Speaker: Sergei Kamaletdinov
Affiliation: EPSS, UCLA

Abstract:
The dynamics of energetic electron fluxes in Earth’s radiation belts are conventionally described by two dominant mechanisms: (1) wave–particle resonant interactions, resulting in acceleration and pitch-angle scattering, and (2) radial diffusion driven by ultra-low-frequency (ULF) waves. However, observations often reveal behavior that cannot be fully explained by these processes, indicating the need for additional radial transport mechanisms beyond classical diffusion. Indeed, radial transport can arise even in the absence of waves, solely due to the topology of magnetic field lines. This mechanism is known as Drift-Orbit Bifurcation (DOB), which occurs on the dayside, where solar wind compression splits the equatorial magnetic field minimum into two off-equatorial minima, violating the second adiabatic invariant and enabling radial transport. While previous studies have primarily considered symmetric magnetic field configurations, we conduct a detailed investigation of realistic DOB under north–south and east–west asymmetries introduced by the IMF direction and dipole tilt angle. We find that such asymmetric configurations produce large jumps—of the order of the adiabatic invariant itself—in the second adiabatic invariant. Moreover, we show that these jumps closely correspond to the so-called geometric jumps well known in Hamiltonian systems theory. Using a Hamiltonian framework and large-scale guiding-center simulations, we show that these jumps can drive substantial radial transport within a single drift period. We discuss the implications of this new radial transport mechanism in the context of energetic electron transport near the magnetopause. These results shed new light on observations of isolated enhancements of >30 keV electrons, as observed by equatorial spacecraft (THEMIS) as well as low-orbit spacecraft such as CubeSats (ELFIN/CIRBE) and POES.

Zoom/Meeting Link: https://ucla.zoom.us/j/97828298609?pwd=kbJEOQ2YHlxZifxQW1uT7SQkiBmchT.1

Submitted by: Omar abuassaf (oabuassaf@epss.ucla.edu)