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On September 28, 2017 citizen scientist observations at Alberta, Canada (51°N, 113° W) detected aurora and a thin east‐west purplish arc, known as strong thermal emission velocity enhancement (STEVE) that lasted less than 20 min. All‐sky imagers at subauroral latitudes measured stable auroral red (SAR) arcs during the entire night. The imager at Bridger, MT (45.3°N, 108.9°W) also measured a STEVE. The overlapping geometry allowed to determine that the height of STEVE was 225–275 km. STEVE is brighter in the 630.0 nm images in the West and almost merges with the SAR arc in the East. A DMSP satellite pass in the southern hemisphere was at the conjugate location of the Bridger imager during the STEVE observation. When mapped into the northern hemisphere intense subauroral ion drift and subauroral polarization streams were detected associated with the two optical signatures measured in 630.0 nm.

 

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.

 

Abstract. An intriguing and rare gravity wave event was recorded on the night of 25 April 2017 using a multiwavelength all-sky airglow imager over northernGermany. The airglow imaging observations at multiple altitudes in themesosphere and lower thermosphere region reveal that a prominent upward-propagating wave structure appeared in O(1S) and O2 airglowimages. However, the same wave structure was observed to be very faint in OH airglow images, despite OH being usually one of the brightest airglowemissions. In order to investigate this rare phenomenon, the altitudeprofile of the vertical wavenumber was derived based on colocated meteorradar wind-field and SABER temperature profiles close to the event location.The results indicate the presence of a thermal duct layer in the altituderange of 85–91 km in the southwest region of Kühlungsborn, Germany.Utilizing these instrumental data sets, we present evidence to show how aleaky duct layer partially inhibited the wave progression in the OH airglowemission layer. The coincidental appearance of this duct layer is responsible for the observed faint wave front in the OH airglow images compared O(1S) and O2 airglow images during the course of the night over northern Germany.