# plasmaFrequency (1d, 2d, 3d)¶

Computes the inverse plasma frequency

## Parameters¶

massDensityIndex (integer, required)
Gives the index of the primitive variable that stores mass density. This is used so that number density can be computed and then plasma frequency calculated.
speciesCharge (float, required)
Charge of the species for which we are computing the plasma frequency.
speciesMass (float, required)
Mass of the species for which we are computing the plasma frequency.
epsilon0 (float, required)
Value of permittivity

## Parent Updater Data¶

The following data structures should be specified to the timeStepRestrictionUpdater (1d, 2d, 3d) that calls the plasmaFrequency Time Step Restriction.

in (string vector, required)
Mass Density (nodalArray, at least 1 component, required)
The mass density of the plasma. The component of the data structure that contains the mass density is specified with the parameter massDensityIndex (see below).

## Example¶

The following block demonstrates plasmaFrequency used in combination with timeStepRestrictionUpdater (1d, 2d, 3d) and cyclotronFrequency (1d, 2d, 3d) to compute the time-step restriction in a plasma:

<Updater twofluidTimeStepRestrictions>
kind = timeStepRestrictionUpdater1d
in = [q]
restrictions = [wpe, wce]
onGrid = domain
courantCondition = 1.0

<TimeStepRestriction wpe>
kind = plasmaFrequency1d
speciesCharge = ELECTRON_CHARGE
speciesMass = ELECTRON_MASS
epsilon0 = 1.0
massDensityIndex = 0
</TimeStepRestriction>

<TimeStepRestriction wce>
kind = cyclotronFrequency1d
speciesCharge = ELECTRON_CHARGE
speciesMass = ELECTRON_MASS
magneticFieldIndexes = [23, 24, 25]
massDensityIndex = 0
</TimeStepRestriction>

</Updater>