Ion Temperature Gradient instability: Difference between revisions

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Hence, if a temperature gradient is aligned with a magnetic field gradient (as occurs in a tokamak), particles in the hotter region will drift further. If there is a perturbation in the temperature gradient, then the difference in drift velocities will create charge separation. The charge separation creates a electric field. This electric field creates an ExB drift which increases the perturbation's amplitude. The positive-feedback nature of this loop leads to exponential growth of the instability.
Hence, if a temperature gradient is aligned with a magnetic field gradient (as occurs in a tokamak), particles in the hotter region will drift further. If there is a perturbation in the temperature gradient, then the difference in drift velocities will create charge separation. The charge separation creates a electric field. This electric field creates an ExB drift which increases the perturbation's amplitude. The positive-feedback nature of this loop leads to exponential growth of the instability.
Note that if the temperature gradient is anti-parallel to the magnetic field gradient, the ExB drift will suppress the perturbation rather than increase it.  This situation occurs on the inner, "good-curvature" side of the tokamak.


See the figure for a graphical explanation.
See the figure for a graphical explanation.


[[File:ITG.png | width=10 | image-width=10]]
[[File:ITG.png]]
 
Note that if the temperature gradient is anti-parallel to the magnetic field gradient, the ExB drift will suppress the perturbation rather than increase it.  This situation occurs on the inner, "good-curvature" side of the tokamak.
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