A severe geomagnetic storm developed in Earth’s magnetosphere on January 19, producing widespread auroral emissions at latitudes far beyond the usual auroral oval. Among the most unusual observations were those made from Cambará do Sul, Brazil, located within the South Atlantic Anomaly (SAA). A diffuse purple glow appeared low in the southern sky during the peak of the storm, coinciding with planetary K-index levels above 7.
The geomagnetic storm followed the arrival of a fast coronal mass ejection (CME) launched by an X1.9 solar flare on January 18. The CME reached Earth’s magnetic field at approximately 19:20 UTC on January 19, rapidly increasing geomagnetic activity to G4 – Severe levels, according to data from the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center. The same flare event produced the strongest solar radiation storm since 2003.
During the peak of this storm, observers around the world reported intense auroral displays extending far beyond the usual polar regions. Among them was an observation noted by Dr. Tony Phillips of SpaceWeather.com, who documented a report from photographer Egon Filter in Cambará do Sul, Brazil.
The sighting described a diffuse purple band appearing within the boundaries of the South Atlantic Anomaly, a magnetic weak zone not typically associated with strong auroral activity.
The South Atlantic Anomaly is a region of reduced geomagnetic field strength centered over Brazil, where Earth’s inner Van Allen radiation belt dips unusually close to the surface.
This configuration allows a greater flux of energetic particles to penetrate the upper atmosphere. Under normal conditions, auroras are suppressed there because the local magnetic field is weak and irregular, limiting the focusing and acceleration of charged particles along magnetic field lines.
The emission recorded over Brazil was faint and diffuse, differing from the structured curtains typical of auroras at high latitudes. Its spectral and morphological characteristics suggest that the event may have been a Stable Auroral Red (SAR) arc rather than a classical aurora
SAR arcs form during intense geomagnetic storms when heat from the ring current is transferred into the ionosphere, producing red or magenta emissions at altitudes of about 400 km (250 miles). However, existing models indicate that both auroras and SAR arcs should be weaker inside the South Atlantic Anomaly, making this observation exceptional.
A comparable sighting was documented on May 10, 2024, from San Pedro de Atacama, Chile, also located beneath the South Atlantic Anomaly, where red emissions were recorded during a major geomagnetic storm. Such events offer opportunities to study how localized magnetic irregularities influence particle precipitation and energy transfer in the upper atmosphere during extreme space weather conditions.
The January 19 storm was among the strongest of Solar Cycle 25, producing auroras visible across North America, Europe, and Asia and extending to unusually low latitudes.
Continued analysis by research observatories and space weather agencies should determine whether the recorded glow represented a true aurora, a SAR arc, or a hybrid upper-atmospheric emission unique to the anomaly.