DSCOVR and ACE sit about 1.5 million km sunward of Earth and report solar wind speed and the direction of the magnetic field it carries.
A southward field opens the magnetosphere; a northward one is shrugged off. Speed and Bz together say how hard the sky will actually be driven.
If the driving is strong enough to matter, a notification lands with the arrival time - typically 30 to 90 minutes out.
Minutes later the index climbs and the oval expands. By then you are already outside, looking north.
It shows the live KP index, an aurora oval map and a 3-day forecast, location aware - which is the same data aurora chasers use. Nothing can promise clear skies. See what the KP index is.
The ring around the magnetic pole where the lights are most likely to be visible - explained here. The app draws its current position on a map.
Yes, on Apple TV there is 4K northern lights footage, with alerts if you want to be told when activity rises.
Satellites measure the solar wind about 1.5 million km upstream, so a strong stream is detected while it is still in flight - typically 30 to 90 minutes before it reaches Earth. That is the alert you get on iPhone and iPad.
iPhone and iPad (iOS 17 or later) and Apple TV (tvOS 16 or later), with Home Screen and Lock Screen widgets and a Live Activity on iPhone.
No, and that is the usual reason an app disappoints. The same KP 5 puts the aurora overhead in Tromso and below the horizon in Berlin. The chance you see here is computed from your geomagnetic latitude, alongside how far you are from the edge of the oval in degrees and kilometres.
The live conditions screen, the widgets, the Live Activity and night vision mode are free. Tonight hour by hour, the 3-day outlook, the map, alerts, the compass, photo mode and Aurora School open with a single one-time purchase - no subscription, and one payment covers iPhone, iPad and Apple TV.
The app says "no data" rather than showing a plausible-looking number. Space weather comes from NOAA SWPC and the cloud, temperature and moon phase from Apple Weather; when one of them goes quiet you are told, because you may be driving an hour into the dark on the strength of it.
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