Calculating Electron Density: Ionospheric Research

[Tone L]

Homework Statement

I am conducting some research and have come across a problem, it could very well be misunderstanding.
I am trying to calculate electron density N.

Homework Equations

There was given a simple formula F = 9√N ...
where F = critical frequency and N = electron density...
But frequency is in hertz..

The Attempt at a Solution

The units don't work out am I missing something (Ionopsheric calculation is what I am doing)
units should be e-/cm³

 

[TSny]

I suspect the factor of 9 in the formula carries some units.

See https://en.wikipedia.org/wiki/Plasma_oscillation#.27Cold.27_electrons

 

[Tone L]

I suspect the factor of 9 in the formula carries some units.

See https://en.wikipedia.org/wiki/Plasma_oscillation#.27Cold.27_electrons

Beautiful thank you.