A rare aurora appeared briefly over southern Brazil on Jan. 19 during a powerful geomagnetic storm. Luckily for us, one photographer was at the right place at the right time to capture the fleeting scene.
Astrophotographer Egon Filter captured the faint purple-red glow from Cambará do Sul, in Brazil's Rio Grande do Sul state, during the peak of the geomagnetic storm. Auroras are typically confined to high latitudes near Earth's north and south magnetic poles, making sightings in the Southern Hemisphere this far north of Antarctica very rare.
Filter had always dreamt of photographing the aurora australis (southern lights) in Brazil, but Rio Grande do Sul state is located between the 27 and 33 degrees south latitude, far outside the usual auroral zone.
"For an aurora to be visible at low latitudes, a very violent and exceptional solar storm is necessary," Filter told Space.com in an email.
To Filter's delight, that condition was met on Jan. 19, when a strong geomagnetic storm struck Earth. He was watching the southern sky when the glow appeared.
"It was a fantastic, truly thrilling feeling to check the camera and see that I had captured the image," Filter continued. "I took a few more pictures and, after a few minutes, it had already disappeared."
How did auroras reach Brazil?
The short-lived display occurred inside the South Atlantic Anomaly, a region where Earth's magnetic field is weaker than elsewhere, according to spaceweather.com. This region is usually associated with suppressed auroral activity, not enhanced displays, and one leading explanation is that the weak and disorganized magnetic fields in the anomaly do a poor job of focusing and accelerating solar wind particles. As a result, any auroras that do form tend to appear as faint, diffuse glows rather than bright, well-defined curtains.
Spaceweather.com noted that the glow could also potentially have been a stable auroral red (SAR) arc, a diffuse band that can appear during strong geomagnetic storms when energy from Earth's ring current leaks into the upper atmosphere. SAR arcs have been observed at lower latitudes during strong storms and are typically quite faint.
However, solar physicist Tamitha Skov says the geometry of the Brazilian observation points more strongly to aurora than a SAR arc. "What makes this particular observation more remarkable is that it is observed high in the sky over Brazil and not near the southern horizon," Skov told Space.com. Given Brazil's low latitude, Skov explained that the glow was most likely diffuse equatorial aurora penetrating through the South Atlantic Anomaly, rather than a SAR arc, which is more commonly found hugging the horizon.
"It is aurora, but it is diffuse (not discrete) and it comes from a different source than we typically associate with the auroral zone," Skov explained.
While the sight is rare, Skov emphasized that it was not unexpected. She explained that the sun is currently returning to a more "active posture" and that recent solar activity is closer to what scientists consider normal when averaged over the past 24 solar cycles.
"These observations are consistent with the expected behavior from the Sun-Earth system, right now," Skov said. "Many of us have been predicting we would see this kind of aurora for years now. In fact, some of us have actively asked aurora field reporters to be on the lookout for it."
Editor's Note: If you snap a photo of the northern or southern lights or any other sky phenomena and would like to share it with Space.com's readers, send your photo(s), comments, and your name and location to spacephotos@space.com.
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