Global Trends of Cme Deflections Based on Cme and Solar Parameters

Abstract

Accurate space weather forecasting requires knowledge of the trajectory of coronal mass ejections (CMEs), including any deflections close to the Sun or through interplanetary space. Kay et al. (2013) introduced ForeCAT, a model of CME deflection resulting from the background solar magnetic field. For a magnetic field solution corresponding to Carrington Rotation (CR) 2029 (declining phase, April-May 2005), the majority of the CMEs deflected to the Heliospheric Current Sheet (HCS), the minimum in magnetic pressure on global scales. Most of the deflection occurred below 4 R . Here we extend ForeCAT to include a three dimensional description of the deflecting CME. We attempt to answer the following questions: a) Do all CMEs deflect to the magnetic minimum? and b) Does most deflection occur within the first few solar radii ( 4 R )? Results for solar minimum and declining phase CMEs show that not every CME deflects to the magnetic minimum and that the deflection is typically determined below 2 R . Slow, wide, low mass CMEs in declining phase solar backgrounds with strong magnetic field and magnetic gradients exhibit the largest deflections. Local gradients related to active regions tend to cause the largest deviations from the deflection predicted by global magnetic gradients, but variations can also be seen for CMEs in the quiet sun regions of the declining phase CR. We show the torques due to differential forces along the CME can cause rotation about the CME's toroidal axis.

The Deflection of the Cartwheel CME: ForeCAT Results

“…From previous works, CME trajectories are deflected mainly in the low corona (until ∼5 R  ), where the magnetic gradients are the strongest (Kay et al 2013(Kay et al , 2015b. In agreement with theliterature, CME trajectories simulated with ForeCAT deflect toward the heliospheric current sheet (HCS) and away from coronal holes (Cremades & Bothmer 2004;Gopalswamy et al 2009a;Kilpua et al 2009).…”

“…One set of parameters defines the CME shape. The CME flux rope is assumed to have a toroidal shape (Figure 2 in Kay et al 2015b): a and c describe the height and width of the CME, b represents the thickness, and d is the center of the CME's toroidal axis above the surface of the Sun. Since the first data point in the Landi et al (2010) SOHO and STEREO-A data set is so close to the Sun's surface (R 0 =1.1 R  ), we consider the initial CME nose position to bea + b + d=R 0 .…”

“…Forecasting a Coronal Mass Ejection's Altered Trajectory (ForeCAT- Kay et al 2013Kay et al , 2015b) is a model that predicts the CME trajectory as a function of radial distance from the Sun: the CME deflection in latitude and/or in longitude is calculated considering magnetic forces (tension and pressure gradient) from the solar background. CME deflection governed by background magnetic forces is widely accepted in the community (Gopalswamy et al 2009a;Gui et al 2011;Shen et al 2011).…”

“…When observational data close to the Sun's surface are available, these parameters are data-constrained, otherwise they are treated as free parameters and later constrained by simulation-data comparisons. Once the ForeCAT input parameters are fixed, the model predicts the full CME trajectory (deflection, rotation, speed) based on the driving magnetic forces from the solar background (Kay et al 2013(Kay et al , 2015b(Kay et al , 2016.…”

Multi-spacecraft Observations of the Coronal and Interplanetary Evolution of a Solar Eruption Associated with Two Active Regions

“…Previous coronagraph observations suggested that latitudinal deflections of CMEs were controlled by the background coronal magnetic field and the overall flow near solar minimum (MacQueen et al 1986), which was confirmed by the result that CMEs near solar minimum were systematically deflected toward lower latitudes while CMEs during solar maximum could deviate toward either the pole or equator (e.g., Cremades & Bothmer 2004;Kilpua et al 2009). Some CMEs were found to be deflected toward the weak magnetic field region associated with the streamer belt or the heliospheric current sheet (e.g., Xie et al 2009;Kay et al 2013;Liewer et al 2015), while Xie et al (2009) reported that fast CMEs could be deflected away from the streamer belt. The coronal hole with strong open magnetic field is one important factor that can divert a CME (e.g., Gopalswamy et al 2004Gopalswamy et al , 2005Gopalswamy et al , 2009Xie et al 2009;Panasenco et al 2013).…”