Understanding local loss processes in Earth’s radiation belts is critical to understanding their overall structure. Electromagnetic ion cyclotron waves can cause rapid loss of multi-MeV electrons in the radiation belts and contribute to an uncommon three-belt structure in the radiation belts. These loss effects have been observed at a range of L* values, recently as low as L* = 3.5. Here, we present a case study of an event where a local minimum develops in multi-MeV electron phase space density near L* = 3.5 and evaluate the possibility of EMIC waves in contributing to the observed loss feature. Signatures of EMIC waves are shown including rapid local loss and pitch angle bite outs. Analysis of the wave power spectral density during event shows EMIC wave occurrence at higher L* values. Using these representative wave parameters, we calculate minimum resonant energies, diffusion coefficients, and simulate the evolution of electron PSD during this event. From these results, we find that O+ band EMIC waves could be contributing to the local loss feature during this event. O+ band EMIC waves are uncommon, but do occur in these L* ranges, and therefore may be a significant driver of radiation belt dynamics under certain preconditioning of the radiation belts.

Pitch Angle Distributions in the radiation belts are well characterized with sinnα. By tracking the exponent ‘n’, termed Pitch Angle Index, we are able to observe persistent and cross energy changes in pitch angle distributions of Van Allen radiation belt electrons using Van Allen Probes particle observations. The pitch angle distributions measurements are well fit down to a single satellite spin, and therefore can track spatially and temporally confined changes to determine connection between particles and waves. We use the Van Allen Probes data in conjunction with Geostationary Operational Environmental Satellites (GOES) spacecraft and several ground magnetometer stations from Canadian Array for Realtime Investigations of Magnetic Activity (CARISMA) and Finnish pulsation magnetometer network of Sodankylä Geophysical Observatory (SGO) to connect particles that become very anisotropic to electromagnetic ion cyclotron (EMIC) waves during a quiet period over two days, June 26 and 27, 2013. The waves and peaks in the particle PADs are both long lasting but spatially separated, suggesting that wave particle interactions in the inner magnetosphere can occur for extend periods of time and have significant impact on the global radiation belts, even during otherwise geomagnetically quiet times and when wave activity is highly localized.

The Magnetic Pileup Boundary or Induced Magnetosphere Boundary (IMB) has been an enigma in Mars aeronomy. Previously dubbed the planetopause, magnetopause, ion-composition boundary, and protonopause, identification of this unique plasma region has been marked by difficulty. In this case study, we used data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission to identify IMB crossings and configurations during the month of September 2017 with a particular focus on the 10 September 2017 solar events. It was concluded that the ICME had no statistically significant impact on the IMB standoff locations. This study also investigated the effects of upstream dynamic pressure, thermal pressure from the magnetosheath, magnetic pressure from the Magnetic Pileup Region (MPR), thermal pressure associated with the ionosphere, and Extreme Ultraviolet (EUV) irradiance on the IMB during September 2017. We have found that during the 163 IMB crossings, magnetic pressure in the MPR and thermal pressure in the ionosphere had the largest influence on the IMB standoff distance.

Accurate measurements of trapped energetic electron fluxes are of major importance for the studies of the complex nature of radiation belts and the characterization of space radiation environment. The harmonization of measurements between different instruments increase the accuracy of scientific studies and the reliability of data-driven models that treat the specification of space radiation environment. An inter-calibration analysis of the energetic electron flux measurements of the Magnetic Electron Ion Spectrometer (MagEIS) and the Relativistic Electron-Proton Telescope (REPT) instruments on-board the Radiation Belt Storm Probes (RBSP) versus the measurements of the Extremely High Energy Electron Experiment (XEP) unit on-board Arase (ERG) mission is presented. The performed analysis demonstrates a remarkable agreement between the majority of MagEIS and XEP measurements and suggests the re-scaling of MagEIS HIGH unit and of REPT measurements for the treatment of flux spectra discontinuities. The proposed adjustments were validated successfully using measurements from ESA Environmental Monitoring Unit (EMU) on-board GSAT0207 and the Standard Radiation Monitor (SREM) on-board INTEGRAL. The derived results lead to the harmonization of science-class experiments on-board RBSP (2012-2019) and Arase (2017- ) and propose the use of the datasets as reference in a series of space weather and space radiation environment developments.

The Mars Atmosphere and Volatile EvolutionN (MAVEN) spacecraft can act as an intermittent upstream solar wind monitor at ~ 1.5 AU. To inspect the evolution of solar wind turbulence in the Martian exosphere, we have gathered proton (i.e., ionized hydrogen) temperature measurements taken by the Solar Wind Ion Analyzer (SWIA) onboard the MAVEN spacecraft. Here we investigate instabilities driven by the proton temperature anisotropy at Mars. We look at the temperature anisotropy T⊥p/T||p (i.e., the ratio of the perpendicular proton temperature component to the parallel proton temperature component) and the parallel plasma beta, β||p, to determine the active plasma instability mode. Furthermore, we report on the properties of turbulence near Mars’ orbital location during upstream solar wind intervals from January 2015 to December 2016 (~ 1 Martian year). We find that the probability distributions of (β||p, Rp)-values are limited at Rp >1 and Rp <1. We also find evidence of intermittency implying nonlinear, non-homogeneous energy transfer. Additionally, spectral index values near the Kolmogorov scaling value are observed for the inertial range (10-4 Hz to 0.1 Hz).

We investigate the rare events of sudden appearances of relativistic electrons (>700 keV), which are normally confined to the Van Allen belts, in the slot region. The frequency of occurrence of these events are on average 1-2 per year. To cope with the scarcity of events, in this study we examine 21 years of trapped relativistic electron fluxes available from the POES and MetOp Space Environment Monitor (SEM‐2). Our statistical analysis show that these events can occur even during moderate geomagnetic activity. Occurrence of these events correlates with high speed solar winds or ICMEs depending on the phase of the solar cycle. Most importantly, we show that ULF wave activity plays a significant role in causing these events and the events could be predicted in 75% of the cases.

Forecasting relativistic electron fluxes at geostationary Earth orbit (GEO) has been a long term goal of the scientific community, and significant advances have been made in the past, but the relation to the interior of the radiation belts, that is, to lower $L-$shells is still not clear. In this work we have identified 60 relativistic electron enhancement events at GEO to study the radial response of outer belt fluxes and the correlation between the fluxes at GEO and those at lower $L-$shells. The enhancement events occurred between 1 October 2012 and 31 December 2017 and were identified using GOES 15 $>$2 MeV fluxes at GEO, which we have used to characterize the radial response of the radiation belt, by comparing to fluxes measured by the Van Allen probes ECT-REPT between $2.55.0$, and generally similar for $L>4.5$. Post enhancement maximum fluxes show a remarkable correlation for all $L > 4.0$ although the magnitude of the pre-existing fluxes on the outer belt plays a significant role and makes the ratio of pre-to-post enhancement fluxes less predictable in the region $4.0

We present a study analyzing relativistic and ultra relativistic electron energization and the evolution of pitch angle distributions using data from the Van Allen Probes. We study the connection between energization and isotropization to determine if there is a coherence across storms and across energies. Pitch angle distributions are fit with a Jsinθ function, and the variable ‘n’ is characterized as the pitch angle index and tracked over time. Our results show that, consistently across all storms with ultra relativistic electron energization, electrons become most anisotropic within around a day of Dst and relax down to prestorm isotropization levels in the following week. In addition, each consecutively higher energy channel is associated with higher anisotropy after storm main phase. Changes in the pitch angle index are reflected in each energy channel; when 1.8 MeV electrons increase (or decrease) in pitch angle index, so do all the other energy channels. In a superposed epoch study, we show that the peak anisotropies differ between CME- and CIR- driven storms and measure the relaxation rate as the anisotropy falls after the storm. The relaxation rate in pitch angle index for CME-driven storms is -0.14+/-0.023 at 1.8 MeV, -0.28+/-0.01 at 3.4 MeV, and -0.36±0.02 at 5.2 MeV. For CIR-driven storms, the relaxation rates are -0.09±0.01 for 1.8 MeV, -0.12±0.02 for 3.4 MeV, and -0.11±0.02 for 5.2 MeV. This study shows that there is a global coherence across energies and that storm type may play a role in the evolution of electron pitch angle distributions.