Few studies have yet explicitly connected observed auroral forms to satellite measurements of the precipitating particles and fields. In particular, Liang et al.  have now distinguished the red line and green line aurora, which is new and noteworthy. This identification provides direct evidence that the lower-energy electrons associated with broadband (or Alfvenic) acceleration preferentially produce red-line emission.
With these joint optical and e-POP (Enhanced-Polar-Outflow-Probe) particle observations of Alfvenic auroras, the authors show that the 630 nm red-line auroras evolve distinctly from those seen on other optical instruments and are associated with low-energy precipitation bursts. These precipitation bursts are often the result of suprathermal electron bursts, which are characterized by a broad energy spectrum and a field-aligned pitch angle distribution.
Citation: Liang, J., Shen, Y., Knudsen, D., Spanswick, E., Burchill, J., & Donovan, E. . e‐POP and red line optical observations of Alfvénic auroras. Journal of Geophysical Research: Space Physics, 124. https://doi.org/10.1029/2019JA026679
—Viviane Pierrard, Editor, JGR: Space Physics