Figure 4
Equatorial pitch angle diffusion and the minimum resonant energy of electrons for observed conditions. (a, b) Equatorial pitch angle diffusion as a function of equatorial pitch angle. Each curve is plotted every 1 MeV. Solid curves are the calculation results using observed conditions and dotted curves are for a low geomagnetic field strength and a high electron density. (c, d) Minimum resonant energy as a function of the EMIC wave frequency normalized by the cyclotron frequency of O + ions \({\Omega }_{\mathrm{O}+}\). The yellow rectangle indicates the observed frequency range of the EMIC/Pc1 waves, where \({B}_{0}\) is the geomagnetic field intensity at the magnetic equator and \({N}_{e}\) is the electron density. Red bold curves are the calculation results using observed conditions. Black solid and dotted curves are for the typical values of \({B}_{0}\) and \({N}_{e}\).
