On January 19, a remarkable celestial event unfolded over the skies of southern Brazil, as a powerful geomagnetic storm pushed the boundaries of auroral activity to unprecedented latitudes. A photographer's patience and preparedness paid off when he captured a fleeting glimpse of the southern lights—a phenomenon rarely seen so far north of its usual polar domain.
The stunning image was captured by Brazilian astrophotographer Egon Filter from Cambará do Sul, located in Rio Grande do Sul state. This region sits between 27 and 33 degrees south latitude, placing it far outside the typical auroral zone that normally hugs the Antarctic continent. For observers at such relatively low latitudes to witness this spectacle, an exceptionally violent solar event is required—precisely what occurred on that January day.
Auroras, known as the aurora borealis in the Northern Hemisphere and aurora australis in the Southern Hemisphere, are natural light displays caused by charged particles from the sun interacting with Earth's magnetic field and atmosphere. Typically confined to high-latitude regions near the magnetic poles, these dancing curtains of light are a common sight for those living in places like Alaska, northern Canada, Scandinavia, or the southernmost reaches of New Zealand and Argentina. However, sightings in Brazil are extraordinarily rare, making Filter's photograph a significant documentation of an unusual space weather event.
Filter had long harbored a dream of photographing the aurora australis from his home country. "For an aurora to be visible at low latitudes, a very violent and exceptional solar storm is necessary," he explained in correspondence with Space.com. His understanding of the stringent conditions required only heightened his excitement when the opportunity finally materialized.
The catalyst for this extraordinary display was a powerful geomagnetic storm that struck Earth on January 19. Geomagnetic storms are disturbances in Earth's magnetosphere caused by enhanced solar wind pressure and magnetic fields, often triggered by coronal mass ejections from the sun. When these storms are particularly intense, they can compress Earth's magnetic field and allow charged particles to penetrate deeper into the atmosphere than usual, creating auroras at lower latitudes.
As Filter monitored the southern sky that night, a faint purple-red glow materialized—exactly what he had been hoping for. "It was a fantastic, truly thrilling feeling to check the camera and see that I had captured the image," he recalled. The display was ephemeral, lasting only a few minutes before fading from view. Filter managed to take several photographs during this brief window, preserving a moment that few in Brazil have ever witnessed.
What makes this event even more scientifically intriguing is its occurrence within the South Atlantic Anomaly (SAA). This region, which spans from South America to southern Africa, is characterized by a weaker-than-normal magnetic field. The SAA represents a dip in Earth's protective magnetic shield, where radiation levels are higher and spacecraft often experience electronic glitches.
Paradoxically, while one might assume a weaker magnetic field would make auroral displays more common, the opposite is typically true. The disorganized magnetic fields within the anomaly are inefficient at channeling and accelerating solar wind particles into the atmosphere. Consequently, auroras that do form in this region tend to appear as faint, diffuse glows rather than the bright, structured curtains seen at higher latitudes.
Some experts have suggested that the glow captured by Filter might not be a traditional aurora at all, but rather a stable auroral red (SAR) arc. These phenomena are diffuse, reddish bands that appear during strong geomagnetic storms when energy from Earth's ring current leaks into the upper atmosphere. The ring current is a toroidal flow of charged particles that encircles Earth at altitudes of several thousand kilometers, and during intense storms, this energy can manifest as a subtle red glow at lower latitudes.
The distinction between a traditional aurora and a SAR arc is subtle but significant. While both are caused by space weather events, SAR arcs result from heating of the atmosphere by ring current energy rather than direct precipitation of particles into the atmosphere. This heating excites oxygen atoms, causing them to emit red light at a wavelength of 630 nanometers. The result is a much fainter, more uniform glow that can be difficult to distinguish from a weak aurora.
Regardless of its precise classification, Filter's photograph represents a remarkable achievement in citizen science and astrophotography. His image not only documents an extremely rare event but also provides valuable data for scientists studying the complex interactions between solar activity and Earth's magnetic environment.
The rarity of such an event cannot be overstated. Brazil's geographic location places it firmly in the tropics, far from the auroral oval that circles the Antarctic. For residents of Rio Grande do Sul, the southernmost state in Brazil, the possibility of seeing an aurora is remote even under the best of circumstances. The fact that Filter was able to not only witness but also photographically document this event speaks to both his dedication and the exceptional nature of the geomagnetic storm.
The January 19 storm was part of the sun's ongoing activity cycle, which reaches its peak approximately every 11 years. During solar maximum, the frequency and intensity of solar flares and coronal mass ejections increase, leading to more frequent and powerful geomagnetic storms. These storms can disrupt satellite communications, affect power grids, and create spectacular auroral displays. As our sun continues through its active phase, more unusual sightings may occur, though they will remain rare at tropical latitudes.
For Filter, the experience was the culmination of years of waiting and preparation. The thrill of seeing that faint glow on his camera screen represented the realization of a long-held ambition. His success serves as an inspiration to other astrophotographers and skywatchers in regions not typically associated with auroral activity, demonstrating that with patience, knowledge, and a bit of luck, extraordinary celestial events can be captured from anywhere on the planet.
The photograph also highlights the importance of understanding space weather and its effects on our planet. As we become increasingly reliant on technology vulnerable to solar activity, documenting and studying these events helps scientists improve forecasting models and prepare for potentially disruptive geomagnetic storms. Citizen scientists like Filter play a crucial role in this effort, providing ground-based observations that complement satellite data.
In the end, the fleeting purple-red glow over Cambará do Sul serves as a reminder of our planet's dynamic relationship with the sun. It demonstrates that even in regions where auroras are considered impossible, the right combination of solar activity and atmospheric conditions can create moments of unexpected beauty. For those fortunate enough to witness such events, they offer a direct, personal connection to the vast and powerful forces that shape our solar system.