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.

Turbulence is an important mechanism for energy conversion in weakly collisional plasmas. In fluid turbulence, energy injected into the system at large spatial scales is transferred to smaller scales until it is dissipated as heat through collisions. In the interim between energy injection and dissipation, kinetic effects can also mediate the dissipation of energy below characteristic fluid (ion) scales. There is a longstanding question concerning plasmas with low collisional rates: How does this energy conversion process end without collisions? In addition, this classical understanding of turbulence is, in nature, based on a velocity-averaged theory of Vlasov-Boltzmann systems. The energy in consideration is that of the plasma bulk motion; the transfer process is one through space. Since a Vlasov-Boltzmann description concerns both space and velocity, we can also ask the question: Is there a conjugate spatial-averaged theory of turbulence, one that describes a turbulent energy transfer instead through velocity?
In this talk, we explore these two questions regarding turbulence in space and in velocity with MMS observations in two regions in the Earth’s magnetosphere. In the magnetotail, explosive large-scale magnetic reconnection generates strong turbulence with low density and background field. The electromagnetic field spectra are well resolved below electron scales, suitable for turbulence studies of kinetic effects. We show evidence of a sub-electron kinetic range where the energy transfer process appears to complete. In the magnetosphere, the distribution function is well resolved with MMS instruments, suitable for turbulence studies of fine structures in velocity space near fluid scales. We show the first ever statistical observation of velocity-space cascade using data from the MMS unbiased magnetosheath campaign