G3strong
The geomagnetic storm of 21 May 1973
On 21 May 1973 the Kp index reached 7: a G3 (strong) storm, with 12 hours at Kp 5 or more. At its peak the lights could be seen from 512,587 places in the atlas, down to about 47° magnetic latitude.
Kp 7Peak Kp · 21 May 1973 06:00 UT
12Hours at Kp 5 or more
132Largest ap
Solar cycle 20Year 9 of solar cycle 20
Kp every three hours
56789
20 May21 May22 May
Where the lights could be seen
At Kp 7 the lights reach 512,587 places of the atlas on the horizon and 227,980 overhead, down to about 47° 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 · 3.7MTorontoCanada · 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 · 1.47MKazanRussia · 1.33MCalgaryCanada · 1.31MAstanaKazakhstan · 1.24MNizhny NovgorodRussia · 1.2MChelyabinskRussia · 1.18M