Comparison of Magnetic Properties in a Magnetic Cloud and Its Solar Source on 2013 April 11–14

Abstract

In the context of Sun-Earth connection of coronal mass ejections and magnetic flux ropes (MFRs), we studied the solar active region (AR) and the magnetic properties of magnetic cloud (MC) event during April 14-15, 2013. We use in-situ observations from the Advanced Composition Explorer and source AR measurements from the Solar Dynamic Observatory. The MCs magnetic structure is reconstructed from the Grad-Shafranov method which reveals a northern component of the axial field with left-handed helicity. The MC invariant axis is highly inclined to the ecliptic plane pointing northward and is rotated by 117 o with respect to the source region PIL. The net axial flux and current in the MC are comparatively higher than from the source region. Linear force-free alpha distribution (10 −7 − 10 −6 m −1 ) at the sigmoid leg matches the range of twist number in the MC of 1-2 AU MFR. The MFR is non-linear force-free with decreasing twist from the axis (9 turns/AU) towards the edge. Therefore Gold-Hoyle (GH) configuration, assuming a constant twist, is more consistent with the MC structure than the Lundquist configuration of increasing twist from the axis to boundary. As an indication to that, the GH configuration yields better fitting to the global trend of in-situ magnetic field components, in terms of rms, than the Lundquist model. These cylindrical configurations improved the MC fitting results when considered the effect of self-similar expansion of MFR. For such twisting behaviour, this study suggests an alternative fitting procedure to better characterise the MC magnetic structure and its source region links.

Forward Modeling of Coronal Mass Ejection Flux Ropes in the Inner Heliosphere with 3DCORE

“…The magnetic field in 3DCORE consists of circular Gold‐Hoyle flux rope cross sections which have a uniform twist, set in this study at a value of 5 turns/AU (e.g., Hu et al, ). The twist value may also be taken from solar observations (e.g., Vemareddy et al, ), but this is not further pursued here. The MFR has a left‐handed chirality, as derived from solar observations in the previous section.…”

“…The twist value may also be taken from solar observations [e.g. Vemareddy et al 2016] but this is not further pursued here. The MFR has a left-handed chirality, as derived from solar observations in the previous section.…”

The Physical Processes of CME/ICME Evolution

“…Such comparisons of orientation, albeit hampered by some uncertainty, suggest that in many, if not most, cases the total rotation of the CME/ICME remains relatively small. However, as reviewed by Démoulin (2008), cases with total rotations larger than 30°are not uncommon, and very large values of about 120°or more have been reported (e.g., Rust et al 2005;Dasso et al 2007;Liu et al 2008bIsavnin et al 2014;Vemareddy et al 2016).…”

Characteristics of a Gradual Filament Eruption and Subsequent CME Propagation in Relation to a Strong Geomagnetic Storm

“…In addition to deflections, CMEs could rotate during their journey from the Sun to Earth (e.g., Yurchyshyn et al 2007;Liu et al 2010b;Lynch et al 2010;Vourlidas et al 2011). Although a statistical study finds that the tilt angles of CME flux ropes are close to those of the magnetic PILs in the corresponding solar source regions (Marubashi et al 2015), cases with rotations larger than 100 • are reported (e.g., Rust et al 2005;Liu et al 2010b;Vemareddy et al 2016). The strength and duration of the southward magnetic field at 1 AU would change due to deflection and rotation of the CME flux rope, and as a result the geoeffectiveness of CMEs becomes uncertain.…”