Abstract
A study of velocity distribution function in Earth's magnetosphere is conducted using high-resolution measurements from the Magnetospheric Multiscale Spacecraft (MMS). The analysis focuses on the AZ-non-Maxwellian distribution that is a complex velocity-space structure, exhibiting a power-law distribution of moments. By imposing constraints on the spectral indices of the AZ-velocity distribution, the most suitable distribution for modeling Earth's magnetosphere is determined. The combined use of MMS data and analysis of velocity distribution provides new insights into the behavior of plasma particles and the velocity space structures responsible for energy dissipation in plasmas. Understanding particle distribution, behavior, and the influence of cold ions in Earth's magnetosphere is crucial for advancing our knowledge of plasma physics and has practical implications for space weather and magnetospheric dynamics. Addressing the remaining uncertainties and challenges in measurements, analysis of non-Maxwellian distribution of ions is essential for a comprehensive understanding of space plasma environments.