G4severe
The geomagnetic storm of 22 – 23 August 1939
On 22 – 23 August 1939 the Kp index reached 8−: a G4 (severe) storm, with 39 hours at Kp 5 or more. At its peak the lights could be seen from 596,248 places in the atlas, down to about 46° magnetic latitude.
Kp 8−Peak Kp · 22 August 1939 00:00 UT
39Hours at Kp 5 or more
179Largest ap
Solar cycle 17Year 6 of solar cycle 17
Kp every three hours
56789
21 Aug22 Aug23 Aug24 Aug
Where the lights could be seen
At Kp 8− the lights reach 596,248 places of the atlas on the horizon and 298,213 overhead, down to about 46° 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 · 1.42MKazanRussia · 1.33MCalgaryCanada · 1.31MAstanaKazakhstan · 1.24M