FORECASTING A CORONAL MASS EJECTION'S ALTERED TRAJECTORY: ForeCAT

Abstract

To predict whether a coronal mass ejection (CME) will impact Earth, the effects of the background on the CME's trajectory must be taken into account. We develop a model, ForeCAT (Forecasting a CME's Altered Trajectory), of CME deflection due to magnetic forces. ForeCAT includes CME expansion, a three-part propagation model, and the effects of drag on the CME's deflection.Given the background solar wind conditions, the launch site of the CME, and the properties of the CME (mass, final propagation speed, initial radius, and initial magnetic strength), ForeCAT predicts the deflection of the CME. Two different magnetic backgrounds are considered: a scaled background based on type II radio burst profiles and a Potential Field Source Surface (PFSS) background. For a scaled background where the CME is launched from an active region located between a CH and streamer region the strong magnetic gradients cause a deflection of 8.1 • in latitude and 26.4 • in longitude for a 10 15 g CME propagating out to 1 AU. Using the PFSS background, which captures the variation of the streamer belt position with height, leads to a deflection of 1.6 • in latitude and 4.1 • in longitude for the control case. Varying the CME's input parameters within observed ranges leads to the majority of CMEs reaching the streamer belt within the first few solar radii. For these specific backgrounds, the streamer belt acts like a potential well that forces the CME into an equilibrium angular position.Recent observational studies show that CMEs can undergo strong deflections close

The Effect of Combined Magnetic Geometries on Thermally Driven Winds. I. Interaction of Dipolar and Quadrupolar Fields

“…They calculate the magnetospheric joule heating on the exoplanets orbiting the M dwarf, finding significant changes to atmospheric properties such as thickness and temperature. Additionally, transient phenomena in the Solar wind such as coronal mass ejections are shown to deflect towards streamer belts (Kay et al 2013). This has been applied to mass ejections around M dwarfs stars (Kay & Opher 2014), and could similarly be applied here using knowledge of the streamer locations from our model grid.…”

The Physical Processes of CME/ICME Evolution

“…The authors presented a theoretical method to account for this effect, which was used statistically by to confirm the deflection toward the magnetic energy minimum. demonstrated this deflection property using the Forecasting CMEs Altered Trajectory (ForeCAT) model (see also Kay et al 2013). This tool propagates CMEs using a drag-based empirical model that takes into account magnetic forces as well as CME expansion.…”

“…3 CME and ICME Deflection 3.1 Characteristics and Causes of CME Deflection CME deflection is the departure from a radial trajectory that commonly occurs with significant in-course changes in direction (e.g., Vandas et al 1996;Wang et al 2004;Lugaz et al 2011;Kay et al 2013Kay et al , 2016. Figure 4 shows a clear example of deflection for the 2 November 2008 event where the CME's change in latitude is obvious when comparing the STEREO-B COR1 to COR2 images.…”

Short-term variability of the Sun-Earth system: an overview of progress made during the CAWSES-II period

“…Defining the background is one of the key inputs needed for understanding CME propagation (see e.g., Roussev et al 2012;Arge et al 2013). However, there are other processes that can significantly affect the propagation of CMEs: CME-CME interaction (see e.g., Gopalswamy et al 2001a;2012c;Temmer et al 2012;Harrison et al 2012;Lugaz et al 2012;Liu et al 2014a;Sterling et al 2014;Temmer et al 2014) and CME deflection by largescale structures such as coronal holes and streamers (Gopalswamy 2010(Gopalswamy , 2009dShen et al 2011;Gui et al 2011;Wood et al 2012;Kay et al 2013;Panasenco et al 2013;Gopalswamy and Mäkelä 2014).…”

“…The empirical relationships established between HSS characteristics and the related geomagnetic activity provides an advance warning of impending CIR storms (Tsurutani et al 2006;Verbanac et al 2011). Coronal holes also deflect CME-driven shocks and CMEs that have important space weather consequences (Gopalswamy 2010(Gopalswamy , 2009dOlmedo et al 2012;Kay et al 2013;Mäkelä et al 2013). The deflection by coronal holes can be so large that CMEs originating from close the disk center of the Sun do not arrive at Earth while the shocks do.…”