Intense solar activity has been observed in recent days, highlighting the presence of a large coronal hole, covering more than 20% of the Sun’s surface, capable of significantly accelerating the solar wind. During the same period, two M-class solar flares and one X-class flare were recorded, causing an abrupt increase in electromagnetic radiation emitted at higher-energy wavelengths.
On January 19, the CACTus software identified two halo-type coronal mass ejections (CMEs), characterized by a wide angular extent and high potential for impact on Earth’s space environment. These ejections were associated with an X1.9-class solar flare that occurred on January 18, which launched an extremely fast CME into space, with speeds exceeding 1400 km/s. After about two days of propagation through the interplanetary medium, a transit time considered short, the ejection directly impacted Earth’s magnetosphere.
Measurements from the DSCOVR satellite, positioned at the Lagrange point L1, indicated intense disturbances in the solar wind and the interplanetary magnetic field. The Bz component showed abrupt variations and high values, on the order of tens of nanoteslas, typical of highly geoeffective events. As a result, the magnetosphere underwent strong compression, with the magnetopause being displaced to distances less than eight Earth radii, creating favorable conditions for an efficient transfer of energy from the solar wind to the magnetospheric system.
Satellites from the GOES series recorded remarkable responses in the Van Allen Radiation Belts, including a rapid dropout of relativistic electrons in the outer belt, as well as an extreme solar energetic particle event, with high fluxes of high-energy protons. The flux of electrons with energies equal to or greater than 2 MeV showed a reduction of more than three orders of magnitude in approximately three hours, associated with the arrival of the interplanetary coronal mass ejection (ICME). This decrease in the number of trapped electrons resulted in intense particle precipitation over the auroral regions and over the South American Magnetic Anomaly, affecting the atmospheric composition of these areas.
The geomagnetic storm peaked on the night of January 19, being classified as severe (G4). The Kp index ranged between 8+ and 9-, while magnetometers from the EMBRACE/INPE Program recorded significant disturbances in the geomagnetic field. The Dst index initially reached -119 nT and continued to intensify throughout the 20th, reaching -218 nT at the time of writing. In the auroral region, the AE index exceeded 1000 nT, with peaks close to 4000 nT, indicating intense activity of the auroral currents.
In the ionosphere, an expansion of particle precipitation was observed in the region of the South American Magnetic Anomaly, allowing the occurrence of auroral behaviors in equatorial latitudes. In the center of the anomaly, data obtained in Cachoeira Paulista indicated a significant increase in ionization, evidenced by the behavior of echoes from the upper ionospheric regions. In addition, plasma bubbles, normally frequent at this time of year, were suppressed during the night of January 19-20.
The combination of high speeds, intense magnetic fields, and short arrival time gives this event characteristics similar, on a smaller scale, to rare historical solar storms, such as the Carrington Event of 1859. Although the impacts on the ground have been mitigated by technological infrastructure and modern monitoring systems, the episode reinforces the vulnerability of contemporary society to extreme phenomena originating from the Sun. As of the time of this publication, the end of the main phase of the geomagnetic storm has not yet been recorded, and disturbances are expected to persist for the next 24 hours.