Aurora Surprise. A Gift From An Interplanetary Shock Wave.

CHANCE OF STORMS: NOAA forecasters estimate a 50% chance of polar geomagnetic storms on June 2nd as a high-speed (700 km/s) solar wind stream buffets Earth's magnetic field. The warning comes on the heels of a lengthy G2-class geomagnetic storm on May 31-June 1 sparked by the arrival of an interplanetary shock wave. The source of the shock is unknown. Current speculation focuses on a corotating interaction region (CIR)--that is, a shock-like transition zone between high- and low-speed solar wind streams. Whatever it was, the impact ignited some beautiful auroras, described below.

AURORAS IN THE USA: On June 1st, Northern Lights spilled across the Canadian border into more than a dozen US states, turning the sky purple and green as far south as Colorado and Nebraska. Subscribers to the Space Weather Alert System knew the storm was coming, but others were surprised:

"Last night, I drove to Crater Lake National Park to photograph the Milky Way rising above the rim," reports Oregon photographer Brad Goldpaint. "I was staring upward towards a clear night sky when suddenly, without much warning, the aurora borealis began erupting in front of me." (continued below)

"With adrenaline pumping, I raced to the edge of the caldera, set up a time-lapse sequence, and watched northern lights dance until sunrise," he continues. "The moon rose around 2am and blanketed the surrounding landscape with a faint glow, adding depth and texture to the shot."

High-latitude sky watchers should remain alert for auroras tonight as Earth's magnetic field continues to reverberate from the impact. NOAA forecasters estimate a 40% chance of polar geomagnetic storms on June 1st. 

Solar wind
speed: 774.7 km/sec
density: 1.4 protons/cm³explanation | more dataUpdated: Today at 1746 UT

source: http://spaceweather.com/

Interplanetary Shock Wave From Unknown Source Causing Strong Geomagnetic Storm

GEOMAGNETIC STORM: A G2-class (Kp=6) geomagnetic storm is in progress following the arrival of an interplanetary shock wave on May 31st. The source of the shock is not known; it might have been a minor CME that left the sun without drawing attention to itself. The impact sparked auroras across many northern-tier US states. This photo, for instance, comes from Christopher Griffith in Baxter, Minnesota:

"I wasn't expecting to see any lights, but right before the midnight it broke loose and the sky lit up," says Griffith. "Sadly the clouds quickly filled in my little window, and the auroras were gone. Just thankful for what I got so see!" Elsewhere in the USA, auroras were sighted as far south as Colorado, Maryland, Iowa, Wisconsin, andNebraska.

High-latitude sky watchers should remain alert for auroras tonight as Earth's magnetic field continues to reverberate from the impact. NOAA forecasters estimate a 40% chance of polar geomagnetic storms on June 1st.

source: http://spaceweather.com/

Space Weather Message Code: ALTK06
Serial Number: 308
Issue Time: 2013 Jun 01 1502 UTC

ALERT: Geomagnetic K-index of 6
Threshold Reached: 2013 Jun 01 1500 UTC
Synoptic Period: 1500-1800 UTC
Active Warning: Yes
NOAA Scale: G2 - Moderate
Potential Impacts: Area of impact primarily poleward of 55 degrees Geomagnetic Latitude.
Induced Currents - Power grid fluctuations can occur. High-latitude power systems may experience voltage alarms.
Spacecraft - Satellite orientation irregularities may occur; increased drag on low Earth-orbit satellites is possible.
Radio - HF (high frequency) radio propagation can fade at higher latitudes.
Aurora - Aurora may be seen as low as New York to Wisconsin to Washington state.

source: http://www.swpc.noaa.gov/alerts/archive/current_month.html