IMAGE Radio Plasma Imager (RPI) Daily Dynamic Spectrogram Plot

Collection of RPI Daily Dynamic Spectrogram plots at NASA GSFC, covering complete mission period from 2000-04-21 to 2005-12-18. Dynamic Spectrograms present the time history of natural radio emissions in space between 3 and 1009 kHz while the IMAGE spacecraft orbits the Earth. This operating frequency range was selected by the RPI team to provide an optimal temporal resolution to the wave observations. Each image is a daily plot of the voltage spectral density of received signal (color scale) as function of operating frequency (vertical axis) and time (horizontal axis). Commonly used in the analysis of noise generators, spectral density is a frequency-dependent characteristic that describes how much power is generated by the emission source in a 1 Hz bandwidth. RPI Dynamic Spectograms plot a Voltage Spectral Density, which is root of power spectral density, measured in [V/root-Hz] units. Note that conversion of antenna voltage to electric field strength depends on effective length of receive antennas, and such conversion is not performed here. RPI is capable of detecting input radio emissions above its noise floor of 5 nV/root-Hz, which is determined by the internal white noise of the RPI antenna pre-amplifiers.