Aurora Alert (May 14)

MAJOR SOLAR FLARE PROMPTS AN AURORA WARNING

The Sun is known for producing energetic spurts of activity, even during the less active periods around the solar sunspot minimum years. We are now a little more than one year from reaching the solar minimum. The frequency of energetic solar events has diminished over the last year, as has the number of sunspots that pepper the face of the Sun. But as has been the case with most solar cycles in recorded history, the Sun is not always quiet. It occasionally hiccups and produces large and complex sunspots capable of influencing space weather at the Earth.

We are currently experiencing one of those 'hiccups.' Several large sunspots have appeared recently that have had the potential to produce energetic solar flare activity. Region 10759, now nearing the central solar meridian, spawned a major class M8.0 solar x-ray flare at 16:57 UTC on 13 May. The event was associated with strong radio bursts across the spectrum. Such bursts have the potential to disrupt cellular phone services when the Sun is aligned with the direction of cellular signal propagation (most dominantly near sunrise and sunset when solar elevation angles are more in-line with cellular signal trajectories). This event has also been blamed for producing a weak space radiation storm, where energetic particles (protons) arrive from the Sun travelling at near relativistic velocities. Such storms have the potential to affect the health and stability of satellites orbiting the Earth.

Perhaps most significantly, this solar flare was associated with a coronal mass ejection that appears to be directed squarely at the Earth. Sometime on 15 May (perhaps during the early to mid UTC hours of 15 May, corresponding to the late evening to early morning hours of 14/15 May for North Americans), this cloud of solar plasma will impact the Earth's magnetosphere and energize it. What follows will depend upon the energy of the impact and the orientation of the embedded solar magnetic fields that interact with the Earth's magnetic field. If the embedded magnetic fields are oriented appropriately, they will generate a potentially strong geomagnetic storm and produce auroral activity ("northern lights") that may become visible across extensive middle latitude regions (central United States through perhaps central Europe, New Zealand and southern Australia).

Given our proximity to the solar minimum and the decreasing frequency of auroral storm events, it may be prudent to watch the skies carefully for activity this weekend (particularly on Saturday and Sunday nights). Current information can be found at www.spacew.com or www.sec.noaa.gov. Those who succeed in observing activity are encouraged to report their observations to the Global Auroral Activity Observation Network at: www.spacew.com/submitsighting.html. A near-realtime accounting of reported sightings can be found at: www.spacew.com/www/auroras.html.

This disturbance is expected to last roughly 18 to 24 hours and may only provide an opportunity to observe auroral activity for one evening. There may be additional opportunities to observe activity over the coming week, as the active sunspot complex responsible for producing this disturbance may yet spawn additional major flares and Earthward-directed CME's in the days ahead.