CME Tracking & Impact Prediction

Coronal mass ejections — CMEs — are the big one. When the Sun lobs a billion tonnes of magnetised plasma in our direction, that's what produces the strongest geomagnetic storms and the most widespread aurora displays. Lumina tracks CMEs from detection at the Sun all the way to impact at Earth.

Where the data comes from

Lumina pulls CME data from NASA's DONKI system (the Database of Notifications, Knowledge, and Information — a mouthful, but it's the best public-facing CME catalogue available). DONKI provides human-analyst-verified CME measurements including:

Speed, angular width, and direction from coronagraph imagery
WSA-ENLIL model runs — these are physics-based simulations that take a measured CME and model how it propagates through the inner solar system, predicting arrival time and intensity at Earth
Links to associated solar flares (if any)
Analyst notes and confidence assessments

Lumina checks DONKI every 30 minutes for new CMEs and updated model runs, looking back over a 5-day window to catch events still in transit.

Which CMEs make it to your timeline

Not every CME is worth worrying about. Lumina filters them by type:

Halo CMEs (width > 270°) — the CME appears as an expanding ring around the Sun in coronagraph images, which means it's heading roughly toward (or away from) Earth. These are the highest-priority events.
Partial halo CMEs (width 90°–270°) — still significant Earth-directed potential, especially if the CME source region was near the centre of the solar disk.
Fast CMEs (speed ≥ 800 km/s) — even if they're not halo events, extreme speed means high kinetic energy and a better chance of Earth impact.

Narrow, slow CMEs are filtered out — they're unlikely to reach Earth and would just clutter the timeline.

How Lumina predicts Earth impact

The WSA-ENLIL model is the workhorse here. For each CME, Lumina looks at all available ENLIL runs and checks three things:

Is Earth in the impact list? The most direct signal — ENLIL explicitly predicts an Earth arrival.
Is it a glancing blow? The CME might clip Earth rather than hitting head-on. Still worth watching, but typically produces weaker effects.
Is there an estimated shock arrival time? A non-null arrival time is the definitive signal that ENLIL thinks Earth gets hit.

Lumina also checks the reverse: if all ENLIL runs agree there's no Earth impact, the event gets downgraded to informational status rather than an active watch. This avoids crying wolf when a CME looks impressive but is headed somewhere else.

What the G-scale means

The NOAA G-scale is the standard way to classify geomagnetic storms. Lumina derives a G-level from the ENLIL-predicted Kp at Earth:

G-scale	Kp	What to expect
G1 — Minor	5	Aurora at high latitudes. Possible for Tasmania/southern NZ with good conditions.
G2 — Moderate	6	Aurora visible from southern Australia/NZ with clear skies. Worth heading out.
G3 — Strong	7	Aurora likely across much of southern Australia and all of NZ. This is a proper event.
G4 — Severe	8	Widespread aurora. Possible from Victoria, SA, southern WA. Don't miss this one.
G5 — Extreme	9	Extremely rare. Aurora possible from anywhere in southern Australia. Drop everything.

Event status lifecycle

Each CME in Lumina's system goes through a lifecycle:

Active — the CME is in transit or currently impacting. The predicted arrival hasn't passed yet (or is within a 24-hour window of arrival).
Resolved — the arrival window has closed. Either it came and went, or it was a miss. The event stays in the archive.

When a CME's shock actually arrives at Earth, Lumina can detect it in-situ from the solar wind data (a sudden jump in speed, density, and magnetic field strength). When that happens, the event gets an arrivalDetectedAt timestamp and the narrative updates to "A CME is currently impacting Earth."

Where you'll see CME alerts

Events page ( /events ) — the full timeline of all space weather events, filterable by type and severity.
Plan mode card — if an upcoming CME is within the 4-day planning window, you'll see a CME alert row with the predicted arrival time and expected intensity.
Aurora probability drivers — the CME driver row in the activity accordion shows the current impact status.