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Energetic electron precipitation leads to increased nitric oxide (NO) production in the mesosphere and lower thermosphere. NO distributions in the wintertime, high‐latitude Southern Hemisphere atmosphere during geomagnetic storms are investigated. NO partial columns in the upper mesosphere at altitudes 70–90 km and in the lower thermosphere at 90–110 km have been derived from observations made by the Solar Occultation For Ice Experiment (SOFIE) on board the Aeronomy of Ice in the Mesosphere (AIM) satellite. The SOFIE NO measurements during 17 geomagnetic storms in 2008–2014 have been binned into selected geomagnetic latitude and geographic latitude/longitude ranges. The regions above Antarctica showing the largest instantaneous NO increases coincide with high fluxes of 30–300 keV precipitating electrons from measurements by the second‐generation Space Environment Monitor (SEM‐2) Medium Energy Proton and Electron Detector (MEPED) instrument on the Polar‐orbiting Operational Environmental Satellites (POES). Significant NO increases over the Antarctic Peninsula are likely due to precipitation of >30 keV electrons from the radiation belt slot region. NO transport is estimated using Horizontal Wind Model (HWM14) calculations. In the upper mesosphere strong eastward winds (daily mean zonal wind speed ~20–30 m s⁻¹at 80 km) during winter transport NO‐enriched air away from source regions 1–3 days following the storms. Mesospheric winds also introduce NO‐poor air into the source regions, quenching initial NO increases. Higher up, in the lower thermosphere, weaker eastward winds (~5–10 m s⁻¹at 100 km) are less effective at redistributing NO zonally.

Lightning discharges are known to inject whistler waves into the inner magnetosphere over a wide region around their source. When a discharge occurs, it radiates electromagnetic energy into the Earth‐ionosphere waveguide, some of which couples into the whistler mode and propagates through the ionospheric plasma away from the Earth. Previous studies have discussed the effects of whistler‐induced electron precipitation and radiation belt losses associated with lightning. However, to date, there has been no research on the long‐term effects of this accumulated impact. Here, we use data from the World Wide Lightning Location Network, which has continuously monitored global lightning activity since 2004, to obtain 1 year of lightning data and categorized them into L‐shell ranges, hemispheres, and magnetic local times. We then use Van Allen Probe's Energetic Particle, Composition, and Thermal Plasma Suite from both satellites (RBSP‐A/B) to measure particle fluxes in the inner belts under the same criteria. We compare these two quantities by calculating the correlation coefficients between selected electron energy channels, including pitch angle distribution, and lightning activity under different conditions. Although we found a weak to moderate relationship between lightning activity and electron flux perturbations, the correlation was not as strong as expected from theoretical predictions. Variations in electron fluxes related to substorm activity were of the same order of magnitude as that from lightning activity, even at low L shells.

Many factors influence relativistic outer radiation belt electron fluxes, such as waves in the ultralow frequency (ULF) Pc5, very low frequency (VLF), and electromagnetic ion cyclotron (EMIC) frequency bands, seed electron flux, Dst disturbance levels, substorm occurrence, and solar wind inputs. In this work we compared relativistic electron flux poststorm versus prestorm using three methods of analysis: (1) multiple regression to predict flux values following storms, (2) multiple regression to predict the size and direction of the change in electron flux, and (3) multiple logistic regression to predict only the probability of the flux rising or falling. We determined which is the most predictive model and which factors are most influential. We found that a linear regression predicting the difference in prestorm and poststorm flux (Model 2) results in the highest validation correlations. The logistic regression used in Model 3 had slightly weaker predictive abilities than the other two models but had the most value in providing a prediction of the probability of the electron flux increasing after a storm. Of the variables used (ULF Pc5 and VLF, seed electrons, substorm activity, and EMIC waves), the most influential in the final model were ULF Pc5 waves and the seed electrons. IMF Bz, Dst, and solar wind number density, velocity, and pressure did not improve any of the models, and were deemed unnecessary for effective predictions.

The atmospheric effects of precipitating electrons are not fully understood, and uncertainties are large for electrons with energies greater than ~30 keV. These electrons are underrepresented in modeling studies today, primarily because valid measurements of their precipitating spectral energy fluxes are lacking. This paper compares simulations from the Whole Atmosphere Community Climate Model (WACCM) that incorporated two different estimates of precipitating electron fluxes for electrons with energies greater than 30 keV. The estimates are both based on data from the Polar Orbiting Environmental Satellite Medium Energy Proton and Electron Detector (MEPED) instruments but differ in several significant ways. Most importantly, only one of the estimates includes both the 0° and 90° telescopes from the MEPED instrument. Comparisons are presented between the WACCM results and satellite observations poleward of 30°S during the austral winter of 2003, a period of significant energetic electron precipitation. Both of the model simulations forced with precipitating electrons with energies >30 keV match the observed descent of reactive odd nitrogen better than a baseline simulation that included auroral electrons, but no higher energy electrons. However, the simulation that included both telescopes shows substantially better agreement with observations, particularly at midlatitudes. The results indicate that including energies >30 keV and the full range of pitch angles to calculate precipitating electron fluxes is necessary for improving simulations of the atmospheric effects of energetic electron precipitation.

Electromagnetic ion cyclotron (EMIC) waves have long been considered to be a significant loss mechanism for relativistic electrons. This has most often been attributed to resonant interactions with the highest amplitude waves. But recent observations have suggested that the dominant energy of electrons precipitated to the atmosphere may often be relatively low, less than 1 MeV, whereas the minimum resonant energy of the highest amplitude waves is often greater than 2 MeV. Here we use relativistic electron test particle simulations in the wavefields of a hybrid code simulation of EMIC waves in dipole geometry in order to show that significant pitch angle scattering can occur due to interaction with low‐amplitude short‐wavelength EMIC waves. In the case we examined, these waves are in the H band (at frequencies above the He⁺gyrofrequency), even though the highest amplitude waves were in the He band frequency range (below the He⁺gyrofrequency). We also present wave power distributions for 29 EMIC simulations in straight magnetic field line geometry that show that the high wave number portion of the spectrum is in every case mostly due to the H band waves. Though He band waves are often associated with relativistic electron precipitation, it is possible that the He band waves do not directly scatter the sub‐megaelectron volts (sub‐MeV) electrons, but that the presence of He band waves is associated with high plasma density which lowers the minimum resonant energy so that these electrons can more easily resonate with the H band waves.