Research On The Solar Wind-magnetosphere-ionosphere/thermosphere Coupling At Jupiter

As one of the largest and fastest rotating planets in the Solar system,Jupiter has a large and powerful magnetosphere.Unlike the counterparts of terrestrial planets,the dynamics of Jupiter's magnetosphere is dominated by two main mechanisms: one is the solar wind driven “Dungey cycle” which is similar to the Earth's magnetosphere,and the other is the Vasyliunas cycle related to the fast planetary rotation and internal plasma source.The solar wind interaction with the magnetosphere,as well as the magnetospheric dynamics,is one of the key problems in space physics.Driven and modulated by the solar wind and planetary rotation,the characteristics of both the magnetospheric plasma flow and magnetosphere-ionosphere-thermosphere(MIT)coupling mechanism are hot topics in the study of the Jovian magnetosphere.Observational data including in-situ measurements and remote sensing,and simulation tools play a very important role in the study of Jupiter physics.In Chapter 1,we briefly introduce the solar wind and Jupiter,and then review some of the background knowledge of Jupiter's magnetosphere,ionosphere and thermosphere/atmosphere.After that,we further introduce the morphology of Jupiter's aurora and the basic theories of MIT coupling.Magnetohydrodynamic(MHD)numerical models are important tool to study the large-scale physical processes of planetary magnetosphere,it can efficiently simulate the large-scale dynamical processes in the magnetosphere.In order to study the dynamics of Jupiter's global magnetosphere driven by the solar wind and planetary rotation,in Chapter 2,we constructed a new MHD model of the Jovian global magnetosphere,which includes the internal Io plasma source,the fast planetary rotation(? 10 h),and the MIT coupling processes.The simulation results show that our model can reasonably simulate the basic configurations of Jupiter's magnetosphere,such as the equatorial plasmasheet,the corotation driven enforcement currents and ionospheric field-aligned currents(FACs).In addition,we also make a comparison between the simulation results and the observations,and find that the density and pressure distributions of the equatorial magnetosphere are in good agreement with the observation,and the simulated ionospheric FACs distribution is very similar to the observed auroral morphology,which indicates that the two different methods simulating the MIT coupling processes in our model can be used to mimic the general morphology of the main aurora.Solar wind,as one of the important driving sources for the magnetosphere,dominates the global dynamics and physical processes of Jupiter's magnetosphere.Due to the lack of observational data,the real-time solar wind data near Jupiter can only be obtained from numerical models.Therefore,in Chapter 3,we construct a data-driven MHD model for the background solar wind in the inner heliosphere in order to get the solar wind near Jupiter.In this model,we implement the inner boundary conditions derived from a series of empirical relations such as WSA(Wang-Sheeley-Arge)relation with an input of the solar synoptic magnetogram maps.To test the model performance and the prediction accuracy,we compare our simulation results with multi-satellite insitu measurements with different latitudes and different heliocentric distances.The results suggest that:(1)our model can reproduce the typical large-scale structures and physical phenomena of the interplanetary solar wind,such as corotation interaction regions(CIRs),heliospheric current sheet and high-speed streams;(2)there is an overall agreement between our simulated solar wind parameters(including plasma density,velocity,temperature and magnetic field intensity)and the satellite observations at different latitudes with varying heliocentric distances.In this chapter,we demonstrate that our heliospheric model is capable of reproducing the large-scale structures of the solar wind in the inner heliosphere,and the model can be used to predict the background solar wind near planets such as the Earth and Jupiter,which is of great significance to the study of the interaction between the solar wind and the planetary magnetospheres.As mentioned above,the magnetosphere dynamics at Jupiter is dominated by MIT coupling processes.In general,the MIT coupling can be characterized by a set of key parameters in terms of the ionosphere,i.e.,ionospheric conductivity,currents and electric field,particle exchange along magnetic field lines,Joule heating and particle energy deposition.Due to the limitation of MHD theory,many physical phenomena and processes in MIT coupling cannot be described by MHD models.Thus,in Chapter 4,combined with Juno's multi-instrument data,we propose a new method to evaluate the MIT coupling parameters along the Juno's trajectory.We apply it to the main auroral crossing events for Juno's first 8 southern perijoves(i.e.,orbits),so as to analyze the characteristics of these key parameters during the main auroral crossing,and try to establish a global image of Jupiter's MIT coupling.In summary,we have conducted a preliminary study on the solar wind around Jupiter,Jovian magnetosphere,ionosphere and thermosphere as a causal chain.As a result:(1)two MHD models describing the global dynamics of the solar wind and Jupiter's magnetosphere have been constructed;(2)the basic characteristics of Jupiter's MIT coupling have been quantitatively analyzed based on Juno multi-instrument data.