Energetic electron precipitation due to gyroresonant interactions in the magnetosphere Involving coherent VLF waves with slowly varying frequency

Abstract

A test particle simulation model (Inan et al., 1982) of the gyroresonance wave‐particle interaction in the magnetosphere is extended to study the transient particle precipitation fluxes induced by various coherent VLF waves with slowly varying frequency propagating along the earth's magnetic field lines. For moderate wave intensities (Bw ≤ 10 pT at L = 4) a comparison between input signals with linearly rising and falling frequencies shows that they induce the same amount of precipitated particle energy deposition. However, when the wave growth near the principal interaction region is considered, the precipitation induced by a riser is considerably higher than that induced by a faller. The effect of the frequency‐time slope (df/dt) of the input signal on the induced precipitation energy flux is found to be small. Our results indicate, however, that the precipitation energy flux depends strongly on the falloff in energy of the trapped particle distribution function. The model is applied for computing the transient precipitation energy fluxes induced by a triggered rising emission, a hooklike signal and a one‐hop whistler. The total precipitated energy deposition for these various signals is found to be comparable to that induced by a linear ramp having the same input wave energy density.