A missing dusk-side loss process in the terrestrial electron ring current

Abstract

The Earth’s magnetic field traps charged particles which are transported longitudinally around Earth, generating a near-circular current, known as the ring current. While the ring current has been measured on the ground and space for many decades, the enhancement of the ring current during geomagnetic storms is still not well understood, due to many processes contributing to its dynamics on different time scales. Here, we show that existing ring current models systematically overestimate electron flux observations of 10–50 keV on the nightside during storm onset. By analyzing electron drift trajectories, we show that this systematic overestimation of flux can be explained through a missing loss process which operates in the pre-midnight sector. Quantifying this loss reveals that the theoretical upper limit of loss has to be reached over a broad region of space in order to reproduce the observations. This missing loss may be attributed to inaccuracies in the parameterization of the loss due to chorus wave interactions, combined with the scattering by electrostatic electron cyclotron harmonic waves which is currently not included in ring current models.

Global validation of data-assimilative electron ring current nowcast for space weather applications

“…Without the help of data assimilation, VERB-CS overestimates the electron flux values up to three orders of magnitude at radial distances around 3 . This overestimation can be explained by too long electron lifetimes in the pre-midnight sector, as demonstrated in previous work 40 . To quantify the discrepancies between measurements and simulation results, we calculate a weighted mean absolute logarithmic difference (wMAE) to describe the accuracy of the simulation, while the bias is described by the weighted mean logarithmic difference (wME).…”

“…The numerical grid is set up with 25 grid points for the MLT dimension and 29 points for R , covering the range from 1 to 6.6 . This results in a coarser spatial grid compared to previous studies 40 , 53 , which is necessary to limit the memory requirement of the Kalman filter. The V and K dimensions are divided into 21 and 20 points, respectively, on a logarithmic grid, ensuring that the target energy and pitch angle ranges are defined for all radial distances.…”

Distribution of Seed Electron Phase Space Density Minima in Earth's Radiation Belts

“…Convective transport is an important part of seed electron dynamics. Proper modeling of this population requires advanced simulation that includes convective transport using 4‐D codes (e.g., Aseev et al., 2019; Haas et al., 2023; Shprits et al., 2015), which can change the dynamics of PSD minima formation. Other potentially important processes such as scattering by electron cyclotron harmonic waves, electron holes, and time domain structures (e.g., Fukizawa et al., 2022; Horne et al., 2003; Mozer et al., 2017; Shen et al., 2021; Vasko et al., 2017).…”

PINE-RT: An operational real-time plasmasphere model

“…There has also been extensive effort in developing physics-based models, see e.g., (Bailey et al, 1997;Pierrard and Stegen, 2008;Huba and Krall, 2013;Krall and Huba, 2013;Ridley et al, 2014;Huba et al, 2017;Zhelavskaya et al, 2021;Haas et al, 2023) and (Pierrard et al, 2009) for a review. These models describe the physical processes with dynamical equations, relying on parameters estimated empirically via statistical averages.…”