STEREO - Solar Terrestrial Relations Observatory
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Space Weather

A solar storm, aurora from space, and aurora on Earth.
Space weather happens when a solar storm from the Sun travels through space and impacts the Earth’s magnetosphere.  Studying space weather is important to our national economy because solar storms can affect the advanced technology we have become so dependent upon in our everyday lives. Energy and radiation from solar flares and coronal mass ejections can:

  • Harm astronauts in space
  • Damage sensitive electronics on orbiting spacecraft…
  • Cause colorful auroras, often seen in the higher latitudes…
  • Create blackouts on Earth when they cause surges in power grids.

Understanding the changing Sun and its effects on the solar system, life, and society is a main goal of NASA's Heliophysics research program. Many NASA missions focus on the Sun and its interactions with Earth. Current missions include STEREO, SDO, SOHO, ACE, SORCE, and the Van Allen Probes.

Check the Current Space Weather.

Solar Cycle

The changing Sun produces sunspots and solar storms over an 11-year cycle of activity, which is driven by the reversal of its magnetic poles over this time period. Solar storms (coronal mass ejections and flares) occur most often and more powerfully during its period of solar maximum. The current solar maximum is expected to peak in 2012 or 2013.

The Sun in UV changing over 5 years
A century of sunspot number data
Animation: EIT 195 Large (QT, 5.2M) small (QT, 1.6M)

Solar Storms

There are two kinds of solar storms, often related to each other: coronal mass ejections (CMEs) and solar flares. A flare occurs when magnetic energy builds to a peak near the Sun's surface and explodes. This intense, fast-paced event results in an intense burst of light, including X-rays, in the Sun's lower atmosphere. A much larger storm, a CME erupts when magnetic field lines snap, sending billions of tons of material into space at millions of miles per hour. The cloud expands to over 30 million miles by the time it reaches Earth. Both flares and CMEs can result in additional high speed particles being shot out into the solar system at close to the speed of light.

Impact From Space

One beautiful sign of the space weather at the Earth is the aurora. When the CMEs from the sun interact with the Earth's own protective magnetic shield, its magnetosphere, the magnetosphere becomes disturbed. This ultimately causes charged particles to flow down along magnetic field lines into the polar regions where they hit the atmosphere and create the bright aurora. If viewed from high above Earth, these regions appear as ovals. Images taken by astronauts in the space shuttles show the depth of aurora. Other impacts from space weather include short-circuiting power grids that cause blackouts, disrupting communications, damaging satellites, and endangering astronauts with radiation.



Aurora appear from Earth as shimmering, dancing lights in the night sky. Only 100 years ago did scientists discover that the Sun was ultimately the cause of these mysterious lights. Although green is the most common color, red and yellow hues are also observed. The most powerful displays occur when large clouds of particles from CMEs slam into our magnetosphere, but the constant outpouring of solar particles (called the solar wind) can cause them as well.


Video Clips and Animations

Overview animation of solar storm and its impact on Earth
Extreme close-up of a sunspot in action, Swedish Solar Telescope large (QT, 3.9M), small (QT, 403k)
A particle blast close-up, EIT 304. large (QT, 2.2M), small (QT, 717k)

Flares and solar activity from late 2003 storms, EIT 195. large (QT, 10.4M), small (QT, 2.6M)
Close-up of a CME blasting off, EIT 195. large (QT, 1.9M), small (QT, 246k)
A busy week of solar activity, LASCO C2 large (QT, 7.2M), small (QT, 2.7M)

Weeks of solar activity from late 2003 storms, LASCO C3 large (QT, 7.7M), small (QT, 3.8M)
A light-bulb shaped CME, LASCO C3. large (QT, 1.6M), small (QT, 640k)
Solar streaming and CMEs from the Solarmax IMAX film. large (QT, 4.7M), small (QT, 821k)

Cascades of loops following a flare from TRACE. large (QT, 3.6M), small (QT, 530k)
Cascades of loops following a flare from TRACE. large (QT, 2.6M), small (QT, 359k)
Auroral oval observed from space by IMAGE. large (QT, 2.0M), small (QT, 148k)

Auroral ovals over the North Pole region from Polar. large (QT, 4.1M), small (QT, 1.7M)
Aurora in UV over both polar regions from Polar. (QT, 2.4M)
NASA animation of Earth's magnetosphere shaped by solar wind (QT, 3.4M)

Clip of aurora from the Solarmax IMAX film. large (QT, 1.2M), small (QT, 448k)

Space Weather Poster

Space Weather Poster Thumbnail

Launch Multimedia Presentation

Download the print version Space Weather poster.
(1.9 mb)

Download the Spanish version Space Weather poster.
(2.95 mb)


Last Revised: Saturday, 09-Feb-2013 16:03:25 EST
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