A prediction model for the global distribution of whistler chorus wave amplitude developed separately for two latitudinal zones

Abstract

Whistler mode chorus waves are considered to play a central role in accelerating and scattering electrons in the outer radiation belt. While in situ measurements are usually limited to the trajectories of a small number of satellites, rigorous theoretical modeling requires a global distribution of chorus wave characteristics. In the present work, by using a large database of chorus wave observations made on the Time History of Events and Macroscale Interactions during Substorms satellites for about 5 years, we develop prediction models for a global distribution of chorus amplitudes. The development is based on two main components: (a) the temporal dependence of average chorus amplitudes determined by correlating with the preceding solar wind and geomagnetic conditions as represented by the interplanetary magnetic field (IMF) Bz and AE index and (b) the determination of spatial distribution pattern of chorus amplitudes, specifically, the profiles in L in all 2 h magnetic local time zones, which are categorized by activity levels of either the IMF Bz or AE index. Two separate models are developed: one based only on the IMF Bz and the other based only on AE. Both models predict chorus amplitudes for two different latitudinal zones separately: |magnetic latitude (MLAT)| < 10°, and |MLAT| = 10°-25°. The model performance is measured by the coefficient of determination R2 and the rank-order correlation coefficient (ROCC) between the observations and model prediction results. When tested for a new data interval of ∼1.5 years, the AE-based model works slightly better than the IMF Bz-based model: for the AE-based model, the mean R2 and ROCC values are ∼0.46 and ∼0.78 for |MLAT| < 10°, respectively, and ∼0.4 and ∼0.74 for |MLAT| = 10°-25°, respectively; for the IMF Bz-based model, the mean R2 and ROCC values are ∼0.39 and ∼0.74 for |MLAT| < 10°, respectively, and ∼0.33 and ∼0.70 for |MLAT| = 10°-25°, respectively. We provide all of the model information in the text and supporting information so that the developed chorus models can be used for the existing outer radiation belt electron models.