Meet the Cast: What Counts as a Solar Storm?

“Solar storm” is a catch-all term for several solar and geospace phenomena that sometimes occur together:

• Solar flares: bursts of light and high-energy radiation from the Sun’s atmosphere.
• Coronal mass ejections (CMEs): giant clouds of magnetized plasma hurled into space—sometimes billions of tons worth.
• High-speed solar wind streams: fast flows from coronal holes that can buffet Earth every 27 days or so.
• Solar energetic particles (SEPs): near‑relativistic protons and electrons accelerated by flares or CME shock fronts.
• Geomagnetic storms: disturbances in Earth’s magnetic field when the solar wind’s magnetic field couples strongly to ours.

Extreme Records and “Wait, What?!” Moments

• White-light flares are real: Most flares shine brightest in X-rays and ultraviolet. Rarely, a flare is so intense it brightens the Sun’s visible surface. The first was sketched in 1859 by Richard Carrington—hours before telegraph systems on Earth sparked, failed, and sent messages without batteries.
• The Carrington Event isn’t the only giant: The 1921 “Railway Storm” disrupted communications and set fires in telegraph offices. The Halloween Storms of 2003 triggered power outages in Sweden and spectacular auroras across mid-latitudes.
• A near miss in 2012: A CME as potent as the 19th‑century giants roared through Earth’s orbit—but our planet wasn’t there at the time. Spacecraft off to the side measured it. “What ifs” in space weather are very real.
• Ancient tree rings keep score: Spikes in radiocarbon in tree rings around 774–775 CE and 993–994 CE point to extreme solar particle events—possibly even stronger than modern recorded storms.
• The Sun has “quakes” and “tsunamis”: Some flares launch ripples across the solar surface (sunquakes), and massive eruptions can drive sweeping waves through the corona—nicknamed solar tsunamis.
• Fastest human‑made object? NASA’s Parker Solar Probe, designed to sample the Sun’s outer atmosphere, has become the fastest spacecraft ever, whizzing through the corona while withstanding intense space weather conditions.
• Comet tails can be torn off: CMEs can “disconnect” a comet’s ion tail. In 2007, a CME sliced away Comet Encke’s tail in dramatic fashion.

Auroras: Beyond Green Curtains

The aurora is a shape‑shifter. Charged particles guided by Earth’s magnetic field light up oxygen and nitrogen high above us, producing colors and forms with their own backstories.

• Colors are altitude clues:
  • Green (most common): oxygen around 100–150 km.
  • Red: oxygen above ~200 km, often during strong storms.
  • Blue and purple: molecular nitrogen emissions, lower altitudes.
• STEVE isn’t a classic aurora: Discovered by citizen scientists and named “STEVE” (Strong Thermal Emission Velocity Enhancement), it looks like a mauve ribbon spanning the sky. It’s linked to fast subauroral ion drifts rather than typical auroral precipitation.
• Picket fences, pulsations, and dunes: Auroras can flicker, pulse, or form tidy vertical stripes. In recent years, observers have even spotted “dune aurora,” thought to trace atmospheric wave structures illuminated by auroral glow.
• Aurora sounds? Reports of faint crackles or hisses near intense displays are rare and controversial, but controlled studies have occasionally captured coincident sounds under special atmospheric conditions. The debate continues.
• Equatorial auroras happen: During exceptional storms (like 1859 or 1872), auroras have been seen near the tropics—glowing over Cuba, Jamaica, and even Bombay (Mumbai).
• Polar “space hurricanes”: Spiral-shaped plasma vortices in the ionosphere, observed over the polar caps, can produce aurora-like signatures even under relatively quiet solar wind, defying expectations.

Odd Earthly Side Effects

• Telegraphs ran on “aurora power”: During the 1859 superstorm, operators reported sending messages after disconnecting their batteries—currents induced in long wires did the work.
• Power grids can hiccup: Geomagnetically induced currents (GICs) can saturate transformers. In March 1989, a severe storm collapsed the Hydro‑Québec grid in seconds, causing a nine‑hour blackout for millions.
• Railways and pipelines feel it too: GICs can trip railway signals and accelerate corrosion in long pipelines by altering their electrical potentials.
• Satellites get dragged down: Storms heat and puff up the upper atmosphere, increasing drag. In February 2022, a geomagnetic storm doomed dozens of newly launched satellites that couldn’t climb fast enough.
• Skylab fell early: The U.S. space station’s reentry in 1979 was hastened by higher-than-expected atmospheric drag tied to rising solar activity.
• GPS and radio go wonky: The ionosphere can scintillate, degrading GPS accuracy and disrupting high-frequency radio. Strong X-ray flares can cause sudden “daylight” radio blackouts on the sunlit side of Earth.
• Airlines re-route: On polar routes, airlines may divert during radiation storms to reduce passenger and crew exposure and to maintain reliable communications.
• Birds and magnetism: Studies have found that homing pigeons and other magnetically sensitive animals can become disoriented during geomagnetic disturbances, hinting at a subtle biological tie to space weather.

How We Forecast Space Weather (and the Secret Handshakes)

Space-weather watchers use a toolbox of indices and spacecraft to assess risk and predict impacts.

• Kp index: A 0–9 scale indicating global geomagnetic activity. Values of 5+ mark storm conditions; aurora hunters cheer when it climbs.
• NOAA scales: G1–G5 (geomagnetic), R1–R5 (radio blackouts), S1–S5 (radiation storms). Bigger numbers mean bigger headaches—and occasionally bigger auroras.
• Dst and AE: Dst tracks the ring current’s strength (more negative during big storms); AE reflects auroral electrojet intensity.
• L1 sentinels: Spacecraft like DSCOVR (and older ACE) sit sunward of Earth, sampling the solar wind. A sharp southward turn of the interplanetary magnetic field (negative Bz) is a classic “brace yourself” sign.
• Solar eyes: Space observatories (SDO, SOHO, Solar Orbiter) watch flares and CMEs, while Parker Solar Probe dips into the corona to study the physics at the source.
• Citizen science rocks: Projects like Aurorasaurus collect real-time aurora reports to improve alerts and map how far equatorward the lights are visible.

Solar Storms Across the Solar System

• Jupiter’s auroras dwarf ours: Fed by volcanic material from its moon Io and wrangled by a giant magnetosphere, Jupiter’s auroras blaze in ultraviolet with power outputs far exceeding Earth’s.
• Mars has patchwork auroras: Without a global magnetic field, Mars sports auroras over regions with remnant crustal magnetism. During strong solar storms, “global” diffuse aurora can occur.
• Mercury’s sodium tail: Space weather can enhance the planet’s long, comet-like sodium tail, visible to specialized instruments.
• Exoplanet hints: Astronomers are searching for space weather signatures around other stars; intense stellar activity could sculpt exoplanet atmospheres and magnetospheres.

Numbers to Make You Blink

• Speed demons: Fast CMEs can race outward at over 2,000–3,000 km/s; energetic particles can reach Earth in under an hour.
• Big masses: A single CME can carry billions of tons of solar plasma, threaded with magnetic fields that do the real geospace mischief.
• Aurora altitudes: Most displays glow between ~100 and 300 km up—far above weather and airplanes, but below many satellites.
• Cycle rhythms: Sunspots wax and wane on roughly an 11‑year cycle. Solar maximum brings more flares and CMEs; coronal holes and recurrent storms feature throughout the cycle.
• Double peaks: Many solar cycles show two maxima separated by months—the Sun is a complex orchestra, not a metronome.

Timeline Highlights

• 1859: Carrington Event—first observed white-light flare; telegraph disruptions worldwide; auroras seen in the tropics.
• 1921: Major storm knocks out communications; fires in telegraph exchanges; intense low‑latitude auroras.
• 1989: Québec blackout; widespread satellite anomalies; bright mid‑latitude auroras.
• 2003: Halloween Storms—satellite issues, aviation reroutes, Sweden power outages, extraordinary aurora displays.
• 2012: Earth dodges a Carrington-class CME that barrels through our orbit days after we pass by.
• 2022: Geomagnetic storm increases drag and leads to the loss of newly launched satellites in low Earth orbit.

Myths, Misconceptions, and Smart Caution

• Do solar storms cause earthquakes or volcanic eruptions? There’s no robust evidence linking solar storms to seismic or volcanic activity. The mechanisms and timescales don’t match.
• Are people on the ground at risk? Not from radiation—the atmosphere is an excellent shield. Risks are technological: power grids, navigation, aviation, and satellites.
• Can we “turn off” the Sun’s effects? No—but we can harden systems, plan operations, and forecast hazards to reduce risk.

How to Enjoy Solar Storms Safely

• Chase the lights: Watch for Kp 5+ and a sustained southward IMF (negative Bz). Go to dark skies with a clear northern or southern horizon, depending on hemisphere.
• Bring a camera: A tripod and a few‑second exposures can reveal colors invisible to your eyes.
• Try backyard science: Simple magnetometers (even DIY setups using a magnet and laser pointer) can show geomagnetic wiggles during storms. It’s space weather, made local.