Where the aurora reaches, country by country
13 countries have towns the aurora reaches at Kp 6 or below, which is a storm that comes several times a year in an active part of the solar cycle. SWPC’s highest forecast Kp over the next three days is 2.
Towns are the world gazetteer’s: 15,000 people and up, each with a forecast page of its own.
Every country
With the geomagnetic latitude of its most poleward town, and the Kp that town needs.
- Icelandany night the sky is dark and clear at its far north70° geomag.
- Canadaany night the sky is dark and clear at its far north69° geomag.
- Norwayany night the sky is dark and clear at its far north68° geomag.
- RussiaKp 0.2 at its far north66° geomag.
- SwedenKp 0.3 at its far north66° geomag.
- FinlandKp 2 at its far north64° geomag.
- United KingdomKp 4.3 at its far north61° geomag.
- IrelandKp 5.4 at its far north58° geomag.
- DenmarkKp 5.5 at its far north57° geomag.
- EstoniaKp 5.6 at its far north57° geomag.
- LatviaKp 5.9 at its far north56° geomag.
- GermanyKp 6 at its far north55° geomag.
- LithuaniaKp 6.1 at its far north54° geomag.
The southern lights
The aurora australis rings the south magnetic pole, which sits off the coast of Antarctica at a geomagnetic latitude that puts almost every southern city out of reach: Hobart and Invercargill see it in a strong storm, Antarctic stations see it often, and nowhere else populated does. The same Kp table applies, read against southern geomagnetic latitude.
How far south each storm level reaches
NOAA’s space weather scales state the geomagnetic latitude each level of geomagnetic storm reaches, and the places its aurora has been seen from. The geographic latitudes are those lines converted with the geomagnetic dipole; the aurora sits low on the northern horizon there, and overhead far poleward of it.
| Storm | Geomagnetic | Central US | Eastern US | Northern Europe | NOAA says the aurora |
|---|---|---|---|---|---|
| G1 MinorKp 5 | 60° | 52°N | 51°N | 61°N | commonly visible at high latitudes: northern Michigan and Maine |
| G2 ModerateKp 6 | 55° | 47°N | 46°N | 56°N | has been seen as low as New York and Idaho |
| G3 StrongKp 7 | 50° | 42°N | 41°N | 51°N | has been seen as low as Illinois and Oregon |
| G4 SevereKp 8 | 45° | 37°N | 36°N | 45°N | has been seen as low as Alabama and northern California |
| G5 ExtremeKp 9 | 40° | 32°N | 31°N | 40°N | has been seen as low as Florida and southern Texas |
Source: NOAA space weather scales, swpc.noaa.gov/noaa-scales-explanation. Below Kp 5 the oval contracts more slowly; this section runs the line from 66 degrees geomagnetic at Kp 0 to the scale’s 60 degrees at Kp 5.
What this means
Each place is placed by its geomagnetic latitude, measured from the geomagnetic dipole pole, and compared with the reach NOAA states for each storm level on its space weather scales: G1 (Kp 5) about 60 degrees geomagnetic, G2 55, G3 50, G4 45, G5 (Kp 9) 40. Reading that backwards gives the Kp a place needs. Below Kp 5 the oval contracts more slowly and the line runs from 66 degrees at Kp 0 to 60 at Kp 5.
The forecasts have different horizons and the pages keep them apart: OVATION is the only thing that knows whether an aurora is out now, and it reaches 30 to 90 minutes ahead; the planetary Kp forecast runs three days; the 27-day outlook names likely active days and is not a forecast of any one night. None of them knows the clouds, which is why a town page reads its own forecast for those.
Sources
From NOAA’s Space Weather Prediction Center: the OVATION aurora forecast, the planetary K index forecast, the 3-day forecast, the 27-day outlook, its watches, warnings and alerts, and the real-time solar wind. Read Sep 20, 18:08 UTC.