Fig. 4From: Nonlinear triggering process of whistler-mode emissions in a homogeneous magnetic fieldTime evolution of a magnetic field amplitude, b spectrum with instantaneous frequency (Case 1) and c spectrum with instantaneous frequency (Case 2) observed at \(x=204.8\ c\Omega _e^{-1}\). In b and c, magenta dotted lines indicate the instantaneous frequencies. Arrows t1–t4 in b correspond to \(t = 760,\ 829,\ 1717,\) and \(1826\ \Omega _e^{-1}\), respectivelyBack to article page