Orientation of the Magnetic Fields in Interplanetary Flux Ropes and Solar Filaments

Abstract

Coronal mass ejections (CMEs) are often associated with erupting magnetic structures or disappearing Ðlaments. The majority of CMEs headed directly toward the Earth are observed at 1 AU as magnetic cloudsÈthe region in the solar wind where the magnetic Ðeld strength is higher than average and there is a smooth rotation of the magnetic Ðeld vectors. The three-dimensional structure of magnetic clouds can be represented by a force-free Ñux rope. When CMEs reach the Earth, they may or may not cause magnetic storms, alter EarthÏs magnetic Ðeld, or produce the phenomena known as auroras. The geoe †ectiveness of a solar CME depends on the orientation of the magnetic Ðeld in it.Two M-class solar Ñares erupted on 2000 February 17. The second Ñare occurred near a small active region, NOAA Active Region 8872. This eruption was accompanied by a halo CME. However, the February 17 CME did not trigger any magnetic activity when it arrived at the Earth. Another powerful Ñare, on 2000 July 14, was also associated with a halo CME, which caused the strongest geomagnetic activity of solar cycle 23. Using ACE measurements of the interplanetary magnetic Ðelds, we study the orientation of the magnetic Ñux ropes in both sets of magnetic clouds and compare them with the orientation of the solar magnetic Ðelds and disappearing Ðlaments. We Ðnd that the direction of the axial Ðeld and helicity of the Ñux ropes are consistent with those of the erupted Ðlaments. Thus, the geoe †ectiveness of a CME is deÐned by the orientation and structure of the erupted Ðlament and by its magnetic helicity as well. We also suggest that the geoe †ectiveness of a CME can be forecasted using daily full-disk Ha and Y ohkoh images and MDI magnetograms as well.

Flux‐Rope Coronal Mass Ejection Geometry and Its Relation to Observed Morphology

“…However, each of these observed events could be deflected in longitude, to an unknown degree. Based on Webb et al (2000), Krall et al (2006), and Yurchyshyn et al (2006) we conclude that 10 deflections are common and so allow longitudes up to 40 from the limb; the longitudes used in this study are 0 ¼ À57 , À70 , and À83 . To avoid redundant images, latitude and longitude angles are limited to the intersection of the northern, eastern, and Earthward solar hemispheres.…”

The magnetic field in the solar atmosphere

“…The majority of ejecta, including CMEs associated with disappearing filaments (Yurchyshyn et al 2001;Cho et al 2013) or eruptive X-ray loops (Mandrini et al 2005;Zheng et al 2011), propagate away from the Sun in the form of magnetic clouds (MCs) and hence actively carry helicity away. MCs are force-free regions of enhanced magnetic field strength, with the field vector monotonically rotating as they journey with the solar wind.…”

Magnetic Field Configuration Models and Reconstruction Methods for Interplanetary Coronal Mass Ejections

“…The orientation of the ICME as it arrives at Earth is an essential parameter, since it is often used to determine the CME rotation as it propagates in the heliosphere (Yurchyshyn et al, 2001). In addition, knowing precisely the orientation of an ICME is particularly important since the orientation of an ICME is known to be related to its geo-effectiveness (see, for example Zhao and Hoeksema, 1998).…”

“…Complex ICMEs (Complex ejecta), which may result from the interaction of successive CMEs or from the interaction of CMEs with complex solar wind structures and streams (Burlaga, Plunkett, and St. Cyr, 2002;Wang, Ye, and Wang, 2003;Lugaz, Manchester, and Gombosi, 2005). Double rotation within one MC have also been reported from Ulysses (Rees and Forsyth, 2004) and ACE observations (Steed et al, 2011), showing that even isolated ICMEs may produce complex ejecta.…”