Transport, scattering, and loss of keV electrons are one of the largest unresolved issues of geospace physics. This ISSI team would address two connected and compelling scientific objectives:
- What is the state of the art regarding keV electron dynamics and physics in the near-Earth plasma sheet and auroral zone?
- What are the highest priority steps needed for substantial advancement on understanding keV electron fluxes in geospace?
It is important to convene this ISSI team now because of a rapid expansion of this field in recent years. Thanks to the successful operation of several missions (e.g., THEMIS, Cluster, Van Allen Probes, MMS, Arase, geosynchronous satellites from NOAA and LANL, Reimei, DMSP, NOAA-POES, to name a few), there is now a substantial data set for keV electrons in geospace. These missions are not new but they have accumulated a large amount of data with most operating for over a solar cycle. This is a particular great time to analyze Cluster energetic electron observations as a whole, since these measurements are now finished after more than 20 years of operations. These large data sets have allowed for the creation of new empirical and machine-learning-based models of keV electrons in the plasma sheet that take into account the full range of solar wind driving parameters and geomagnetic activity levels. While we have gained new understanding, these new tools still cannot predict the rapid changes during injection events. Now is an excellent time to finally conduct an extensive joint review on them, to gather the relevant experts together to debate and discuss why our approaches thus far have not yielded accurate predictions of the rapid flux increases. In addition, there are several upcoming missions of keen interest for this ISSI team, in particular the SMILE concept – the Solar wind Magnetosphere Ionosphere Link Explorer – a joint project of the European Space Agency and the Chinese Academy of Sciences. It is in development now and expected to launch in May 2025. The work of this team would greatly inform the interpretation of the initial results from that mission. Another potential future mission of relevance for this team is the MAAX concept – the Magnetospheric Auroral Asymmetry eXplorer – currently in competitive Phase A study in the NASA Heliophysics Small Explorer Program. It would have two identical ultraviolet imagers to view the full auroral oval in both hemispheres simultaneously, revealing the flow of energy through geospace as evidenced in these precipitating particles. Therefore, it is timely to assess what we have learned and where we need to go. ISSI provides the opportunity to bring together topical experts to concentrate efforts on ideating the advancements needed in this field.
This team would synthesize the current state of knowledge on keV electrons in geospace by conducting a robust review of the topic. Based on the synthesis of this review, we would brainstorm ideas of the new analysis, models, theories, or measurements necessary to make significant progress. We would then categorize these according to an expected timeline for the community to make progress on that item, as well the impact it would have on the state of the field. From this matrix of possible paths forward, the team would choose one and begin work on it. The result would be a compilation of what is known now, the distillation of what is needed for substantial new progress, and research towards an impactful first step towards these goals.