Abstract
Abstract. Three existing models of Interplanetary Coronal Mass Ejection (ICME) transit between the Sun and the Earth are compared to coronagraph and in situ observations: all three models are found to perform with a similar level of accuracy (i.e. an average error between observed and predicted 1AU transit times of approximately 11h). To improve long-term space weather prediction, factors influencing CME transit are investigated. Both the removal of the plane of sky projection (as suffered by coronagraph derived speeds of Earth directed CMEs) and the use of observed values of solar wind speed, fail to significantly improve transit time prediction. However, a correlation is found to exist between the late/early arrival of an ICME and the width of the preceding sheath region, suggesting that the error is a geometrical effect that can only be removed by a more accurate determination of a CME trajectory and expansion. The correlation between magnetic field intensity and speed of ejecta at 1AU is also investigated. It is found to be weak in the body of the ICME, but strong in the sheath, if the upstream solar wind conditions are taken into account. Key words. Solar physics, astronomy and astrophysics (flares and mass ejections) – Interplanetary physics (interplanetary magnetic fields; sources of the solar wind)
Highlights
Coronal mass ejections (CMEs) are known to be the major cause of severe geomagnetic disturbances, often referred to as space weather (e.g. Daglis, 2001; etc.)
We have examined models for the prediction of Interplanetary Coronal Mass Ejection (ICME) arrival time at 1 AU that use as input the CME speed at the Sun
The models show a surprising similarity in the average error in ICME arrival time
Summary
Coronal mass ejections (CMEs) are known to be the major cause of severe geomagnetic disturbances, often referred to as space weather (e.g. Daglis, 2001; etc.). The major cause of deceleration in the interplanetary medium is likely to be the interaction of the ICME with the ambient plasma In reality, this will be a complex collection of processes involving shock waves, generation of turbulence, etc., but these are often parameterised as an aerodynamic drag force of the form ACD(V − W )|V − W |, where V is the speed of the centre of mass of the ICME, W is the solar wind speed, CD is a drag coefficient, typically a number of order unity (Chen, 1989, 1996; Cargill et al, 1995, 1996) and A is the cross section of the ICME.
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