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A Modified Model Preparation for Middle Cerebral Artery Occlusion Reperfusion

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Model for incomplete reconnection in sawtooth crashes.

M T Beidler¹, P A Cassak

¹Department of Physics, West Virginia University, Morgantown, West Virginia 26506, USA.

Physical Review Letters

|January 17, 2012

Summary

A new model explains incomplete magnetic reconnection during sawtooth crashes in fusion devices. High pressure core convection and exceeding drift speed thresholds halt reconnection, potentially stabilizing plasma. This has implications for tokamaks like ITER.

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Area of Science:

Plasma Physics
Fusion Energy
Magnetohydrodynamics

Background:

Sawtooth crashes are periodic disruptions in tokamak plasmas.
Incomplete magnetic reconnection during these events is not fully understood.
This phenomenon impacts plasma stability and energy confinement.

Purpose of the Study:

To present a new model for incomplete magnetic reconnection during sawtooth crashes.
To explain the physical mechanisms causing reconnection to shut off prematurely.
To connect this model to observed plasma instabilities and experimental data.

Main Methods:

Development of a theoretical model for reconnection dynamics.
Incorporation of plasma pressure gradients and diamagnetic drift effects.
Proof-of-principle two-fluid simulations.
Comparison of model predictions with experimental data from the Mega Ampere Spherical Tokamak (MAST).

Main Results:

The model shows reconnection inflow convecting the high-pressure core, increasing local pressure gradients.
Reconnection is predicted to cease when diamagnetic drift speed exceeds a threshold.
This cessation explains incomplete reconnection and subsequent magnetic shear relaxation.
Simulations confirm the model's core mechanisms.

Conclusions:

The proposed model provides a plausible explanation for incomplete reconnection in sawtooth crashes.
The findings suggest a link between reconnection dynamics and ideal interchange instabilities.
The model's predictions align with MAST experimental data, indicating broad applicability to tokamaks, including ITER.