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Pulsating aurora, which consists of diffuse patches blinking on and off, is caused by pitch angle scattering of radiation belt electrons into the loss cone by lower-band chorus waves. Understanding the drivers of pulsating aurora is important as it is a long-lasting and widespread phenomenon, accounting for significant energy transfer from the solar wind into the ionosphere. Substorm injections, which transport electrons from the magnetotail into the inner magnetosphere, are one source of electrons in this region. Injections have been observed simultaneously with pulsating aurora during conjunctions between ground cameras and satellites. In addition, previous work has also shown that substorms can enhance chorus activity (the fundamental process that produces pulsating aurora), providing a mechanism linking substorms to pulsating aurora. To further study this connection, we used the Van Allen Probes and all-sky cameras to look at events where pulsating aurora and substorm injections were observed at different locations in Magnetic Local Time (MLT), rather than focusing only on conjunctions. To make this comparison, we calculated the drift rate of electrons originating from observed injections and projected their motion forward in time until their Magnetic Local Time was the same as the ground camera. When the electrons are located at the same MLT as the ground camera, the pulsating aurora they cause would most likely occur in the field of view of the camera. We compared the time drifting substorm-injected particles arrived at the MLT of the camera to when pulsating aurora was observed. We found several instances where the initiation or intensification of pulsating aurora was accompanied by the arrival of substorm-injected electrons. This observation gives further evidence that pulsating aurora can be enhanced by or occur after substorm injections.

In this paper we describe K2, a comprehensive simulation model of Earth’s radiation belts that includes a wide range of relevant physical processes. Global MHD simulations are combined with guiding-center test-particle methods to model interactions with ultra low-frequency (ULF) waves, substorm injections, convective transport, drift-shell splitting, drift-orbit bifurcations, and magnetopause shadowing, all in self-consistent MHD fields. Simulation of local acceleration and pitch-angle scattering due to cyclotron-scale interactions is incorporated by including stochastic differential equation (SDE) methods in the MHD-particle framework. The SDEs are driven by event-specific bounce-averaged energy and pitch-angle diffusion coefficients. We present simulations of electron phase-space densities during a simplified particle acceleration event based on the 17 March 2013 event observed by the Van Allen Probes, with a focus on demonstrating the capabilities of the K2 model. The relative wave-particle effects of global scale ULF waves and very-low frequency (VLF) whistler-mode chorus waves are compared, and we show that the primary acceleration appears to be from the latter. We also show that the enhancement with both ULF and VLF processes included exceeds that of VLF waves alone, indicating a synergistic combination of energization and transport processes may be important.

Pulsating aurora are common diffuse-like aurora. Studies have suggested that they contain higher energy particles than other types and are possibly linked to substorm activity. There has yet to be a quantitative statistical study of the variation in pulsating aurora energy content related to substorms. We analyzed the inverted energy content from 53 events using the Poker Flat Incoherent Scatter Radar. To reduce the uncertainty, we split the differential energy flux into low and high energy using the limit of 30 keV. We also analyzed the lower altitude boundary of the electron density profile, characterized by a number density of >1010 m−3, and used this as a proxy for high energy. We compared both of these to magnetic local time (MLT), AE index, and temporal proximity to substorm onset. There was a slight trend in MLT, but a much stronger one in relation to both substorm onset and AE index. For higher AE and closer to onset the total energy flux and flux above 30 keV increased. In addition, this higher energy remained enhanced for an hour after substorm onset. Our results confirm the high energy nature of pulsating aurora, demonstrate the connection to substorms, and imply their importance to coupling between the magnetosphere and atmosphere.

It is well established that, in order to perform at their peak ability, a person must feel accepted, safe, and valued at work. Therefore, it is imperative to bring Diversity, Equity, and Inclusion (DEI) efforts to the forefront of Heliophysics over the next decade and well beyond. This position paper outlines three specific recommendations to make the Heliophysics community more diverse, equitable, and inclusive by improving the accessibility and accountability. These recommendations are: performing consistent collection and analysis of demographic data across different agencies, reimagining undergraduate Heliophysics internships using the SOARS® model, and providing conference funding for DEI speakers whose expertise lies outside the field of Heliophysics. These targeted recommendations have a well-documented positive impact, are simple to implement, and follow other scientific communities’ recent recommendations for making the science, technology, engineering, and mathematics fields more diverse, equitable, and inclusive.

We present a Python implementation of a D- and E-region chemistry and ionization code called pyGPI5. Particle precipitation that penetrates into the E- and D-region of the ionosphere-thermosphere causes significant enhancements of the electron density. Dissociative recombination of molecular ions with electrons is the primary electron loss mechanism in the E-region, down to approximately 85 km. However, below 85 km, chemical processes become significantly more complicated with positive and negative ions being generated in addition to electrons. The complex D-region ion chemistry has been known for many decades. We present a formulation to quantify the concentrations of four ion species composed of positive and negative, light and heavy ions, and the electrons. The implementation we describe in this investigation solves five ordinary stiff differential equations simultaneously. We present an overview of the code, along with discussions of the reaction rates, and assumptions used in the model. We describe an implementation of the electron transport model to quantify the altitude ionization profile caused by energetic particle precipitation. We show how to instantiate the model, generate the ion and electron profiles as a function of altitude for background conditions, how to generate altitude ionization profiles, and running the code to produce ion and electron profiles caused by energetic particle precipitation. Recent investigations that have used a D-region chemistry model are discussed, along with some applications.

Efforts to model and predict energetic electron fluxes in the radiation belts are highly sensitive to local wave-particle interactions. In this study, we use multi-point measurements of precipitating and trapped electron fluxes to investigate the dynamic variation of chorus wave-particle interactions during the 17 March 2013 storm. Quasilinear theory characterizes the chorus wave-particle interaction as a diffusive process, with the diffusion coefficients depending on the particle energy and pitch angle, as well as the background plasma parameters such as the wave intensity and plasma density. These plasma parameters in the radiation belts are spatially localized and time-varying, so we construct event-specific diffusion coefficients using MEPED (onboard POES/MetOp) measurements of electron fluxes at low Earth orbit. This new method provides realistic diffusion coefficients for chorus waves that account for changes in the wave intensity, the plasma density, and the magnetic field strength in the outer radiation belt. We show that the inferred chorus intensity is significantly lower than previous estimates that use MEPED observations since the same amount of increased precipitation by 30–300 keV electrons can be explained by a change in the plasma density. This technique therefore allows for us to create time varying, global maps of the plasma-gyrofrequency ratio (fpe/fce), and therefore plasma density, in the outer radiation belts using the MEPED measurements. The global density estimates compare reasonably well to in situ density measurements from RBSP-B.

The Space Physics and Aeronomy (SPA) Section of the American Geophysical Union (AGU) created a Nomination Task Force (NTF) in 2017 upon concerns that the numbers of women nominated for AGU Fellow were significantly lower than would be expected based on SPA membership representation, including as low as zero in two of the four preceding years. Now that the NTF has been in existence through four cycles of AGU Honors and Awards, the outcomes indicate the success of the NTF in increasing the number of nominations for scientists from historically marginalized groups. These data indicate that the work of the NTF has enhanced the nomination pool rather than occurring at the expense of other nominees. Until recently, the ability to collect and distribute demographic information has been limited, and cisgender binary identities are often inferred. Moving forward it is a goal of AGU to be more inclusive and intentional with respect to gender, racial, and ethnic identities. We share our best practices and success stories with a broad audience to help others build upon the work of the NTF within their own institutions and professional groups. We also discuss challenges that we are still facing and provide suggestions for continuing to improve the process.

Many spacecraft fly within or through a natural and variable particle accelerator powered by the coupling between the magnetosphere and the solar wind: the Earth’s radiation belts. Determining the dominant pathways to plasma energization is a central challenge for radiation belt science and space weather alike. Inward radial transport from an external source was originally thought to be the most important acceleration process occurring in the radiation belts. Yet, when modeling relied on a radial diffusion equation including electron lifetimes, notable discrepancies in model-observation comparisons highlighted a need for improvement. Works by Professor Richard M. Thorne and others showed that energetic (hundreds of keV) electrons interacting with whistler-mode chorus waves could be efficiently accelerated to very high energies. The same principles were soon transposed to understand radiation belt dynamics at Jupiter and Saturn. These results led to a paradigm shift in our understanding of radiation belt acceleration, supported by observations of a growing peak in the radial profile of the phase space density for the most energetic electrons of the Earth’s outer belt. Yet, quantifying the importance of local acceleration at the gyroscale, versus large-scale acceleration associated with radial transport, remains controversial due to various sources of uncertainty. The objective of this review is to provide context to understand the variety of challenges associated with differentiating between the two main radiation belt acceleration processes: radial transport and local acceleration. Challenges range from electron flux measurement analysis to radiation belt modeling based on a three-dimensional Fokker-Planck equation. We also provide recommendations to inform future research on radiation belt radial transport and local acceleration.

Abstract On 28 July 2021, within the Geospace Environment Modeling Virtual Summer Workshop, a joint panel discussion organized by the “System Understanding of Radiation Belt Particle Dynamics through Multi‐spacecraft and Ground‐based Observations and Modeling” and “ULF wave Modeling, Effects, and Applications” focus groups was held. The panelists, organizers, and the audience discussed the nature and unresolved questions of radiation belt electron flux enhancements. In this commentary we provide the outcomes of this discussion.