typical events.The first work focuses on ion-scale waves in the SFR.This work identifies an SFR event with medium Alfvenicity by using PSP observations,in which the event lasting time is about 11 minutes and the event location is around 0.23 AU.Through the wave analysis,quasi-monochromatic ion-scale waves with the duration of about 2-3 minutes are detected both the leading and trailing regions.Their frequencies are generally higher than the local proton cyclotron frequency,and their polarization behaves the left-handed polarization.In order to distinguish the nature of the wave mode of observed waves,an effective antenna length method is developed,in which the information of observed electromagnetic fluctuations and the knowledge of the basic plasma wave theory are used to estimate the effective antenna length relating the PSP electric field measurement.This work finds that only the ion-cyclotron wave can lead to a reasonable prediction of the effective antenna length,and thus,the observed waves are identified as ion-cyclotron waves propagating outward from the Sun.Consequently,this work provides either the observational evidence of existence of the SFR with medium Alfvénicity in the nearSun solar wind for the first time,or the observational evidence of ion-cyclotron waves in the SFR for the first time.Since the plasma instrument only detects a minor part of the three-dimensional proton velocity distribution in this event,it is difficult to perform quantitative analysis of wave-particle interactions.Through the qualitative analysis for the proton velocity distribution,this work proposes that the observed waves seem to be generated close to the Sun,not locally excited.The second work focuses on ion-scale waves in interplanetary discontinuity.This work identifies a special discontinuity event based on the PSP,which resides at about 0.16 AU.Owing to the observed features of magnetic field,plasma parameter and shock Mach number,this event is suggested to be a slow shock.Ion-scale waves arise in both upstream and downstream.However,the upstream and downstream waves have distinctly different observational features:the former is left-handed polarized,and the latter is dominated by right-handed polarized waves,and there also exist left-handed polarized waves.The proton energy distributions in the upstream and downstream regions are different.Moreover,through the analysis of the proton velocity distribution,this work shows that both the upstream and downstream proton populations consist of proton core and beam components,but the plasma parameters of the two proton components are obviously different.Using the fitted parameters of the proton core and beam components,the instability analysis shows that the ion-cyclotron wave is triggered in upstream,and both fast-magnetosonic wave and ion-cyclotron wave are excited in downstream,which can qualitatively interpret the observed ion-scale waves.In addition,this work explores the physical process of the proton velocity distribution modulated by ion-scale waves through wave-particle interactions based on the analysis of the energy transfer rate between the waves and protons.The fourth chapter presents the research work on electron-scale waves and related electron dynamics.This work finds the existence of a new type of plasma waves in the near-Sun solar wind by using PSP observations,which arise around the heliospheric current sheet.They have significant electric field perturbations,but they seem to have no magnetic field perturbations.The wave frequencies are much larger than the proton cyclotron frequency,which correspond to the wave characteristic scale being the electron scale.These waves exhibit multi frequency bands,and there are two frequency distributions:one is that the multiband are narrow,in which the wave frequencies are smaller than the electron cyclotron frequency;the other is the multiband frequencies larger than the electron cyclotron frequency.These two waves are named as "f<fce multi-narrowband electrostatic waves" and "f>fce multi-band electrostatic waves",respectively.Here,f and fce denote the wave frequency and electron cyclotron frequency,respectively.In the f<fce multi-narrowband electrostatic wave event,the bicoherence technique is used to analyze nonlinear wave-wave interactions,and it shows that nonlinear wave-wave interactions are the dominant mechanism responsible for the formation of multi-band waves.In f>fce multiband electrostatic wave event,these waves are modulated by ion-scale waves,and their electric field perturbations have corresponding periodic variations.For the wave mode nature,the nature of f<fce multi-narrowband electrostatic waves is uncertain,and both the oblique ion acoustic wave and lower-hybrid wave are possible.The nature of f>fce multiband electrostatic waves is the electron Bernstein mode wave.Owning to that the intensity of these waves is not positively correlated with the angle between the magnetic field and the solar wind velocity,this does not support the condition for the excitation of high-frequency electrostatic waves resulting from the satellite wake effect.Through the analysis of the electron velocity distribution in the presence of the observed waves,it finds that the f<fce multi-narrowband electrostatic waves may generated by electron beam.For the f>fce multiband electrostatic wave,this work estimates the energy of resonant electrons based on information of the observed waves and the wave-particle resonance condition,and the estimated energy is consistent with the typical energy of the two electron beam components and the temperature anisotropy component.Thus,the observed high-frequency wave can effectively interact with these electron components.Chapter 5 will summarize the main findings and also provide the discussion on future research work.This thesis exhibits that various magnetic field structures and transient events are closely related to the excitation of the plasma waves in the near-Sun solar wind,and it also provides more observational features of the plasma waves and accompanying particle dynamics therein.These results promote a more comprehensive understanding for early phase of the evolution of the solar wind.