Tone and Charles Deehr in Fairbanks, October 2021. Both photos courtesy Charles Deehr. 3. (Courtesy Photo / Charles Deehr)

Alaska Science Forum: Red aurora rare enough to be special

In decades of sky-watching in the north, he has seen a few red auroras, but not many.

By Ned Rozell

Charles Deehr will never forget his first red aurora. On Feb. 11, 1958, Deehr was a student at Reed College in Portland, Oregon. He asked a Fulbright student from Norway named Tone to the Portland Symphony that night.

They went for a stroll on a golf course after the concert. Looking past the treetops, they noticed the sky was blood red.

People as far south as Mexico saw the red sky that night. Some thought Martians. Others thought Christ was visiting for the second time. In Portland, people thought a forest fire was causing the glow.

Deehr knew better, because he was studying the physics of Earth and space. Under the crimson sky, he was sure of two things: he and Tone were seeing a great red aurora, and he would ask her on another date.

A rare red aurora over Alaska in February 1958. (Courtesy Photo / Geophysical Institute)

A rare red aurora over Alaska in February 1958. (Courtesy Photo / Geophysical Institute)

The Deehrs have now been married 61 years. Charles — Chuck to his friends — was a space-physicist and aurora forecaster at the University of Alaska Fairbanks for most of that time. In decades of sky-watching in the north, he has seen a few red auroras, but not many.

Fringes of red and blue hanging from aurora curtains — the result of particles from the sun reacting with nitrogen in the upper atmosphere — happen often, but the great displays that flood the sky with diffuse red light are rare.

Red aurora displays happen so high in the sky they are often the only form of aurora ever seen by people in the mid-latitudes.

In A.D. 37, a great red aurora showed itself to the citizens of Rome. Those in London gazed up at a red sky in September 1839. A blazing display in 1938 lit the sands of the Sahara Desert in northern Africa. Deehr and his date witnessed one of the most spectacular displays in 1958. Others have happened in 1989, 2000 and 2001.

Great red auroras are rare because they require a perfect mix of heavenly conditions.

“To get a pure red aurora, you need two things from the sun,” Deehr said. “Lots of solar flares with ultraviolet radiation to heat the Earth’s atmosphere, and lots of coronal mass ejections to power the Earth’s magnetospheric generator of aurora.”

Charles and Tone Deehr with their daughter Tina near Dawson City, Yukon in 1961. (Courtesy Photo / Charles Deehr)

Charles and Tone Deehr with their daughter Tina near Dawson City, Yukon in 1961. (Courtesy Photo / Charles Deehr)

The green aurora northerners enjoy almost every dark night is a product of particles cast off by the sun that stream outward into space. This solar wind takes a day to two to reach Earth. It flows over the planet and reacts with Earth’s magnetic field. In the upper atmosphere, this electrical discharge reacts with gases, causing them to glow in the same way electricity fires up a neon light.

Green auroras occur at about 60 miles above Earth. Pure red auroras are much higher, from about 200 to 300 miles up, which allows people closer to the equator to see them. An important gas remaining at that altitude is oxygen, and electrons that excite the oxygen atoms there produce a red light as pure as a laser.

Cameras and phones that can capture more light wavelengths than our eyes sometimes show red in aurora photos in which the photographer only saw greens. Red auroras have to be 10 times as bright as green auroras for us to see that color with the naked eye.

Red auroras are unpredictable, but in the past they have tended to bunch themselves around periods when the solar cycle — an 11-year period of sun activity — features lots of solar activity.

Today, Chuck Deehr is a professor emeritus at the Geophysical Institute of the University of Alaska Fairbanks. He doesn’t expect to ever see a red aurora as brilliant as the night of Feb. 11, 1958, but some things — like a first date that leads to a 63-year partnership, four daughters, and seven grandchildren — happen only once in a lifetime.

• Since the late 1970s, the University of Alaska Fairbanks’ Geophysical Institute has provided this column free in cooperation with the UAF research community. This year is the institute’s 75th anniversary. Ned Rozell, ned.rozell@alaska.edu, is a science writer for the Geophysical Institute.

More in News

Jasmine Chavez, a crew member aboard the Quantum of the Seas cruise ship, waves to her family during a cell phone conversation after disembarking from the ship at Marine Park on May 10. (Mark Sabbatini / Juneau Empire file photo)
Ships in port for the week of July 13

Here’s what to expect this week.

A mother bear and a cub try to get into a trash can on a downtown street on July 2, 2024. Two male bears were euthanized in a different part of downtown Juneau on Wednesday because they were acting aggressively near garbage cans, according to the Alaska Department of Fish and Game. (Mark Sabbatini / Juneau Empire file photo)
Two black bears in downtown Juneau euthanized due to aggressive behavior around people

Exposed garbage, people insistent on approaching bears contribute to situation, official says

(Michael Penn / Juneau Empire file photo)
Police calls for Wedesday, July 17, 2024

This report contains public information from law enforcement and public safety agencies.

Cars arrive at Juneau International Airport on Thursday, July 11, 2024. (Mark Sabbatini / Juneau Empire file photo)
Juneau seems to have avoided major disruptions following global technology-related outage

911 centers, hospitals, airport, and public safety and emergency management agencies are operating.

People take photos of local dignitaries during the ribbon-cutting ceremony at the Teal Street Center on Thursday afternoon. (Mark Sabbatini / Juneau Empire)
Teal Street Center celebrates with ribbon-cutting a year after social agencies begin providing services

Nine organizations providing legal, disability, counseling and other help open under one roof.

Alaska Permanent Fund Corp. board chairman Ethan Schutt is seen during a special board meeting on Monday, Oct. 3, 2022, in Juneau. (James Brooks/Alaska Beacon)
Dunleavy reappoints Permanent Fund Corp. board chair Schutt after weeks of uncertainty

Gov. Mike Dunleavy has reappointed Ethan Schutt to a public seat on… Continue reading

Employees gather in front the historic Red Onion Saloon in Skagway, which will be taken over by Juneau restaurant owner Tracy LaBarge at the end of the summer tourism season. (Photo courtesy of the Red Onion Saloon)
Owner of Tracy’s King Crab Shack buys historic Red Onion Saloon in Skagway

Tracy LaBarge will take over the establishment after the 2024 summer tourism season

A memorial started on Front Street in downtown Juneau for 35-year-old Juneau resident Steven Kissack, who was experiencing homelessness, grows on Thursday with food donations and suicide hotline information. (Jasz Garrett / Juneau Empire)
As the death investigation of Steven Kissack begins, special prosecution office explains its process

Reviews can be lengthy, information limited to ensure due process, Department of Law leaders say

In this screenshot from a streamed court hearing, Attorney Thekla Hansen-Young (bottom right) speaks in front of a three-judge panel of the 9th U.S. Circuit Court of Appeals on July 18, 2024, in San Francisco. (Screenshot)
Federal appeals court appears unlikely to halt Southeast Alaska king trolling for now

A lower-court order that could stop fishing has been placed on hold since last year.

Most Read