A Sun-to-Earth Analysis of Magnetic Helicity of the 2013 March 17–18 Interplanetary Coronal Mass Ejection

Abstract

We compare the magnetic helicity in the 17-18 March 2013 interplanetary coronal mass ejection (ICME) flux-rope at 1 AU and in its solar counterpart. The progenitor coronal mass ejection (CME) erupted on 15 March 2013 from NOAA active region 11692 and associated with an M1.1 flare. We derive the source region reconnection flux using post-eruption arcade (PEA) method (Gopalswamy et al. 2017a) that uses the photospheric magnetogram and the area under the PEA. The geometrical properties of the near-Sun flux rope is obtained by forward-modeling of white-light CME observations. Combining the geometrical properties and the reconnection flux we extract the magnetic properties of the CME flux rope (Gopalswamy et al. 2017b). We derive the magnetic helicity of the flux rope using its magnetic and geometric properties obtained near the Sun and at 1 AU. We use a constant-α force-free cylindrical flux rope model fit to the in situ observations in order to derive the magnetic and geometric information of the 1-AU ICME. We find a good correspondence in both amplitude and sign of the helicity between the ICME and the CME assuming a semi-circular (half torus) ICME flux rope with a length of π AU. We find that about 83% of the total flux rope helicity at 1 AU is injected by the magnetic reconnection in the low corona. We discuss the effect of assuming flux rope length in the derived value of the magnetic helicity. This study connecting the helicity of magnetic flux ropes through the Sun-Earth system has important implications for the origin of helicity in the interplanetary medium and the topology of ICME flux ropes at 1 AU and hence their space weather consequences.

CME–CME Interactions as Sources of CME Geoeffectiveness: The Formation of the Complex Ejecta and Intense Geomagnetic Storm in 2017 Early September

“…The large spread in the recovered ϕ r values from single-event analyses reflects the different areas covered by the signatures considered (ribbons, dimmings, and PEAs), and we note that large uncertainties affect the estimation of ϕ r , i.e. up to ±50% of the measured value, as reported by various studies (Qiu et al 2007;Temmer et al 2017;Tschernitz et al 2018;Dissauer et al 2018a;Gopalswamy et al 2017;Pal et al 2017). Despite the scatter, the different values recovered can therefore be considered to be consistent within the (large) error bars.…”

Dependence of Coronal Mass Ejection Properties on Their Solar Source Active Region Characteristics and Associated Flare Reconnection Flux

“…It is defined by R 0 = h/(1 + (1/κ) estimated using equation (1) of Thernisien et al (2006). L is the length of CME flux rope approximated as L = Pal et al 2017), where h leg is the height of the CME flux rope legs (see equation (3) of Thernisien et al (2006)) and (π/2 + α) is in radian. B 0 is the axial magnetic field strength of the CME defined by B cme = φ p x 01 /LR 0 (assuming a force-free CME flux rope).…”

Coronal Magnetic Structure of Earthbound CMEs and In Situ Comparison

“…In a force-free magnetic field configuration like a flux rope, the total magnetic helicity is conserved (Woltjer, 1958). Previous studies have suggested that the helicity sign, the total helicity, and the total magnetic flux of an ICME flux rope are related to those of its corresponding source region (e.g., Cho et al, 2013;Hu et al, 2014;Leamon et al, 2004;Möstl et al, 2009;Pal et al, 2017;Qiu et al, 2007). Hence, the property of magnetic helicity conservation can be used to assume that once the flux rope type at the Sun is determined, its chirality is maintained as the CME propagates from the Sun to Earth.…”