Connecting Speeds, Directions and Arrival Times of 22 Coronal Mass Ejections From the Sun to 1 Au

Abstract

Forecasting the in situ properties of coronal mass ejections (CMEs) from remote images is expected to strongly enhance predictions of space weather and is of general interest for studying the interaction of CMEs with planetary environments. We study the feasibility of using a single heliospheric imager (HI) instrument, imaging the solar wind density from the Sun to 1 AU, for connecting remote images to in situ observations of CMEs. We compare the predictions of speed and arrival time for 22 CMEs (in 2008CMEs (in -2012 to the corresponding interplanetary coronal mass ejection (ICME) parameters at in situ observatories (STEREO PLASTIC/IMPACT, Wind SWE/MFI). The list consists of front-and backsided, slow and fast CMEs (up to 2700 km s −1 ). We track the CMEs to 34.9 ± 7.1 deg elongation from the Sun with J maps constructed using the SATPLOT tool, resulting in prediction lead times of −26.4 ± 15.3 hr. The geometrical models we use assume different CME front shapes (fixed-Φ, harmonic mean, self-similar expansion) and constant CME speed and direction. We find no significant superiority in the predictive capability of any of the three methods. The absolute difference between predicted and observed ICME arrival times is 8.1 ± 6.3 hr (rms value of 10.9 hr). Speeds are consistent to within 284 ± 288 km s −1 . Empirical corrections to the predictions enhance their performance for the arrival times to 6.1 ± 5.0 hr (rms value of 7.9 hr), and for the speeds to 53 ± 50 km s −1 . These results are important for Solar Orbiter and a space weather mission positioned away from the Sun-Earth line.

COMPARISON BETWEEN 2D AND 3D PARAMETERS OF 306 FRONT-SIDE HALO CMEs FROM 2009 TO 2013

“…To understand and forecast these disturbances in interplanetary (IP) space caused by CMEs, it is essential to obtain their three-dimensional (3D) parameters, such as speed, width, and propagation direction (Taktakishvili et al 2009;Lugaz et al 2011;Jang et al 2014;Lee et al 2014;Möstl et al 2014).…”

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

“…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.…”

“…They employed different extrapolations of the height-time trajectory of the CME front beyond a heliocentric distance of 50 R and achieve a prediction of the shock arrival time near 1 AU within ±13 h for the entire event set, and within ±6 h for the seven (78%) best predictions. Along the same lines, Möstl et al (2014) extrapolated the height-time trajectories of 22 CME-ICME fronts in heliospheric images. They obtained a prediction error of ICME speeds of about 250-300 km s À1 , a prediction error of ICME arrival time of 1-7 h and an absolute prediction error of 7-8 h, depending on the method used.…”

“…The combination with heliospheric imaging makes it possible to track CMEs from the Sun to the Earth (e.g. Rouillard 2011;Colaninno et al 2013;Möstl et al 2014) and, as a consequence, to develop and validate new prediction techniques (e.g. Gopalswamy et al 2013).…”