Solstice Sun Storm May Spark Dazzling Northern Lights Today

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Solstice Sun Storm May Spark Dazzling Northern Lights Today

by Tariq Malik, SPACE.com Managing EditorDate: 24 June 2011 Time: 01:53 PM ET

A wave of sun particles unleashed during a strong solar flare this week is

arriving at Earth today (June 24) and could touch off a dazzling northern lights

display, NASA officials say.

The solar storm occurred Tuesday, June 21, during Earth's solstice, which marked

the first day of summer in the Northern Hemisphere and the start of winter in

the Southern Hemisphere.

The storm triggered a powerful explosion on the sun, called a coronal mass

ejection, which sent a vast wave of solar particles directly at Earth at a speed

of about 1.4 million mph (2.3 million kph). Those particles are now buffeting

Earth's magnetic field in interactions that could amplify the planet's polar

auroras, also known as the northern and southern lights.

" High-latitude sky watchers should be alert for auroras, " officials with NASA's

Goddard Space Center said in an update today.

Supercharged auroras

Auroras occur when solar wind particles collide with atoms of oxygen and

nitrogen in Earth's upper atmosphere. The interaction excites the atoms, which

then emit light (the aurora) as they return to their normal energy level.

[Video: Fantastic Aurora at Earth's Poles]

Tuesday's solar flare registered as a class C7.7 flare (C-class flares are the

weakest types of flares), but lasted for several hours. There are three classes

of solar flares. M-class solar flares are medium-strength flares, while the most

intense solar storms register as X-class flares.

There is a 30 percent to 35 percent chance of a minor geomagnetic storm in

Earth's atmosphere today from this week's storm, NASA officials said.

The active sun

This week's solar flare was detected by the space-based Solar and Heliospheric

Observatory (SOHO) operated by NASA and the European Space Agency. It came just

weeks after another strong solar flare on June 7, which unleashed a massive

coronal mass ejection that stunned astronomers with its intensity.

The June 7 event kicked up a wave of plasma that rained back down on the sun

over an area 75 times the width of Earth. The leading edge of the particles that

erupted from the sun were traveling at about 3.5 million mph (5.7 million kph),

SOHO officials have said.

Another coronal mass ejection on June 14 unleashed an eerie wave of material

that formed a partial halo as it expanded into space.

The most severe solar storms, when aimed at Earth, can pose a danger to

astronauts in space, satellites and even ground-based communications and power

systems. This week's solar flare, however, is not powerful enough to pose a

serious risk, NASA officials said.

The sun is currently in an active period of its 11-year solar cycle. NASA and

other space and weather agencies are keeping a close watch on the sun using

space-based observatories, satellites and ground-based monitoring systems.