March 1, 2013, 12:00 pm - 1:00 pm
March 1, 12:00 pm - 1:00 pm
Theory of Flux-Rope CMEs: Dynamics of CMEs and Ejecta Magnetic Field at 1 AU
James Chen, NRL
It has been shown that the erupting flux rope (EFR) model of CMEs can correctly reproduce observed CME trajectories from the Sun to 1 AU using STEREO data. For a number of events where both the trajectory (position-time) data and in situ CME ejecta magnetic field data, B(1 AU), are available, it has been shown that the best-fit solutions constrained by the position-time data alone produce magnetic field strength in agreement with the in situ data (Kunkel and Chen 2010). Furthermore, the best-fit solutions predict an electromotive force (i.e., electric field) whose temporal profiles, determined by flux injection, are in close agreement with those of the associated GOES SXR light curves (Chen and Kunkel 2010). In this talk, I will discuss the quantitative physics underlying the the EFR theory and its correspondence to the observed data. In particular, it is shown how quantitative information such as physical scales, temporal profiles of SXR data, and magnetic field at 1 AU can be derived from the observed position-time data alone, with good agreement with available data of other quantities. This provides evidence that the EFR equations of motion, which are based on ideal MHD, correctly capture magnetic structure of CMEs, the forces acting on them, and the relationship between the macroscopic fluid dynamics and magnetic field. It is significant that the EFR theory provides a consistent set of equations that can be driven entirely by position-time data to correctly calculate magnetic field at 1 AU and temporal profiles of the SXR data. More recent work has investigated the quantitative dependence of B (1 AU) on solar parameters based on the EFR model (Kunkel, PhD thesis, 2012; Kunkel, Chen, and Howard, 2013). It is shown that the magnetic field strength at 1 AU most primarily depends on the total amount of magnetic energy injected via poloidal flux injection but not on the functional form of the flux injection. In addition, the footpoint separation distance of the initial equilibrium flux rope is found to be a critically important scale affecting both the initial acceleration and B(1 AU).