THE ROLE OF STREAMERS IN THE DEFLECTION OF CORONAL MASS EJECTIONS: COMPARISON BETWEENSTEREOTHREE-DIMENSIONAL RECONSTRUCTIONS AND NUMERICAL SIMULATIONS

Abstract

On 2009 September 21, a filament eruption and the associated coronal mass ejection (CME) were observed by the Solar Terrestrial Relations Observatory (STEREO) spacecraft. The CME originated from the southern hemisphere and showed a deflection of about 15 • toward the heliospheric current sheet (HCS) during the propagation in the COR1 field of view. The CME source region was near the central meridian, but no on-disk CME signatures could be seen from the Earth. The aim of this paper is to provide a physical explanation for the strong deflection of the CME observed on 2009 September 21. The two-sided view of the STEREO spacecraft allows us to reconstruct the three-dimensional travel path of the CME and the evolution of the CME source region. The observations are combined with a magnetohydrodynamic simulation, starting from a magnetic field configuration closely resembling the extrapolated potential field for that date. By applying localized shearing motions, a CME is initiated in the simulation, showing a similar non-radial evolution, structure, and velocity as the observed event. The CME gets deflected toward the current sheet of the larger northern helmet streamer due to an imbalance in the magnetic pressure and tension forces and finally gets into the streamer. This study shows that during solar minima, even CMEs originating from high latitude can be easily deflected toward the HCS, eventually resulting in geoeffective events. How rapidly they undergo this latitudinal migration depends on the strength of both the large-scale coronal magnetic field and the magnetic flux of the erupting filament.

A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. III. Catastrophe of the Eruptive Filament at a Magnetic Null Point and Formation of an Opposite-Handedness CME

“…They have shown that magnetic reconnection can reverse the twist direction of a flux rope emerging into preexisting fields under the conservation of the total relative magnetic helicity. The complex reconnection of a flux rope with the adjacent field in complex magnetic topology has been also described by, e.g., Lugaz et al (2011), Zuccarello et al (2012), and Masson, Antiochos, and DeVore (2013). Grechnev et al (2008Grechnev et al ( , 2011aGrechnev et al ( , 2013 have found observational evidence of magnetic reconnection between the internal field belonging to the eruptive filament and the preexisting coronal field.…”

The Physical Processes of CME/ICME Evolution

“…This result is consistent with who found a positive correlation with the rate of the deflection and the strength of the magnetic energy density gradient. The intrinsic magnetic polarity of the CME flux rope relative to the background coronal magnetic field determines whether and where the magnetic reconnection can occur and consequently deflects the CME (e.g., see simulation work by Chané et al 2005;Zuccarello et al 2012a;Zhou and Feng 2013). If the CMEs intrinsic field is parallel to the ambient field, the CME deflects equator-ward while when the fields are antiparallel, the CME is likely to deflect poleward (Zhou and Feng 2013).…”

Future capabilities of CME polarimetric 3D reconstructions with the METIS instrument: A numerical test

“…Since the launch of STEREO many other methods have been proposed such as forward modelling (Thernisien et al 2006), analysis of height-time diagrams (Mierla et al 2008), and more recently the ellipsoid model (Schreiner et al 2013). Zuccarello et al (2012) have used the triangulation technique to study the deflection of a CME during its path in the solar corona.…”