Update from the BU-CME Group: Accurate Prediction of CME Deflection and Magnetic reconnection in the interior of interplanetary CMEs
Abstract
The accurate prediction of the path of coronal mass ejections (CMEs) plays an important role in space weather forecasting, and knowing the source location of the CME does not always suffice. During solar minimum, for example, polar coronal holes (CHs) can deflect high latitude CMEs toward the ecliptic plane and when CHs extend to lower latitudes deflections in other directions can occur. To predict whether a CME will impact Earth the effects of the solar background on the CME's trajectory must be taken into account. Here we develop a model (Kay et al. 2013), called ForeCAT (Forecasting a CME's Altered Trajectory), of CME deflection close to the Sun where magnetic forces dominate. Given the background solar wind conditions, the launch site of the CME, and the properties of the CME (such as its mass and size), ForeCAT predicts the deflection of the CME as well as the full trajectory as the CME propagates away from the Sun. For a magnetic background where the CME is launched from an active region located in between a CH and streamer region the strong magnetic gradients cause a deflection of 39.0o in latitude and 21.9o in longitude. Varying the CME's input parameters within observed ranges leads to deflections predominantly between 36.2o and 44.5o in latitude and between 19.5o and 27.9 in longitude. For all cases, the majority of the deflection occurs before the CME reaches a radial distance of 3 R⊙. Recent in situ observations of interplanetary mass ejections (ICMEs) found signatures of reconnection exhausts in their interior or trailing edge. This result suggests that the internal magnetic field reconnects with itself. To this end, we propose an approach (Fermo et al. 2013) borrowed from the fusion plasma community. Taylor (1974) showed that the lowest energy state corresponds to one in which \grad × B = λ B. Variations from this state will result in the magnetic field trying to re-orient itself into the Taylor state solution, subject to the constraints that the toroidal flux and magnetic helicity are invariant. In tokamaks, the result is a sawtooth crash. In an ICME, if we likewise treat the flux rope as a toroidal flux tube, any variation from the Taylor state will result in reconnection within the interior of the flux tube, in accord with the observations by Gosling et al. (2007). We present MHD and PIC simulations that shows that indeed this is the case and discuss the implications for ICMEs.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2013
- Bibcode:
- 2013AGUSMSH23B..02O
- Keywords:
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- 7513 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Coronal mass ejections;
- 7526 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Magnetic reconnection;
- 7954 SPACE WEATHER / Magnetic storms