Mon, 09 Jul 2012 13:55 CDT
July 9th began with a brief but beautiful display of auroras over North America. "I had gone out to search for noctilucent clouds
, but instead I found these Northern Lights," says Robert Snache of Rama First Nation, Ontario:
© Robert Snache
The source of the display was not an explosion on the sun, but rather a fluctuation in the interplanetary magnetic field (IMF). The IMF
near Earth tipped south, briefly opening a crack
in our planet's magnetosphere. Solar wind poured in and ignited the lights.
More auroras could be in the offing. A CME that left the sun on July 6th might deliver a glancing blow to Earth's magnetic field on July 9-10. NOAA forecasters estimate a 25% to 30% chance of polar geomagnetic storms if and when the cloud arrives.