A strong solar flare erupted far beyond the Sun’s west limb around 18:00 UTC on November 21, producing a large coronal mass ejection and triggering a solar radiation storm on Earth.
According to the NOAA Space Weather Prediction Center (SWP), the flare was most likely produced by old Region 3989. The associated CME was first seen in LASCO C2 imagery at 18:12 UTC on November 21.
Since the CME originated well beyond the west limb, it is not expected to have an Earth-directed component.
However, proton flux counts started rising soon after the flare erupted and reached S1 – Minor solar radiation storm levels at 19:50 UTC on November 21.
S2 – Moderate levels were reached several times, starting at 01:05 UTC on November 22. The intensity of the storm has been decreasing since 07:00 UTC but is still in the S1 – Minor range, as of 15:40 UTC on November 22.
S1 solar radiation storms can cause minor impacts on HF radio in the polar regions and occur approximately 50 times per one 11-year solar cycle.
S2 – Moderate radiation storms can cause increased biological, operational, and communication impacts compared to S1 levels. Passengers and crew aboard high-altitude flights in polar regions may face an elevated radiation risk.
Satellite operations can experience infrequent single-event upsets under S2 conditions, potentially disrupting functionality. Additionally, small effects on HF radio communication and navigation systems may occur in polar cap regions.
S2 storms are less frequent than S1, occurring approximately 25 times per one 11-year solar cycle.
The NOAA Solar Radiation Storm scale ranges from S1 – Minor to S5 – Extreme, with S5 events being extremely rare, occurring fewer than once per solar cycle on average.
S5 solar radiation storms pose severe risks, including unavoidable radiation hazards for astronauts on extra-vehicular activity (EVA), potential HF communication blackouts, and catastrophic satellite failures, while less intense levels progressively impact biological safety, satellite integrity, and radio communications.
References:
1 Forecast Discussion – NOAA/SWPC – Issued at 00:30 UTC on November 21, 2024