Investigation Of Solar Energetic Particle Release And Distribution Using Multi-Point Imaging And In Situ Observations

Various processes associated with solar activity have great influences on the so-cial and economic aspects of our modern civilization.A solar energetic particle(SEP)event is one of the main types of the release of solar energy and mass during solar eruptions,and it is also one of the most huge space weather hazards.It is of critical important to understand the particle distribution,acceleration,release and transport for space weather research and forecasting.In this dissertation,based on remote imaging and in situ observations from multi-point spacecraft,we investigate the properties of large SEP events including the particle release,propagation,distribution and associa-tions with other physical phenomena during solar eruptions.The SEP event associated with an extreme solar storm,which has wide distribu-tions and high particle intensities,could lead to a serious impact on human technological society.We study the SEP event associated with the 2012 July 23 extreme solar storm,for which STEREO and the spacecraft near Earth provide remote sensing and in situ ob-servations.We examine the particle intensities,proton anisotropy,element abundance ratios,magnetic connectivity and spectra using the observations.Conclusions are as follows:the particle distribution is related to the expansion of the shock;the coronal mass ejection(CME)and shock observed by STEREO B are not associated with the extreme solar storm,and they are from another eruption but influence the transport and distribution of the particles associated with the extreme solar storm;the properties of the spectra are associated with the shock acceleration efficiency and the relative location between the shock and the spacecraft.The roles of the associated EUV wave and shock during the release of particles are still under debate.The solar eruption on 2012 January 27 resulted in a wide-spread SEP event which was accompanied by an X-class flare,extreme-ultraviolet(EUV)wave and fast CME.Based on the remote sensing and in situ observations from STEREO and the near-Earth spacecraft,we trace the propagation of the EUV wave in the corona,fit the shock structure using an ellipsoid shock model and investigate the magnetic con-nectivity between the spacecraft and the EUV wave and the shock during the particle release.Conclusions are as follows:(1)the CME,shock and SEP event associated with this eruption were observed by STEREO A and the near-Earth spacecraft.The release of particles observed by STEREO A is later than the particle release at the near-Earth spacecraft;(2)The EUV wave propagated outward from the active region along differ-ent directions.The propagation of the EUV wave were affected by active regions and coronal holes and then became diffuse.The EUV wave failed to arrive at the magnetic footpoint of STEREO A or the near-Earth spacecraft during the particle release;(3)Our shock fitting shows that the release time of the particles observed at L1 was consistent with the time when the shock first established contact with the magnetic field line con-necting the near-Earth spacecraft.The release of the particles observed by STEREO A was delayed relative to the time when the shock was initially connected to STEREO A via the magnetic field line.We suggest that the particle acceleration efficiency of the portion of the shock connected to the spacecraft determines the release of energetic particles at the spacecraft.Ground Level Enhancement(GLE)events form a particular case of high-energy SEP events associated with GeV protons.These events have fewer occurrences in the solar activities but pose huge space weather hazard.We study the GLE event associ-ated with the solar eruption on 2017 September 10.Using the remote sensing and in situ observations,we fit the CME and the shock,analyze the properties of the parti-cle distribution,composition and spectra.We also examine shock properties during the particle release.Conclusions are as follows:(1)The CME and shock underwent an impulsive acceleration and then a gradual deceleration during the initial eruption.The apparent acceleration of the shock was largely dominated by the expansion due to the ejecta internal overpressure;(2)The GLE event had a wide distribution in the space.Both the near-Earth spacecraft and STEREO A observed high particle intensities.There was little flare particles in the near-Earth observations and the particles observed at the near-Earth spacecraft were mainly accelerated by the shock.The flare particles may not be released in the part connected to the near-Earth spacecraft;(3)The shock accelera-tion was efficient with different acceleration mechanisms at the initial stage.Particles could be accelerated to high energies in the lower corona.The novelty and uniqueness of this dissertation are as follows:(1)Based on un-precedented multi-point in situ observations,we analyze the properties of the particle propagation,distribution and spectra during the SEP events.This work gives impor-tant clues for understanding the particle transport and distribution as well as the space weather forecasting model;(2)Combined unprecedented multi-point high cadence re-mote sensing and in situ observations,we study the propagation of EUV wave and the properties of shock kinematics,and reveal the correlation between the particle release and the other physical phenomena including the EUV wave and the shock.This work is of crucial important for building the space weather modeling;(3)We study the proper-ties of the shock during the particle release and the connectivity between the shock and the spacecraft using unprecedented combination of multi-point(including remote sens-ing and in situ)observations and shock modeling.We reveal the influences of the shock properties for the particle release,which have important implications for investigating the particle acceleration.