Propagation Characteristics of Two Coronal Mass Ejections from the Sun Far into Interplanetary Space

Abstract

Propagation of coronal mass ejections (CMEs) from the Sun far into interplanetary space is not well understood, due to limited observations. In this study we examine the propagation characteristics of two geo-effective CMEs, which occurred on 2005 May 6 and 13, respectively. Significant heliospheric consequences associated with the two CMEs are observed, including interplanetary CMEs (ICMEs) at the Earth and Ulysses, interplanetary shocks, a long-duration type II radio burst, and intense geomagnetic storms. We use coronagraph observations from SOHO/ LASCO, frequency drift of the long-duration type II burst, in situ measurements at the Earth and Ulysses, and magnetohydrodynamic propagation of the observed solar wind disturbances at 1 au to track the CMEs from the Sun far into interplanetary space. We find that both of the CMEs underwent a major deceleration within 1 au and thereafter a gradual deceleration when they propagated from the Earth to deep interplanetary space, due to interactions with the ambient solar wind. The results also reveal that the two CMEs interacted with each other in the distant interplanetary space even though their launch times on the Sun were well separated. The intense geomagnetic storm for each case was caused by the southward magnetic fields ahead of the CME, stressing the critical role of the sheath region in geomagnetic storm generation, although for the first case there is a corotating interaction region involved.

Quantifying the Propagation of Fast Coronal Mass Ejections from the Sun to Interplanetary Space by Combining Remote Sensing and Multi-point In Situ Observations

“…By comparing the speeds of 11 ICMEs observed both at the Earth and Ulysses, Richardson (2014) argues that fast CMEs with a higher speed than that of the ambient medium slowly decelerate beyond 1 au, which is consistent with the suggestion of Liu et al (2013). Combining coronagraph observations, interplanetary type II radio bursts, and in-situ measurements at the Earth and Ulysses, Liu et al (2008Liu et al ( , 2017 and Zhao et al (2017) find that a fast CME/shock finished its major deceleration within 1 au and thereafter moved with a roughly constant speed. As far as we know, there are few statistical analyses of CME/shock propagation from the Sun to the Earth and then beyond 1 au using coordinated coronagraph observations, type II bursts, and in-situ measurements.…”

“…As remote signatures of CME-driven shocks, they drift to lower frequencies as the shocks propagate away from the Sun. The frequency associated with the type II radio burst can be converted to the CME/shock propagation distance based on a suitable solar wind density model (e.g., Chertok & Fomichev 1976;Reiner et al 2007;Liu et al 2008Liu et al , 2013Liu et al , 2017Cremades et al 2015;Hu et al 2016;Zhao et al 2017). Using an electron density model (Leblanc et al 1998, referred to as the Leblanc density model hereafter), Liu et al (2013) obtain the radial distances of CME-driven shocks from the associated type II bursts, which are consistent with the results from wide-angle stereoscopic imaging observations.…”

Characteristics of a Gradual Filament Eruption and Subsequent CME Propagation in Relation to a Strong Geomagnetic Storm

“…We use a graduated cylindrical shell (GCS) model proposed byThernisien et al (2006) to fit the CME based on running-difference coronagraph images from STEREO A/COR2and SOHO/LASCO. The GCS model can determine the direction of propagation, tilt angle of CME flux rope and height (e.g.,Thernisien et al 2009;Liu et al 2010b;Hu et al 2017;Zhao et al 2017).Application of the model gives an average propagation direction of about 13 • west of the Sun-Earth line and 6 • north, which is consistent with the location of the flare ribbons (W12 • N17 • ). The speed of the CME leading edge is accelerated from ∼70 km s −1 at 4.4 R ⊙ to ∼370 km s −1 at 16.2 R ⊙ (see below).…”

Propagation and Interaction Properties of Successive Coronal Mass Ejections in Relation to a Complex Type II Radio Burst

“…The kinematic model can also be used to describe the propagation of the CME driver, as has been demonstrated in previous studies (e.g., Gopalswamy et al 2001a;Reiner et al 2007;Liu et al 2008;Zhao et al 2017). The shock is not a freely propagating shock but gains energy continuously from the CME, despite a concern on the standoff distance between the shock and driver.…”

“…The frequency drift results from the decrease of the ambient plasma density when the shock moves away from the Sun. Therefore, a type II burst is usually used to derive the shock propagation distance by assuming a density model (e.g., Reiner et al 2007;Liu et al 2008Liu et al , 2009aFeng et al 2012;Hu et al 2016;Zhao et al 2017). Type II emissions are also used to study CME-CME interactions, a typical signature of which is an increase in the bandwidth and intensity of the type II burst (Gopalswamy et al 2001b).…”