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.

Few remote sensing or in‐situ techniques can measure winds in Earth's thermosphere between altitudes of 120 and 200 km. One possible approach within this region uses Doppler spectroscopy of the optical emission from atomic oxygen at 558 nm, although historical approaches have been hindered in the auroral zone because the emission altitude varies dramatically, both across the sky and over time, as a result of changing characteristic energy of auroral precipitation. Thus, a new approach is presented that instead uses this variation as an advantage, to resolve height profiles of the horizontal wind. Emission heights are estimated using the Doppler temperature derived from the 558 nm emission. During periods when the resulting estimates span a wide enough height interval, it is possible to use low order polynomial functions of altitude to model the Doppler shifts observed across the sky and over time, and thus reconstruct height profiles of the horizontal wind components. The technique introduced here is shown to work well provided there are no strong horizontal gradients in the wind field. Conditions satisfying these caveats do occur frequently and the resulting wind profiles validate well when compared to absolute in‐situ wind measurements from a rocket‐borne chemical release. While both the optical and chemical tracer techniques agreed with each other, they did not agree with the HWM‐14 horizontal wind model. Applying this technique to wind measurements near the geomagnetic cusp footprint indicated that cusp‐region forcing did not penetrate to atmospheric heights of 240 km or lower.

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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.