Play with the physics behind the aurora — the Sun's storms, Earth's magnetic shield, the colours and the heights they glow at, the Kp scale, and more. Drag, hover, and every figure responds.
01Kp index & auroral oval
Kp index & auroral oval
See how far the aurora descends from the north.
3
Kp 0 – 9
Active
calmstorm
At this Kp level the aurora can be seen from:
Tromsø · Norway · 69.6°N● visible
Reykjavík · Iceland · 64.1°N● visible
Oslo · Norway · 59.9°N○ —
Edinburgh · Scotland · 55.95°N○ —
İstanbul · Türkiye · 41°N○ —
Drag the slider — the oval descends from north to south, and cities light up as it reaches them.
02Earth's magnetic shield
Earth's magnetic shield
The solar wind leaks in through the poles.
The atmosphere is an immense shield. Most of the charged particles from the Sun are deflected at the bow shock and flow around the magnetopause; only those that leak through the polar cusps reach the atmosphere and create the northern lights.
Solar-wind particles are animated; most are deflected, and those that leak through the polar cusp create the aurora.
03Aurora colours and altitude
Why different colours?
Colour is the work of gas and altitude.
Green110–300 km · Oxygen
The most commonly seen colour. It forms when charged particles collide with oxygen at low altitude (≈100–300 km).
Blue and violet — the human eye often struggles to make out these colours, produced by hydrogen and helium gases.
Hover over a colour band.
Hover over a colour band — which gas, which altitude.
04Watching points — by country
Watch points since 2013
Norway17 locations%81
Iceland2 locations%10
Sweden2 locations%10
Built from the real watch-point data gathered since 2013.
05The 11-year solar cycle
Does the Sun sleep?
Eleven years, minimum to maximum.
year
202688%
Solar maximum
The Sun's activity rises and falls on an ~11-year rhythm. Near maximum, sunspots and solar storms are frequent and the aurora reaches far south; near minimum, quiet nights can pass with nothing at all.
Drag the year — activity swings from quiet minimum to stormy maximum over ~11 years. We're near a maximum now.
06The night viewing window
The ideal time
Darkness is the other half.
Moon illumination · 0%
Dark window
18:45 – 05:15
10.5 h
A clear, dark sky is half the battle. True (astronomical) darkness is the best window — but a bright moon lifts the sky's glow and eats into it. A new moon, or shooting before the moon rises, gives the deepest dark.
Drag the moon's brightness — a full moon washes out the sky and shrinks the truly-dark window.
07Anatomy of a substorm
0~2–3 h
Anatomy of a substorm
Quiet, breakup, and recovery.
The arc suddenly brightens and erupts — rays shoot up, the curtain surges poleward and folds into swirls. The fast, dramatic part most people picture as 'the aurora.'
The aurora doesn't burn steadily — it pulses through a substorm cycle. Patience pays: a quiet arc can erupt into a breakup in seconds.
Step through the phases — a quiet arc loads, erupts at breakup, then fades through recovery.