Variability of natural whistler-mode emissions in the inner magnetosphere

Whistler-mode electromagnetic waves, especially natural emissions of chorus and hiss, have been shown to transfer energy between different electron populations in the inner magnetosphere via quasi-linear or nonlinear wave particle interactions. Average or median intensities of chorus and hiss emissions have been found to increase with increasing levels of geomagnetic activity but their stochastic variations in individual spacecraft measurements at the same location are usually comparable to these large-scale temporal effects. Statistical properties of variations of wave power directly influence results of quasi-linear diffusion models.

We use the survey measurements of the Waves instruments of the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) onboard two Van Allen Probes to asses the probability distribution function of these stochastic variations. We take advantage of the entire data set of these measurements with a nearly 100% coverage from August 31, 2012 till October 13, 2019 (2600 days) for spacecraft A, and from  September 1, 2012 till July 16, 2019 (2510 days) for spacecraft B.