Plasmoid-induced-reconnection and fractal reconnection

By Kazunari Shibata, S. Tanuma. 2001

336 citations recorded by the source corpus.

As a key to understanding the basic mechanism for fast reconnection in solar flares, plasmoid-induced-reconnection and fractal reconnection are proposed and examined. We first briefly summarize recent solar observations that give us hints on the role of plasmoid (flux rope) ejections in flare energy release. We then discuss the plasmoid-induced-reconnection model, which is an extention of the classical two-ribbon-flare model which we refer to as the CSHKP model. An essential ingredient of the new model is the formation and ejection of a plasmoid which play an essential role in the storage of magnetic energy (by inhibiting reconnection) and the induction of a strong inflow into reconnection region. Using a simple analytical model, we show that the plasmoid ejection and acceleration are closely coupled with the reconnection process, leading to a nonlinear instability for the whole dynamics that determines the macroscopic reconnection rate uniquely. Next we show that the current sheet tends to have a fractal structure via the following process path: tearing ⇒ sheet thinning ⇒ Sweet-Parker sheet ⇒ secondary tearing ⇒ further sheet thinning ⇒ ⋯. These processes occur repeatedly at smaller scales until a microscopic plasma scale (either the ion Larmor radius or the ion inertial length) is reached where anomalous resistivity or collisionless reconnection can occur. The current sheet eventually has a fractal structure with many plasmoids (magnetic islands) of different sizes. When these plasmoids are ejected out of the current sheets, fast reconnection occurs at various different scales in a highly time dependent manner. Finally, a scenario is presented for fast reconnection in the solar corona on the basis of above plasmoid-induced-reconnection in a fractal current sheet.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/ab570054201b8bf6353c5125f0a07e9b9dc4d97b

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Citations in the corpus

A MAGNETIC RECONNECTION MECHANISM FOR ION ACCELERATION AND ABUNDANCE ENHANCEMENTS IN IMPULSIVE FLARES (2009, background): “…remains unknown although models based on particle interaction with multiple magnetic islands in two dimension (Matthaeus et al. 1984; Kliem 1994; Shibata & Tanuma 2001) and three dimension (Onofri et al. 2006) and with magnetohydrodynamic waves (Miller 1998; Petrosian & Liu 2004) have been…”
SIMULTANEOUS OBSERVATION OF RECONNECTION INFLOW AND OUTFLOW ASSOCIATED WITH THE 2010 AUGUST 18 SOLAR FLARE (2011, background): “To transcend this scale gap, Shibata & Tanuma (2001) suggested the fractal reconnection model.”
Downflow Motions Associated with Impulsive Nonthermal Emissions Observed in the 2002 July 23 Solar Flare (2004, background): “Therefore, the correlations between plasmoid ejections, or downflow, and HXR bursts represent a plasmoid-induced, nonsteady reconnection (Shibata 1999; Shibata & Tanuma 2001).”
Observations of Turbulent Magnetic Reconnection within a Solar Current Sheet (2018, background): “If the current sheet is fragmented into magnetic islands of different sizes (Shibata & Tanuma 2001), different reconnection rates and thus different kinetic energies of the outflow jets can be achieved.”
Nanoflare Statistics from First Principles: Fractal Geometry and Temperature Synthesis (2002, methodology): “This process of fractal reconnection has recently also been described with an analytical model (Shibata & Tanuma 2001).”
Ion heating resulting from pickup in magnetic reconnection exhausts (2009, methodology): “for these energetic ions remains unknown although models based on particle interaction with multiple islands in 2-D [Matthaeus et al., 1984; Kliem, 1994; Shibata and Tanuma, 2001] and 3-D [Onofri et al.”
Particle acceleration and kinematics in solar flares – A Synthesis of Recent Observations and Theoretical Concepts (Invited Review) (2002, background): “Recent work describes the topology of reconnection in multiple magnetic islands with a fractal geometry (Shibata and Tanuma, 2001).”
NUMERICAL TESTS OF FAST RECONNECTION IN WEAKLY STOCHASTIC MAGNETIC FIELDS (2009, background): “Shibata & Tanuma (2001) extended the concept suggesting that tearing may result 8 These effects will usually be small compared to effect of a broad outflow zone containing both plasma and ejected shared magnetic flux.”