This research team will determine the mechanisms responsible for plasma heating during coronal mass ejections (CMEs), by performing a time-dependent ionization analysis of CMEs observed by the Atmospheric Imaging Assembly (AIA) instrument on the Solar Dynamics Observatory (SDO) spacecraft. In their data analysis, the team will quantitatively constrain plasma heating to low solar altitudes where most of the heating occurs, apply plasma density diagnostics, and then assess a wide range of models with different plasma heating parameterizations and rates, in order to determine how much heating is required to match AIA observations.
The research team will then test the three most promising candidate heating mechanism theories, which are (1) heating by the large-scale post-eruption current sheet, (2) small-scale magnetic reconnection events during flux rope expansion and relaxation, and (3) energetic particles. The proposing team will use three-dimensional simulations of CMEs to predict the observational signatures of plasma heating by the current sheet, which will help elucidate whether or not CME current sheets are energetically important to CME eruptions. The team will also perform simulations of an expanding cylindrical flux rope to determine the relationship between magnetic reconnection and relaxation, as well as to determine the spatial and temporal dependence of plasma heating. In addition, they will perform simulations of energetic particles contained within expanding flux ropes in realistic geometries, in order to determine whether there is enough time for non-thermal particles to heat CME plasma before its density drops.
Results from this project will be published in widely available peer reviewed journals. Since CMEs are significant drivers of space weather, this research on the early evolution of CMEs can also improve space weather forecasts. This research team will be applying a legacy numerical code developed by the laboratory plasma physics community to an important problem in solar physics. In this way, the team will strengthen interdisciplinary ties between these two communities while serving the research interests of both. Components of this project will be performed by undergraduate summer interns who are separately funded by the NSF through a solar physics Research Experience for Undergraduates (REU) program at the Harvard-Smithsonian Center for Astrophysics. This undergraduate cadre will include members of traditionally underrepresented groups in science.
