Experiments on the ducting of Whistler waves at the LAPTAG high school plasma laboratory

A low density duct$\left( {5\% \le \frac{\delta n}{n}\le 50\% } \right)$ in the quiescent afterglow of an RF plasma (L= 1.5 m, dia = 0.3 m $\left( {30G\le B_{0z} \le 100G} \right)$, $n\simeq 10^{11}$cm$^{\mbox{-3}})$ is formed by biasing a 3 cm diameter grid. Whistler waves are launched with a single loop antenna (1 cm diameter), placed within the duct using a phase-locked tone burst ( $40\le f_{wave} \le 110$ MHz). The vector magnetic field of the whistler waves is measured in a plane with dx=dz =1cm, dt = 0.4 ns along with the local plasma density. The whistlers are observed to propagate within the duct, however waves with a different wavelength and angle of propagation radiate from the duct edge. The ducting is studied as a function of the depth of density minima, width of the density channel, and wave frequency, $\frac{f}{f_{ce} }$ . The results will be compared to computer simulations of a two-dimensional electron MHD model.