Effect of Linear Interaction and Generation of Sideband in the Magnetosphere

Common view is that non-linear interaction between whistler mode signals from a VLF transmitter and energetic electrons can successfully explain the generation of sideband spacings of 1-30 kHz in the magnetosphere. However, VLF transmitter experiments conducted at Siple show that long keydown signals injected into the magnetosphere often generate sidebands as a result of nonlinear interaction with energetic particles. The spectral characteristics of observed sidebands are quite varied from ~ 2 to 100 Hz, but it bears no simple relationship to the carrier amplitudes. It is shown that such small spacing need wave magnetic field amplitude of 1.5 pT, which is lower than threshold for non-liner amplification. The results indicate that linear amplification is able to explain such sideband spacings.