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During the 17 March 2015 geomagnetic storm, citizen scientist observations from Dunedin (45.95°S, 170.32°E), New Zealand, revealed a bright wide red arc known as stable auroral red (SAR) arc evolving into a thin white‐mauve arc, known as Strong Thermal Emission Velocity Enhancement (STEVE). An all‐sky imager at the Mount John Observatory (43.99°S, 170.46°E), 200 km north of Dunedin, detected an extremely bright arc in 630.0 nm, with a peak of ∼6 kR, colocated with the arc measured at Dunedin at an assumed height of 425 km. Swarm satellite data measured plasma parameters that showed strong subauroral ion drift signatures when the SAR arc was observed. These conditions intensified to extremely high values in a thinner channel when STEVE was present. Our results highlight the fast evolution of plasma properties and their effects on optical emissions. Current theories and models are unable to reproduce or explain these observations.

We utilized citizen scientist photographs of subauroral emissions in the upper atmosphere and identified a repeatable sequence of proton aurora and subauroral red (SAR) arc during substorms. The sequence started with a pair of green diffuse emissions and a red arc that drifted equatorward during the substorm expansion phase. Simultaneous spectrograph and satellite observations showed that they were subauroral proton aurora, where ion precipitation created secondary electrons that illuminated aurora in green and red colors. The ray structures in the red arc also indicated existence of low‐energy electron precipitation. The green diffuse aurora then decayed but the red arc (SAR arc) continued to move equatorward during the substorm recovery phase. This sequence suggests that the SAR arc was first generated by secondary electrons associated with ion precipitation and may then transition to heat flux or Joule heating. Proton aurora provides observational evidence that ion injection to the inner magnetosphere is the energy source for the initiation of the SAR arc.

While low and high‐latitude ionospheric scintillation have been extensively reported, significantly less information is available about the properties of and conditions leading to mid‐latitude scintillations. Here, we report and discuss scintillation observations made in the Southern United States (UT Dallas, 32.99°N, 96.76°W, 43.2°N dip latitude) on June 1st, 2013. The measurements were made by a specialized dual‐frequency GPS‐based scintillation monitor which allowed us to determine main properties of this mid‐latitude scintillation event. Additionally, simultaneous airglow observations and ionospheric total electron content (TEC) maps provided insight on the conditions leading to observed scintillations. Moderate amplitude scintillations (S₄>∼0.4) occurred in both L1 and L2C signals, and severe (S₄ > ∼0.8) events occurred in L2C signals at low (<30°) elevation angles. Phase scintillation accompanied amplitude fadings, with maximum σ_ϕvalues exceeding 0.5 radians in L2C. We also show that the observed phase scintillation magnitudes increased with amplitude scintillation severity. Decorrelation times were mostly between 0.25 and 1.25 s, with mean value around 0.65 s for both L1 and L2C. Frequency scaling of S₄matched fairly well the predictions of weak scattering theory but held for observations of moderate and strong amplitude scintillation as well. Scintillation occurred during the main phase of a modest magnetic storm that, nevertheless, prompted an extreme equatorward movement of the mid‐latitude trough and large background TEC enhancements over the US. Scintillations, however, occurred within TEC and airglow depletions observed over Texas. Finally, scintillation properties including severity and rapidity, and associated TEC signatures are comparable to those associated with equatorial spread F.

An all‐sky imager at El Leoncito Observatory (−31.8°, 69.3°W, 18.2° magnetic latitude) is used to study 630.0‐nm airglow emissions related to medium‐scale traveling ionospheric disturbances (MSTIDs). On the night of 6 December 2007 an unusual event consisting of bright bands propagating northwestward was observed. Enhancements in total electron content from ground‐based Global Positioning System receivers were observed collocated with the bright airglow bands. A regional Global Positioning System‐derived total electron content map matches the direction of motion, scale size, and location of these bright bands. Model results includingFregion coupling withEregion structures reproduce the characteristics of the bright bands. Specific conditions in theEregion must exist in order to observe these unusual MSTIDs consisting of propagating bright bands only.