G4severe
The geomagnetic storm of 24 – 27 July 1981
On 24 – 27 July 1981 the Kp index reached 8+: a G4 (severe) storm, with 45 hours at Kp 5 or more. At its peak the lights could be seen from 665,735 places in the atlas, down to about 44° magnetic latitude.
Kp 8+Peak Kp · 25 July 1981 12:00 UT
45Hours at Kp 5 or more
236Largest ap
Solar cycle 21Year 6 of solar cycle 21
Kp every three hours
56789
23 Jul24 Jul25 Jul26 Jul27 Jul28 Jul
Where the lights could be seen
At Kp 8+ the lights reach 665,735 places of the atlas on the horizon and 372,056 overhead, down to about 44° magnetic latitude.
The largest towns that could see them
MoscowRussia · 13.3MNew York CityUnited States · 8.8MLondonUnited Kingdom · 8.8MSaint PetersburgRussia · 5.65MMelbourneAustralia · 5.35MBerlinGermany · 3.7MKyivUkraine · 2.95MTorontoCanada · 2.79MBrooklynUnited States · 2.74MChicagoUnited States · 2.73MQueensUnited States · 2.41MMinskBelarus · 2MMontrealCanada · 1.9MHamburgGermany · 1.87MWarsawPoland · 1.86MManhattanUnited States · 1.69MNovosibirskRussia · 1.64MPhiladelphiaUnited States · 1.6MThe BronxUnited States · 1.47MYekaterinburgRussia · 1.47MKharkivUkraine · 1.42MPragueCzechia · 1.4MKazanRussia · 1.33MCalgaryCanada · 1.31M