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

Abstract

Our analysis in Papers I and II (Grechnev et al., 2014, Solar Phys. 289, 289 and 1279) of the 18 November 2003 solar event responsible for the 20 November geomagnetic superstorm has revealed a complex chain of eruptions. In particular, the eruptive filament encountered a topological discontinuity located near the solar disk center at a height of about 100 Mm, bifurcated, and transformed into a large cloud, which did not leave the Sun. Concurrently, an additional CME presumably erupted close to the bifurcation region. The conjectures about the responsibility of this compact CME for the superstorm and its disconnection from the Sun are confirmed in Paper IV (Grechnev et al., Solar Phys., submitted), which concludes about its probable spheromak-like structure. The present paper confirms the presence of a magnetic null point near the bifurcation region and addresses the origin of the magnetic helicity of the interplanetary magnetic clouds and their connection to the Sun. We find that the orientation of a magnetic dipole constituted by dimmed regions with the opposite magnetic polarities away from the parent active region corresponded to the direction of the axial field in the magnetic cloud, while the pre-eruptive filament mismatched it. To combine all of the listed findings, we come to an intrinsically three-dimensional scheme, in which a spheromak-like eruption originates via the interaction of the initially unconnected magnetic fluxes of the eruptive filament and pre-existing ones in the corona. Through a chain of magnetic reconnections their positive mutual helicity was transformed into the self-helicity of the spheromak-like magnetic cloud.

Radio, Hard X-Ray, and Gamma-Ray Emissions Associated with a Far-Side Solar Event

“…As a result, both open and closed structures of these domains become filled with energetic particles as well as cool plasma of the pre-eruptive filament. Related schemes containing a single null point were discussed by Gary and Moore (2004), Masson, Antiochos, and DeVore (2013), Meshalkina et al (2009), Grechnev et al (2013b), and Uralov et al (2014. Stretching a large-scale quadrupole into the solar wind might cause disappearance of the null point.…”

A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. IV. Unusual Magnetic Cloud and Overall Scenario

“…The trend of the velocity in the MC (region B in Figure 2a) is close to a linear one (dotted line), which is an attribute of a self-similar expansion (Low, 1984). Such expansion occurs if all forces affecting the ejecta (magnetic forces, plasma pressure, and gravity; so far we have neglected the aerodynamic drag because its effect is not self-similar) decrease with distance by the same factor (Low, 1982;Uralov, Grechnev, and Hudson, 2005). This condition is satisfied if the polytropic index of the MC gas is γ = 4/3.…”

“…These circumstances were the major reasons that inspired us to undertake a comprehensive analysis of this event presented in our Paper I (Grechnev et al, 2014a), Paper II (Grechnev et al, 2014b), and Paper III (Uralov et al, 2014). The analysis has revealed an extremely complex, unusual solar eruptive event.…”

“…The expansion factor can be reduced either due to larger L 0 (typical of quiescent filaments) or due to smaller L MC , which most likely was the case The contribution of the expansion factor to the geoeffective importance of a solar eruption can probably be responsible for an additional scatter in already loose correlations between parameters of solar eruptions and space weather disturbances (see, e.g., Cliver and Svalgaard, 2004;Yurchyshyn, Hu, and Abramenko, 2005;Chertok et al, 2013). The expansion factor, which can be especially reduced for disconnected MCs, might have probably contributed to such abnormal events as the 13 -14 March 1989 superstorm (Dst = −589 nT) and the one after the Carrington event on 1 September 1859 (Carrington, 1859;Tsurutani et al, 2003); the estimated Dst value was of the order of −850 nT according to Siscoe, Crooker, and Clauer (2006). Previous studies on such events (e.g., Tsurutani et al, 2003;Cliver and Svalgaard, 2004) …”

“…The expansion factor, which can be especially reduced for disconnected MCs, might have probably contributed to such abnormal events as the 13 -14 March 1989 superstorm (Dst = −589 nT) and the one after the Carrington event on 1 September 1859 (Carrington, 1859;Tsurutani et al, 2003); the estimated Dst value was of the order of −850 nT according to Siscoe, Crooker, and Clauer (2006). Previous studies on such events (e.g., Tsurutani et al, 2003;Cliver and Svalgaard, 2004) …”