Chris Spencer edited Theory.tex  about 10 years ago

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\section{Theory}  \center{Appleton's equation is given by}\[\eta^2=1-\frac{\omega_{pe}^2}{\omega^2\left((1+\frac{i\nu}{\omega})-\frac{\omega_{ce}^2\sin^2\theta}{2\omega^2\left(1-\frac{\omega_{pe}^2}{\omega^2}\right)}\pm\sqrt{\frac{(\omega_{ce}^2\sin^2\theta)^2}{4(1-\frac{\omega_{pe}^2}{\omega^2})}+\frac{\omega_{ce}^2cos^2\theta}{\omega^2}}\right)}\]for an infinite plasma[2]. This describes the index of refraction for a whistler wave where $\eta^2=\left(\frac{kc}{\omega}\right)^2$. $\omega_{pe}$ is the plasma frequency,$\omega_{ce}$ is the electron cyclotron frequency, and $\nu$ is the rate of collisions in the plasma.The angle $\theta$ refers to the angle the waves make with respect to the background magnetic field $B_0$.The first assumption made is that the first experiment's waves are made with $\theta=0$ for waves parallel to $B_0$ and that damping is slight so that $\nu\approx0$.Making these assumptions it is found that Appleton's equation reduces to \[n^2=1-\frac{\omega_{pe}^2}{(\omega+\omega_{ce})(\omega-\omega_{ce})}\]. \[n^2=1-\frac{\omega_{pe}^2}{(\omega+\omega_{ce})(\omega-\omega_{ce})}\].Further assumptions can be made to reduce this equation by noting that $\omega_{ci}>>\omega_{ce}$,$\omega>\omega_{ce}$, and that the wave frequency $\omega$ is less than the \omega_{ce}