| 英文摘要: | For a long time, it has been unclear and a matter of debate to what degree electron-kinetic effects play a role for the acceleration and the evolution of the solar wind compared to other processes, such as the dissipation of turbulent fluctuations. For the first time, our observational capabilities, with the unprecedented quality of the solar cycle worth of Wind electron data that we are producing, combined with a theoretical analysis will allow us to quantitatively connect electron thermodynamics in the solar wind and microphysical processes and better determine the role of electrons for the evolution of the solar wind. This 3-year SHINE project is expected to improve present understanding of the physical processes that are relevant for the generation and evolution of the solar wind from a very fundamental plasma-physical perspective based on first principles. It will also provide much needed input for the development of predictive physics-based solar-wind models. Including more accurate description of electron physics in such models will lead to major improvements of our understanding of space-weather processes, the propagation of energetic-particle events, as well as the propagation of cosmic rays throughout the heliosphere.
This 3-year SHINE project describes an integrated research program to study the microphysical processes that regulate the kinetic and non-thermal features of solar wind electrons, like the electron core and halo drifts, and the electron strahl structure. It will investigate the micro-instabilities generated by drifts, heat flux and temperature anisotropy, as well as their contributions to solar wind turbulence. The research will be based on in-situ observations of solar wind electron distribution functions, proton measurements, as well as magnetic field and plasma wave data from the Wind spacecraft. A hot plasma dispersion solver will be used to determine the theoretical thresholds and growth rates of electron-driven micro-instabilities.
The electron microphysical processes addressed in this proposal have a broader application than the interplanetary medium, as they occur in the solar corona, the coronae of other stars and compact astrophysical objects, and in other more exotic environments in the universe such as jets and supernova blast waves. Furthermore, the topic of electron microphysics in the solar wind and in space plasma is one of the primary science focus topics by the heliophysics community in the USA, in particular SHINE. In the past, the project team has convened dedicated sessions at the NSF-funded SHINE Workshops in 2014 and 2015, which have received very positive feedback from the heliophysics community. The investigators plan to continue to lead the focus group and the science discussions to foster more, multi-disciplinary, collaborations within the space physics community, involving theory, numerical simulations, observations and data analysis. As part of this project, they propose a follow-up session at the 2016 SHINE Workshop. This science topic is also of great importance in the preparation of the upcoming NASA mission Solar Probe Plus and ESA mission Solar Orbiter, one of their key science goals being to explore in-situ the fundamental microphysical plasma processes at the origin of the heating of the solar corona, acceleration of the solar wind and the evolution of the heliosphere including CMEs and transients. This research project will foster a close work collaboration between the UC Berkeley and the UNH. It will support two young researchers in early phases of their scientific careers and a graduate student at UC Berkeley. The research and EPO agenda of this project supports the Strategic Goals of the AGS Division in discovery, learning, diversity, and interdisciplinary research. |