Aug. 20, 2018: A new type of aurora nicknamed “STEVE” may not be an aurora at all, according to a new paper published August 20th in the Geophysical Research Letters. A group of researchers combined satellite data with ground-based imagery of STEVE during a geomagnetic storm to investigate how STEVE is formed. “Our main conclusion is that STEVE is not an aurora,” said Bea Gallardo-Lacourt, a space physicist at the University of Calgary in Canada and lead author of the new study.

STEVE is a purple ribbon of light that amateur astronomers in Canada have been photographing for decades, belatedly catching the attention of the scientific community in 2016. It doesn’t look exactly like an aurora, but it often appears alongside auroras during geomagnetic storms. Is it an aurora — or not? That’s what Gallardo-Lacourt’s team wanted to find out.

Auroras appear when energetic particles from space rain down on Earth’s atmosphere during geomagnetic storms. If STEVE is an aurora, they reasoned, it should form in much the same way. On March 28, 2008, STEVE appeared over eastern Canada just as NOAA’s Polar Orbiting Environmental Satellite 17 (POES-17) passed overhead. The satellite, which can measure the rain of charged particles that causes auroras, went directly above the purple ribbon. Gallardo-Lacourt’s team looked carefully at the old data and found … no rain at all.

“Our results verify that this STEVE event is clearly distinct from the aurora borealis since it is characterized by the absence of particle precipitation,” say the researchers. “Interestingly, its skyglow could be generated by a new and fundamentally different mechanism in Earth’s ionosphere.”

Another study has shown that STEVE appears most often in spring and fall. With the next equinox only a month away, new opportunities to study STEVE are just around the corner. Stay tuned and, meanwhile, read the original research here.

Realtime STEVE Photo Gallery

August 15, 2018: This summer, something strange has been happening in the mesosphere. The mesosphere is a layer of Earth’s atmosphere so high that it almost touches space. In the rarefied air 83 km above Earth’s surface, summertime wisps of water vapor wrap themselves around speck of meteor smoke. The resulting swarms of ice crystals form noctilucent clouds (NLCs), which can be seen glowing in the night sky at high latitudes.

And, no, that’s not the strange thing.

Northern sky watchers have grown accustomed to seeing these clouds every summer in recent years. They form in May, intensify in June, and ultimately fade in July and August. This year, however, something different happened. Instead of fading in late July, the clouds exploded with unusual luminosity. Kairo Kiitsak observed this outburst on July 26th from Simuna, Estonia:

“It was a mind-blowing display,” says Kiitsak. “The clouds were visible for much of the night, with intense ripples for 3 hours.”

Other observers saw similar displays in July and then, in August, the clouds persisted. During the first half of August 2018, reports of NLCs to Spaceweather.com have tripled compared to the same period in 2017. The clouds refuse to go away.

Researchers at the University of Colorado may have figured out why. “There has been an unexpected surge of water vapor in the mesosphere,” says Lynn Harvey of  Colorado’s Laboratory for Atmospheric and Space Physics (LASP).  This plot, which Harvey prepared using data from NASA’s satellite-based Microwave Limb Sounder (MLS) instrument, shows that the days of late July and August 2018 have been the wettest in the mesosphere for the past 11 years:

“July went out like a lion!” says Harvey.

In addition to being extra wet, the mesosphere has also been a bit colder than usual, according to MLS data. The combination of wet and cold has created favorable conditions for icy noctilucent clouds.

Harvey and her colleagues are still working to understand how the extra water got up there. One possibility involves planetary wave activity in the southern hemisphere which can, ironically, boost the upwelling of water vapor tens of thousands of miles away in the north. The phenomenon could also be linked to solar minimum, now underway. It is notable that the coldest and wettest years in the mesosphere prior to 2018 were 2008-2009–the previous minimum of the 11-year solar cycle.

Stay tuned for updates and, meanwhile, be alert for NLCs.

Realtime Noctilucent Cloud Photo Gallery