NASA Discovers New Sun-Earth Connection

Very interesting new findings from Science@NASA (also involving the Goddard Space Flight Center):

Spring is aurora season. For reasons not fully understood by scientists, the weeks around the vernal equinox are prone to Northern Lights. […] This is a bit of a puzzle. Auroras are caused by solar activity, but the Sun doesn’t know what season it is on Earth […]

Such outbursts are called auroral substorms and they have long puzzled space physicists. […]

NASA’s THEMIS mission–a fleet of five spacecraft launched in Feb. 2007 to study the substorm phenomenon […] may have found the substorm power supply–and a springtime connection:

The satellites have detected magnetic ‘ropes’ connecting Earth’s upper atmosphere directly to the Sun,” says Dave Sibeck, project scientist for the mission at the Goddard Space Flight Center. “We believe that solar wind particles flow in along these ropes, providing energy for geomagnetic storms and auroras.”

It turns out that rope-like magnetic connections between Sun and Earth are favored in springtime. It’s a matter of geometry: As Earth goes around in its orbit, Earth’s tilted magnetic poles make different angles with respect to the Sun, tipping back and forth with a one-year cadence. Around the time of the equinox, Earth’s magnetic field is best oriented for “connecting-up” with the Sun. […]

Geomagnetic disturbances are almost twice as likely in spring and fall vs. winter and summer, according to 75 years of historical records […]