Velocity profile of interplanetary coronal mass ejections beyond 1 AU

Abstract

We analyze the dynamics of interplanetary coronal mass ejections (ICMEs) through the interplanetary medium from the lower solar corona to ∼5.3 AU. Our analysis uses a one-dimensional hydrodynamical model derived from the fluid equation of motion that considers an effective drag force under both the laminar and turbulent hypotheses (low and high Reynolds number, respectively). The model has three sets of input parameters. The first set is related to the ICME itself, i. e., initial speed and mass; the second set of parameters is related to the ambient solar wind: density and velocity; and the final set corresponds to the ambient solar wind-ICME interaction: an ICME expansion factor and a viscosity or drag parameter. We use this model to explain the radial dynamics of a particular ICME detected at three different locations: close to the Sun, where the ICME was ejected on 20 January 2004, and detected by the SOHO/LASCO coronagraphs; two days later, at Earth's L1 by the ACE spacecraft (∼1.0 AU), and finally, ∼14 days later, at ∼5.3 AU by the Ulysses spacecraft near Jupiter's orbit. The model is then compared to a general set of ICMEs data from Ulysses that cover distances from ∼1.3 AU to ∼5.3 AU. Our model successfully reproduces the dynamical behavior of ICMEs at distances near Earth's orbit and works reasonably well at larger distances ≈5.3 AU. Therefore, our analysis shows that the ICME-solar wind interaction may be treated as a drag interaction with the appropriate drag factors, not only at distances ≤1 AU, but at larger distances. Finally, we show that our model is useful in identifying ICMEs at different heliocentric distances. Copyright 2011 by the American Geophysical Union.