Proton flux started sharply rising from 16:00 to 17:00 UTC on October 26 and exceeded the alert threshold level for S1 – Minor solar radiation storm by 19:10 UTC, possibly following the shock arrival from the long-duration X1.8 solar flare on October 26.
Flux values continued rising and reached the S2 – Moderate solar radiation storm threshold at around 08:30 UTC on October 27.
Following the sharp increase that led to the S2 – Moderate solar radiation storm threshold, elevated levels of both high-energy protons and electrons are forecasted to persist in the coming days.
S2 – Moderate solar radiation storms can lead to several impacts, especially for high-altitude and polar-latitude systems. Passengers and crew on high-flying aircraft, particularly on polar routes, may experience elevated radiation exposure, posing potential health considerations for frequent travelers or sensitive groups.
Satellite operations can face occasional single-event upsets, where high-energy particles disrupt electronic components, forcing resets or temporary adjustments by operators. Additionally, HF radio communications can suffer minor disruptions over polar regions due to ionospheric disturbances, which may also affect GPS signal accuracy and navigation reliability in these areas.
While S2 storms are relatively common, occurring about 25 times per solar cycle, these effects are generally manageable with appropriate precautions and operational responses.
The greater than 2 MeV electron flux is expected to remain at moderate to high levels through October 29.
This increase in high-energy electron levels is primarily due to the effects of the recent coronal mass ejection (CME) and an incoming coronal hole high-speed stream (CH HSS).
Elevated electron flux can result in surface charging on satellites, increasing the risk of operational disruptions for spacecraft in geostationary and medium Earth orbits.
Additionally, the 10 MeV proton flux is expected to stay above 10 pfu through early October 27, with a continued likelihood of exceeding threshold values over October 28 and 29.
This sustained proton activity suggests that minor solar radiation storm conditions could linger, potentially maintaining S1 to S2-level impacts through the period. This would mean intermittent disruptions to HF radio signals, particularly over polar regions, as well as minor GPS signal interference at high latitudes.
The long-duration X1.8 solar flare on October 26 was accompanied by Type II radio sweeps at an estimated speed of 486 km/s, Type IV radio sweeps, and a 4 200 sfu Tenflare, indicating significant energy release and plasma movement in the solar atmosphere.
CME associated with this event was primarily directed southeast. Although the CME appeared as an asymmetric, full-halo in coronagraph imagery, the initial analysis suggested that most of its material had a trajectory southward and behind the Sun-Earth line.
However, CME models indicated that Earth could experience a glancing blow from this event, expected to arrive early on October 28.
Solar wind conditions were mostly at background levels until 15:35 UTC on October 26, when a shock was detected in the solar wind data. This shock caused the total magnetic field (Bt) to increase from 10 – 14 nT to 22 – 26 nT, with the Bz component turning sharply southward, reaching -19 nT. Solar wind speeds also rose from approximately 375 km/s to around 505 km/s, while the phi angle remained positive.
This disturbance is likely linked to the arrival of CME associated with a halo CME produced on October 24.
Elevated solar wind conditions are expected early on October 27, gradually returning to nominal levels by the day’s end. More enhanced solar wind activity is anticipated on October 28 – 29 due to a negative polarity CH HSS and potential residual effects from the CME launched on October 26.
Geomagnetic conditions are forecasted to reach unsettled to active levels on October 27, with a potential for periods of G1 – Minor geomagnetic storms. This activity is likely due to the expected arrival of the CME produced during the long-duration X3.3 solar flare on October 24.
Unsettled to G1 – Minor geomagnetic storm conditions are anticipated on October 28, driven by a negative polarity coronal hole high-speed stream (CH HSS) and the possible glancing blow from the CME launched on October 26.
By October 29, unsettled to active geomagnetic levels are expected to persist, as effects from recent CMEs are likely to continue influencing Earth’s magnetosphere.
References:
1 Forecast Discussion –SWPC – Issued at 00:30 UTC on October 27, 2024