Predicting the Arrival Time of Coronal Mass Ejections With the Graduated Cylindrical Shell and Drag Force Model

Abstract

Accurately predicting the arrival of coronal mass ejections (CMEs) at the Earth based on remote images is of critical significance in the study of space weather. In this paper, we make a statistical study of 21 Earth directed CMEs, exploring in particular the relationship between CME initial speeds and transit times. The initial speed of a CME is obtained by fitting the CME with the Graduated Cylindrical Shell model and is thus free of projection effects. We then use the drag force model to fit results of the transit time versus the initial speed. By adopting different drag regimes, i.e., the viscous, aerodynamics, and hybrid regimes, we get similar results, with the least mean estimation error of the hybrid model of 12.9 hours. CMEs with a propagation angle (the angle between the propagation direction and the Sun-Earth line) larger than its half angular width arrive at the Earth with an angular deviation caused by factors other than the radial solar wind drag. The drag force model cannot be well applied to such events. If we exclude these events in the sample, the prediction accuracy can be improved, i.e., the estimation error reduces to 6.8 hours. This work suggests that it is viable to predict the arrival time of CMEs at the Earth based on the initial parameters with a fairly good accuracy. Thus, it provides a method of space weather forecast of 1-5 days following the occurrence of CMEs.

The Physical Processes of CME/ICME Evolution

“…The dotted line denotes the expected proton temperature from the observed speed and Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA). The GCS model is capable of describing a wide range of quantities including the bulk velocity mass distribution and three-dimensional trajectory of the CME (e.g., Shi et al 2015). Figure 3 shows application of the GCS model to the 16 June 2010 CME event, which is a relatively slow CME occurring with the eruption of a quiescent filament.…”

“…The model in this case shows evidence for a variety of physical processes we will discuss in following sections, including super-radial expansion and rotation within the first 5 R . In several examples (e.g., Liu et al 2010b;Vourlidas et al 2011;Nieves-Chinchilla et al 2012;Isavnin et al 2014;Shi et al 2015;Schmidt et al 2016), the GCS model has shown how the early 3-D evolution of CMEs can be well described as magnetic flux ropes that are prone to both deflection and rotation.…”

Microwave radio emissions as a proxy for coronal mass ejection speed in arrival predictions of interplanetary coronal mass ejections at 1 AU

“…The 12 July 2012 event was also discarded because we could not affirm from the microwave profile at 9 GHz that this was gyrosynchrotron emission. We selected 12 more ICME events to increase our sample: six (between 2011 and 2012) from the ISEST catalogue 4 , one from Table 1 in Shi et al (2015) and five (in the years 2013 and 2014) from Table 1 in Mays et al (2015). In addition, the 20 events listed in Table 1 in Gopalswamy et al (2013) were also considered.…”

“…1 in Gopalswamy et al 2013). The speeds resulting from multi-spacecraft modelling by Möstl et al (2014) or Shi et al (2015) are represented by filled blue circles and triangles, respectively. The comparison between predictions, observations and modelling in Figure 5 reveals a large spread of CME speeds derived from different techniques.…”

“…The green inverted triangles show the higher of the two CME speeds measured in the STEREO/ COR2 images by Gopalswamy et al (2013). The blue circles and blue triangles are the speeds resulting from multi-spacecraft modelling by Möstl et al (2014) and Shi et al (2015). The red filled squares denote the speeds found from the microwave fluence by using least squares (LS) fitting.…”