Fig. 5
![Fig. 5](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs40623-020-01226-x/MediaObjects/40623_2020_1226_Fig5_HTML.png)
Variations of wave normal angle and \(n_{ \bot }\) as a function of \({{\omega_{p} } \mathord{\left/ {\vphantom {{\omega_{p} } {\omega_{c} }}} \right. \kern-0pt} {\omega_{c} }}\) for the incident wave with \({\omega \mathord{\left/ {\vphantom {\omega {\omega_{c} }}} \right. \kern-0pt} {\omega_{c} }} = 3.5\) and \(\nabla n \bot \vec{B}\), under the condition that Eq. (4) can be satisfied. \(D^{\prime}{ = }\, 0\) at RP