First Observation of Temporal Variation of STEVE Altitudes Using Triangulation by Two Color Cameras

We present a unique triangulation measurement of Strong Thermal Emission Velocity Enhancement (STEVE) observed on Sept 3rd, 2022, at Athabasca, Canada. Using two Digital single-lens reflex (DSLR) color cameras with all-sky fish-eye lenses, we show the profile of STEVE altitude variation over time in 1 min resolution for the first time. We estimate the altitude variation of its visible purplish arc and green picket fence structures. We also compare the DLSR camera images with narrowband all-sky images of an Optical Mesosphere Thermosphere Imager (OMTI) to see the correspondence of color camera images with 630 nm and OH-band auroral/airglow emission images. The height of the purplish STEVE arc was stable at 150–170 km while present (∼0,546–0,633 UT), except for a short excursion to ∼200 km at 0,600 UT. The green picket fence structures appeared at 0,549 UT when the intensity of the STEVE arc started to intensify. They presented only for ∼7 min, and their altitude was steady at ∼110 km. The vertical movement of the STEVE arc to ∼200 km was found to be accompanied by the motion across the local magnetic field lines, suggesting a southward E × B drift underlying the westward ion drift. From the comparison with the OMTI images, we find that the purplish STEVE arc moved closer to the 630 nm arc in the all-sky image when it rose to a higher altitude, indicating the occurrence of electron heating at a same or slightly higher altitude than the STEVE.