Tracking the momentum flux of a CME and quantifying its influence on geomagnetically induced currents at Earth

摘要

We investigate a CME propagating towards Earth on 29 March 2011. This eventis specifically chosen for its predominately northward directed magnetic field,so that the influence from the momentum flux onto Earth can be isolated. Wefocus our study on understanding how a small Earth-directed segment propagates.Mass images are created from the white-light cameras onboard STEREO which arealso converted into mass height-time maps (mass J-maps). The mass tracks onthese J-maps correspond to the sheath region between the CME and its associatedshock front as detected by in situ measurements at L1. A time-series of massmeasurements from the STEREO COR-2A instrument are made along the Earthpropagation direction. Qualitatively, this mass time-series shows a remarkableresemblance to the L1 in situ density series. The in situ measurements are usedas inputs into a 3D magnetospheric space weather simulation from CCMC. Thesesimulations display a sudden compression of the magnetosphere from the largemomentum flux at the leading edge of the CME and predictions are made for thetime-derivative of the magnetic field (dB/dt) on the ground. The predicteddB/dt were then compared with observations from specific equatorially-locatedground stations and show notable similarity. This study of the momentum of aCME from the Sun down to its influence on magnetic ground stations on Earth ispresented as preliminary proof of concept, such that future attempts may try touse remote sensing to create density and velocity time-series as inputs tomagnetospheric simulations.