# Do force drifts occur in highly collisional plasmas

• chandrahas
In summary, the force drifts of guiding centers in a magnetic field can occur in cold plasma, but only in the collisionless case. In a partially ionized plasma with a mean free time shorter than the gyro frequency, this effect may not be observed. In highly collisional plasmas, the drift behaves as if there is no magnetic field, and in intermediate cases, the drift is at a 45 degree angle from both the electric and electric field. This is often used in modeling the ionosphere.
chandrahas
I've read on wikipedia that the force drifts of the guiding centers off particles in a magnetic field also occurs in cold plasma. But does it occur in a cold plasma (Partially Ionized ) in which the mean free time is less than the gyro frequency time?

I thought that the drift were present because of the asymmetry in the gyration. In order to observe this effect, the orbit has to be completed. At least partially. But if the mean free time is smaller than the time required to complete an orbit we wouldn't be observing this effect would we?

To sum it all up: Do force drift occur in Partially Ionized plasmas in which the mean free time is much smaller than the time of gyration?

Thanks

Delta2
As you guessed, the guiding center drifts derived in the collisionless case do not apply if there are collisions. In order to properly include collisions, we usually look for stationary solutions of a multi-fluid model with explicit collision terms.

This approach is used to model the ionosphere, which is highly collisional at low altitudes and weakly collisional at high altitudes.

It turns out that the highly collisional plasma essentially behaves as if there is no magnetic field. For example, consider a plasma with a DC electric field perpendicular to a DC magnetic field. In the highly collisional case the particles drift parallel to the electric field. In the collisionless case you get the standard ##\mathbf{E \times B}## drift. In the intermediate case the drift is in some direction betwen those two extremes; when the collision frequency equals the gyrofrequency the drift is exactly 45 degrees from both ##\mathbf{E}## and ##\mathbf{E \times B}##.

Jason

## 1. Do force drifts occur in highly collisional plasmas?

Yes, force drifts can occur in highly collisional plasmas. Force drifts refer to the movement of particles in a plasma due to the presence of an external force, such as an electric or magnetic field. These drifts can occur even in highly collisional plasmas where collisions between particles are frequent and can significantly affect the particle's motion.

## 2. What causes force drifts in highly collisional plasmas?

Force drifts in highly collisional plasmas can be caused by external forces, such as electric or magnetic fields, or by collisions between particles. These forces can affect the motion of particles in a plasma, causing them to drift in a particular direction.

## 3. How do force drifts affect plasma behavior?

Force drifts can significantly affect the behavior of a plasma by altering the particle's motion and distribution. This can impact the plasma's stability, energy confinement, and transport properties. Force drifts can also play a role in the development of instabilities and turbulence in the plasma.

## 4. Can force drifts be controlled or mitigated in highly collisional plasmas?

Yes, force drifts can be controlled or mitigated in highly collisional plasmas. This can be achieved by adjusting the external fields or by controlling the plasma's collisionality. For example, in fusion plasmas, magnetic fields can be used to control particle motion and reduce the effects of force drifts.

## 5. Are force drifts important for plasma research and applications?

Yes, force drifts are essential for understanding and predicting the behavior of plasmas in various research and industrial applications. They play a crucial role in plasma stability, energy confinement, and transport, and their effects must be considered in plasma modeling and experiments.

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