Coronal Magnetic Structures, Coronal Mass Ejections

Formation and Evolution of Large-Scale Magnetic Funnels in the Solar Corona

Comments Off on Formation and Evolution of Large-Scale Magnetic Funnels in the Solar Corona 01 May 2016

Abstract

The existence of open coronal magnetic fields with peculiar geometry – large-scale magnetic funnels – can be attributed to three factors: (i) the presence of two or more corona holes of the same polarity (or pseudostreamers – PSs), (ii) specific configurations of closed magnetic field in the low corona up to 1.3 Rs (filament channels) and (iii) the presence of strong active regions in the vicinity of the pseudostreamer. The important property of magnetic funnels is their strongly non-monotonic expansion factor below 2 Rs. The case study presented here is a pseudostreamer near the equator, formed between two isolated coronal holes of the same polarity, and harboring a pair of twin filaments in its base. Following the evolution of these coronal holes we find that the PS topology changes when two coronal holes merged together. Using a potential field source-surface (PFSS) extrapolation to compute the coronal field from photospheric maps (SDO/HMI), we show that the funnel-like geometry of the open magnetic field changes to a regular one with monotonic expansion factor after the merging of coronal holes. The presence of coronal magnetic funnels becomes directly visible when sufficient plasma accumulates inside them: when the plasma density grows to become observable coronal cloud prominences appear in the corona. The plasma suspension at heights of 0.3 Rs coincides with the largest gradients in the field which naturally leads to a diamagnetic hypothesis for the force counteracting gravity. We study the evolution of the funnel-like open fields during several solar rotations and find a direct relation between funnels and the presence of coronal clouds at great heights in the solar corona.

Coronal Mass Ejections

Origins of Non-radial Propagation of Eruptive Solar Events

Comments Off on Origins of Non-radial Propagation of Eruptive Solar Events 01 October 2013

Abstract

We demonstrate that major asymmetries in erupting filaments and CMEs, namely major twists and non-radial motions are typically related to the larger-scale ambient environment around eruptive events. Our analysis of prominence eruptions observed by the STEREO, SDO, and SOHO spacecraft shows that prominence spines retain, during the initial phases, the thin ribbon-like topology they had prior to the eruption. This topology allows bending, rolling, and twisting during the early phase of the eruption, but not before. The combined ascent and initial bending of the filament ribbon is non-radial in the same general direction as for the enveloping CME. However, the non-radial motion of the filament is greater than that of the CME. In considering the global magnetic environment around CMEs, as approximated by the Potential Field Source Surface (PFSS) model, we find that the non-radial propagation of both erupting filaments and associated CMEs is correlated with the presence of nearby coronal holes, which deflect the erupting plasma and embedded fields. In addition, CME and filament motions, respectively, are guided towards weaker field regions, namely null points existing at different heights in the overlying configuration. Due to the presence of the coronal hole, the large-scale forces acting on the CME may be asymmetric. We find that the CME propagates usually non-radially in the direction of least resistance, which is always away from the coronal hole. We demonstrate these results using both low- and high-latitude examples.

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Featured Publications

  2016 (1)
Rapid Reconnection and Field Line Topology. Parker, E.; and Rappazzo, A. In Gonzalez, W.; and Parker, E., editor(s), Astrophysics and Space Science Library, volume 427, pages 181, 2016.
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  2015 (1)
Observations and Analysis of the Non-Radial Propagation of Coronal Mass Ejections Near the Sun. Liewer, P.; Panasenco, O.; Vourlidas, A.; and Colaninno, R. \solphys, 290: 3343-3364. November 2015.
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  2014 (1)
Apparent Solar Tornado-Like Prominences. Panasenco, O.; Martin, S.; and Velli, M. \solphys, 289: 603-622. February 2014.
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