PIC simulations of wave-particle interactions with an initial electron velocity distribution from a kinetic ring current model

• Published in: Journal of atmospheric and solar-terrestrial physics Vol. 177; pp. 169 - 178
• Main Authors: Yu, Yiqun, Delzanno, Gian Luca, Jordanova, Vania, Peng, Ivy Bo, Markidis, Stefano
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01.10.2018; Elsevier
• Subjects: Heliospheric and Magnetospheric Physics; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Realistic non-Maxwellian electron distribution; Wave-particle interactions; Whistler wave generation; Wave-particle interactions; Realistic non-Maxwellian electron distribution; Whistler wave generation
• ISSN: 1364-6826; 1879-1824; 1879-1824
• DOI: 10.1016/j.jastp.2017.07.004

Whistler wave-particle interactions play an important role in the Earth inner magnetospheric dynamics and have been the subject of numerous investigations. By running a global kinetic ring current model (RAM-SCB) in a storm event occurred on Oct 23–24 2002, we obtain the ring current electron distribution at a selected location at MLT of 9 and L of 6 where the electron distribution is composed of a warm population in the form of a partial ring in the velocity space (with energy around 15 keV) in addition to a cool population with a Maxwellian-like distribution. The warm population is likely from the injected plasma sheet electrons during substorm injections that supply fresh source to the inner magnetosphere. These electron distributions are then used as input in an implicit particle-in-cell code (iPIC3D) to study whistler-wave generation and the subsequent wave-particle interactions. We find that whistler waves are excited and propagate in the quasi-parallel direction along the background magnetic field. Several different wave modes are instantaneously generated with different growth rates and frequencies. The wave mode at the maximum growth rate has a frequency around 0.62ωce, which corresponds to a parallel resonant energy of 2.5 keV. Linear theory analysis of wave growth is in excellent agreement with the simulation results. These waves grow initially due to the injected warm electrons and are later damped due to cyclotron absorption by electrons whose energy is close to the resonant energy and can effectively attenuate waves. The warm electron population overall experiences net energy loss and anisotropy drop while moving along the diffusion surfaces towards regions of lower phase space density, while the cool electron population undergoes heating when the waves grow, suggesting the cross-population interactions. •Electron velocity distribution solved in ring current model is used to study wave generation in particle-in-cell code.•Whistler wave characteristics and the impact on ring current electron populations are investigated.•Warm population with a few to tens of keV is responsible for the wave excitation and experiences net energy loss and fast drop of anisotropy.