Sun-to-Earth Characteristics of the 2012 July 12 Coronal Mass Ejection and Associated Geo-Effectiveness

Abstract

We analyze multi-spacecraft observations associated with the 2012 July 12 Coronal Mass Ejection (CME), covering the source region on the Sun from SDO, stereoscopic imaging observations from STEREO, magnetic field characteristics at MESSENGER, and type II radio burst and in situ measurements from Wind. A triangulation method based on STEREO stereoscopic observations is employed to determine the kinematics of the CME, and the outcome is compared with the result derived from the type II radio burst with a solar wind electron density model. A Grad-Shafranov technique is applied to Wind in situ data to reconstruct the flux-rope structure and compare it with the observation of the solar source region, which helps understand the geo-effectiveness associated with the CME structure. Conclusions are as follows: (1) the CME undergoes an impulsive acceleration, a rapid deceleration before reaching MESSENGER, and then a gradual deceleration out to 1 AU, which should be noticed in CME kinematics models; (2) the type II radio burst was probably produced from a high-density interaction region between the CME-driven shock and a nearby streamer or from the shock flank with lower heights, which implies uncertainties in the determination of CME kinematics using solely type II radio bursts; (3) the flux-rope orientation and chirality deduced from in situ reconstruction at Wind agree with those obtained from solar source observations; (4) the prolonged southward magnetic field near the Earth is mainly from the axial component of the largely southward inclined flux rope, which indicates the importance of predicting both the flux-rope orientation and magnetic field components in geomagnetic activity forecasting.

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

“…Later, Lugaz et al (2010) and Liu et al (2010b) incorporated a harmonic mean (HM) approximation, which assumes that the CME front is a sphere attached to the Sun and tangent to the lines of sight of the two spacecraft. The triangulation concept has proved to work well in acquiring CME interplanetary kinematics and in connecting remote sensing observations with in situ signatures (e.g., Liu et al 2010aLiu et al ,b, 2013Liu et al , 2016Lugaz et al 2010;Möstl et al 2010;Harrison et al 2012;Davies et al 2013;Hu et al 2016). The triangulation technique with Fβ and HM approximations is detailed and discussed in Liu et al (2010bLiu et al ( , 2013Liu et al ( , 2016.…”

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

“…The GCS model can acquire the heliocentric distances of the CME leading front and has been successfully applied to SOHO and STEREO imaging observations (e.g., Thernisien et al 2009;Liu et al 2010;Cheng et al 2013;Mishra et al 2015). The frequency drift of type II radio bursts produced by CME-driven shocks can be converted to radial distances using a proper solar wind density model (e.g., Reiner et al 2007;Liu et al 2008Liu et al , 2013Cremades et al 2015;Hu et al 2016). Using the electron density model of 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 type II burst observations and find general consistency with those derived from triangulation techniques based on STEREO imaging observations.…”

Structure, Propagation, and Expansion of a Cme-Driven Shock in the Heliosphere: A Revisit of the 2012 July 23 Extreme Storm

“…Shock distances inverted from type II bursts have been compared with coronagraph observations near the Sun (e.g., Reiner et al 2007;Liu et al 2008Liu et al , 2009a) and more recently with wide-angle heliospheric imaging data from STEREO over essentially the entire Sun-Earth distance (Liu et al 2013). In addition to the distances, the radio observations may also give clues on type II radio source locations with respect to the CMEs in combination with imaging data (e.g., Martinez-Oliveros et al 2012;Feng et al 2012;Hu et al 2016). In general, they are not widely used as the images because not much information on the shock structure can be inferred from type II bursts.…”