Level S4 solar radiation event

Aurora visibility and observations

• Many reports of strong aurora at unusually low latitudes: Berlin, northern and southern Germany, Netherlands, Ireland, Iceland, Austria, and parts of Australia (including Melbourne in a previous comparable storm).
• In big cities (e.g., central Berlin), aurora was still visible despite light pollution; others nearby saw nothing, highlighting how timing, clouds, and local lights matter.
• People compared naked-eye views vs camera: long exposures and phone HDR make structures and colors more prominent, but this event was often visible by eye.
• Shared webcam links (especially from Austria) showed dramatic displays; some debated whether streaks were Starlink satellites, planes, or long-exposure artifacts.

Timing, strength, and scales

• Confusion about the peak: some thought it had already passed; others noted Kp ~8–9 and that intensity could still rise.
• Discussion of G4 (geomagnetic) vs S4 (solar radiation) classifications; thread notes this event as S4 with high G-value.
• Context: ~100 G4 storms per 11‑year cycle, but they cluster around solar maximum, so not evenly “9 per year.”
• Comparisons to the Carrington Event and May 2024 storms; mention that Kp is capped at 9 and other indices (DST, HP30/60) capture higher intensities.
• Proton flux reportedly peaked around 37,000 pfu, close to historic highs.

Risk to people, aviation, and spaceflight

• For most people on the ground, consensus is “cool lights, low risk.”
• Airline radiation dose at high latitudes during G4 might be ~5–10× normal cruise dose but still well below occupational limits; some commenters feel that’s acceptable, others are wary.
• Spaceflight: concern about Artemis II; cited Apollo-era analyses and Orion’s contingency plan of building an improvised radiation shelter from stowage bags during a major storm.

Infrastructure, electronics, and preparedness

• Grid operators (e.g., PJM) issued geomagnetic disturbance warnings but did not reach alert/reconfiguration stages; no major North American grid issues reported.
• Technical explanation that geomagnetic storms mostly threaten very long conductors (transmission lines, pipelines), not small-scale home wiring or cars.
• Advice for homelabs/EVs: use surge protection/UPS; catastrophic transformer failures would dwarf any local equipment concerns.
• Some anecdotal glitches (router acting up, corrupted radio audio, a one-off memory error, a misbehaving consumer device) were observed but not conclusively linked.

Alerts, tools, and forecasting limits

• Recommended resources: NOAA subscription services, national aurora pages (e.g., Australian BoM), apps like “Aurora”/“Aurora Pro,” and global sighting trackers.
• Noted that Kp is a poor metric for Australia; local indices (e.g., KAus, G index) are more relevant.
• Highlighted that lead time for specific aurora visibility is often only 15–45 minutes once solar wind conditions are measured, so alerts are necessarily short-notice.

Communication and usability

• Strong criticism of the NOAA page for accessibility: key warning content embedded as an image/PowerPoint-like slide with no text alternative.
• An experimental aurora dashboard from the same agency was praised as more usable.

Attitudes and meta-discussion

• Mix of awe (“best aurora I’ve ever seen”) and regret from those who missed it.
• Some worry about Carrington-level scenarios and family preparedness; others characterize current G4/S4 storms as routine, manageable phenomena.
• General agreement that unless you’re an astronaut, aviator, grid operator, or HF radio user, this event is mainly notable for the sky show.