Observations of Radiation Belt Losses Due to Cyclotron Wave-Particle Interactions

Electron loss to the atmosphere plays a critical role in driving dynamics of the Earths Van Allen radiation belts and slot region. This is a review of atmospheric loss of radiation belt electrons caused by plasma wave scattering via Doppler-shifted cyclotron resonance. In particular, the focus is on observational signatures of electron loss, which include direct measurements of precipitating electrons, measured properties of waves that drive precipitation, and variations in the trapped population resulting from loss. We discuss wave and precipitation measurements from recent missions, including simultaneous multi-payload observations, which have provided new insight into the dynamic nature of the radiation belts

The Scientific Foundations of Forecasting Magnetospheric Space Weather

The magnetosphere is the lens through which solar space weather phenomena are focused and directed towards the Earth. In particular, the non-linear interaction of the solar wind with the Earth's magnetic field leads to the formation of highly inhomogenous electrical currents in the ionosphere which can ultimately result in damage to and problems with the operation of power distribution networks. Since electric power is the fundamental cornerstone of modern life, the interruption of power is the primary pathway by which space weather has impact on human activity and technology. Consequently, in the context of space weather, it is the ability to predict geomagnetic activity that is of key importance. This is usually stated in terms of geomagnetic storms, but we argue that in fact it is the substorm phenomenon which contains the crucial physics, and therefore prediction of substorm occurrence, severity and duration, either within the context of a longer-lasting geomagnetic storm, but potentially also as an isolated event, is of critical importance. Here we review the physics of the magnetosphere in the frame of space weather forecasting, focusing on recent results, current understanding, and an assessment of probable future developments.Peer reviewe

Explaining the dynamics of the ultra-relativistic third Van Allen radiation belt

Since the discovery of the Van Allen radiation belts over 50 years ago, an explanation for their complete dynamics has remained elusive. Especially challenging is understanding the recently discovered ultra-relativistic third electron radiation belt. Current theory asserts that loss in the heart of the outer belt, essential to the formation of the third belt, must be controlled by high-frequency plasma wave–particle scattering into the atmosphere, via whistler mode chorus, plasmaspheric hiss, or electromagnetic ion cyclotron waves. However, this has failed to accurately reproduce the third belt. Using a data driven, time-dependent specification of ultra-low-frequency (ULF) waves we show for the first time how the third radiation belt is established as a simple, elegant consequence of storm-time extremely fast outward ULF wave transport. High-frequency wave–particle scattering loss into the atmosphere is not needed in this case. When rapid ULF wave transport coupled to a dynamic boundary is accurately specified, the sensitive dynamics controlling the enigmatic ultra-relativistic third radiation belt are naturally explaine

Utilizing AI to unveil the nonlinear interplay of convection, drift, and diffusion on galactic cosmic ray modulation in the inner heliosphere

Abstract Galactic Cosmic Rays (GCRs) are charged particles, originating from galactic and/or extra-galactic Supernova Remnants (SNR), that continuously permeate the Heliosphere. The GCRs are modulated in the heliosphere by convection by solar wind (SW), drift via gradients and curvatures in the Heliospheric Magnetic Field (HMF), diffusion from fluctuations in the HMF, and adiabatic cooling in the expanding SW. An improved understanding of their modulation is imperative as studies on the variations in solar activity levels and solar eruptions in the past rely heavily on the relationship between their modulation and formation of the secondary particles in the Earth’s atmosphere. Here, for the first time, we utilize an AI method, Light Gradient Boosting Machines (LightGBM), to investigate the nonlinear interplay among the modulation processes in different timescales. Our study indicates that the nonlinear interplay among the mechanisms responsible for the GCR modulation in the inner heliosphere are not limited to the scenario of “drift-dominated solar minimum” versus “diffusion-dominated solar maximum”, instead they have dynamic behavior displaying variations in time and in timescales. This study also demonstrates the value of using AI methods to investigate non-linear physical processes in Space Physics in the era of big data

Energetic particle flux measurements from the Korean space weather monitor particle detector: a comparative study with the MPS-HI onboard GOES-16

Abstract The Korean space weather monitor (KSEM) aboard the GEO-KOMPSAT-2A (GK2A) has been continuously measuring energetic particle flux in geostationary orbit at 128.2°E longitude since July 2019. The particle detector (PD) component of KSEM comprises six particle telescopes viewing different directions that provide near-real-time electron flux observations within the energy range of 100 keV to 3.8 MeV. The KSEM PD on the GK2A satellite, together with the MPS-HI on the GOES-16 satellite 156.6° away, can provide valuable simultaneous observations of the asymmetric space environment and contributes to our understanding of this dynamic region. In this study, we present recent energetic electron flux measurements obtained from the KSEM PD and conduct preliminary cross-comparisons with data from the Magnetosphere Particle Sensor–High (MPS-HI) PD, which is part of the SEISS instrument suite onboard GOES-16. The inter-comparisons show that the electron fluxes of the two detectors are in reasonable similarity except for some energy bands under quiet conditions. Additionally, we provide a brief overview of the electron flux responses of both KSEM PD and MPS-HI under enhanced space environment conditions, which shows differences based on sensor characteristics and satellite location. Graphical Abstrac

Discovery of the action of a geophysical synchrotron in the Earth’s Van Allen radiation belts

Although the Earth’s Van Allen radiation belts were discovered over 50 years ago, the dominant processes responsible for relativistic electron acceleration, transport and loss remain poorly understood. Here we show evidence for the action of coherent acceleration due to resonance with ultra-low frequency waves on a planetary scale. Data from the CRRES probe, and from the recently launched multi-satellite NASA Van Allen Probes mission, with supporting modelling, collectively show coherent ultra-low frequency interactions which high energy resolution data reveals are far more common than either previously thought or observed. The observed modulations and energy-dependent spatial structure indicate a mode of action analogous to a geophysical synchrotron; this new mode of response represents a significant shift in known Van Allen radiation belt dynamics and structure. These periodic collisionless betatron acceleration processes also have applications in understanding the dynamics of, and periodic electromagnetic emissions from, distant plasma-astrophysical systems