# What is the drift speed for plasma?

• ExoP01
In summary, the problem involves calculating the drift speed, drift orbital period, and current density for 1eV protons and 10eV electrons in a grad-B drift with a particle density of 5 cm^-3. The formula used for drift speed is <V> = [6*E/(qBo*L*Re)](0,35 + 0.15sin(a)), where a is the pitch angle, L is the field line, and Bo is the magnetic field strength at the equatorial plane of Earth. The formula for drift orbital period is Td = 2*pi*L*Re/|V|. The current density for the ring current is unknown and may require additional information. However, the stated energies
ExoP01

## Homework Statement

I need to calculate the drift speed, drift orbital period and current density for 1eV protons and 10eV electrons. The density is 5 cm^-3
The assumption is that it is only a grad-B drift

## Homework Equations

<V> = [6*E/(qBo*L*Re)](0,35 + 0.15sin(a))

## The Attempt at a Solution

For drift speed: I assumed that <V> = [6*E/(qBo*L*Re)](0,35 + 0.15sin(a))
Where a= pitch angle = 90 degrees, L= field line= 5 in this case and Bo is 0.35*10^-4 T for equatorial plane of Earth.
q= elementary charge.
I tried and got a wrong value for the average speed when I calculated for 1 eV (proton), the answer became too small. Where did I do wrong?

For drift orbital period:
The formula is (Td=2*pi*L*Re)/abs(V) from above, bud I need V, so this should be easy

The current density for the ring current: I actually have no idea, maybe a hint from you guys?

thanks!

ExoP01 said:

## Homework Statement

I need to calculate the drift speed, drift orbital period and current density for 1eV protons and 10eV electrons. The density is 5 cm^-3
The assumption is that it is only a grad-B drift

## Homework Equations

<V> = [6*E/(qBo*L*Re)](0,35 + 0.15sin(a))

## The Attempt at a Solution

For drift speed: I assumed that <V> = [6*E/(qBo*L*Re)](0,35 + 0.15sin(a))
Where a= pitch angle = 90 degrees, L= field line= 5 in this case and Bo is 0.35*10^-4 T for equatorial plane of Earth.
q= elementary charge.
I tried and got a wrong value for the average speed when I calculated for 1 eV (proton), the answer became too small. Where did I do wrong?

For drift orbital period:
The formula is (Td=2*pi*L*Re)/abs(V) from above, bud I need V, so this should be easy

The current density for the ring current: I actually have no idea, maybe a hint from you guys?

thanks!
There seems to be some missing information in the problem statement. The B-field is missing, but later one indicates the Earth's magnetic field. The particle density is 5 cm-3. How did one determine L = 5?

Please show the source of the equations, and please show one's work.

I think the problem concerns the "ring current" in the Earth's atmosphere, but the stated energies are rather low.
http://farside.ph.utexas.edu/teaching/plasma/Plasmahtml/node23.html

Last edited:

## What is drift speed in plasma?

Drift speed in plasma refers to the average velocity of charged particles, such as electrons and ions, as they move in response to an electric field. It is a measure of how fast the particles are moving in a particular direction.

## How is drift speed calculated?

Drift speed can be calculated by dividing the average velocity of the particles by the electric field strength. It can also be calculated using the equation: vd = μE, where vd is the drift speed, μ is the mobility of the particles, and E is the electric field strength.

## What factors affect drift speed in plasma?

The drift speed in plasma can be affected by various factors, such as the electric field strength, temperature, density of the plasma, and the type of particles present. Changes in these factors can alter the velocity and direction of the particles' movement.

## Why is drift speed important in plasma research?

Drift speed is an essential concept in plasma research as it helps scientists understand the behavior and dynamics of charged particles in a plasma. It is also used to analyze and predict the properties and behavior of plasma under different conditions.

## How does drift speed differ from thermal velocity in plasma?

While drift speed refers to the average velocity of particles in response to an electric field, thermal velocity refers to the random motion of particles due to their thermal energy. Thermal velocity is dependent on the temperature of the plasma, while drift speed is affected by the electric field strength.

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