(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

The original problem is determining the dispersion relation of an ordinary wave in plasma damped by collisions. That part was easy enough but the next part is to find the damping rate (-Im(ω)) of the wave, assuming k is real and [itex]\nu << \omega[/itex] where [itex]\nu[/itex] is the collision frequency.

2. Relevant equations

I've found the dispersion relation to be:

[itex]\omega^2 - k^2c^2 = \frac{\omega_{pe}^2(1-i\frac{\nu}{\omega})}{(1 + \frac{\nu^2}{\omega^2})}[/itex]

And we are told the damping rate is:

[itex]\gamma = \frac{\omega_{pe}^2\nu}{\omega^2 2}[/itex]

3. The attempt at a solution

Since we want only the negative of the imaginary part:

[itex]\gamma = \frac{\nu\omega_{pe}^2}{\omega^2 (1+\frac{\nu^2}{\omega^2 })}[/itex]

However, I can't think of an approximation that would give me that factor of 1/2. Series expansion or small number approximations don't seem to do it. If anyone has ideas, I'd just like a push in the right direction?

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# Homework Help: Estimating the damping coefficient of a wave assuming a very small ratio

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