At http://spaceweather.com (Tuesday 21st August 2018) … the solar wind has sparked auroral storms in the Arctic Circle. It is flowing from a wide coronal hole on the face of the Sun …
… Apparently, STEVE is not an aurora according to a new study in Geophysical Research Letters (Aug 20th). They combined satellite with ground based imagery of STEVE during a geomagnetic storm to investigate how STEVE is formed. Their conclusion it that STEVE is not an aurora.
STEVE is a purple ribbon of light that amateur astronomers in Canada have been photographing for decades. It has only recently captured the attention of scientists since 2016 – after the publication of many images of the phenomenon. It doesn't look like an aurora but appears alongside aurora during geomagnetic storms. Auroras appear when energetic particles from space rain down on Earth's atmosphere. If STEVE is an aurora then it should form in much the same way, they said. It doesn't. Steve is a distinct phenomenon that differs from aurora. It is characterised by the absence of particle precipitation – but the sky glow could be generated by a new fundamentally different mechanism in Earth's ionosphere.
Another study suggests STEVE appears most often in spring and autumn (close to the equinox). Stay tuned as we approach the 2018 autumn equinox.