Space Weather

Space Weather is the term scientists use to describe the ever changing conditions in space. Explosions on the Sun create storms of radiation, fluctuating magnetic fields, and swarms of energetic particles. These phenomena travel outward through the Solar System with the solar wind. Upon arrival at Earth, they interact in complex ways with Earth's magnetic field, creating Earth's radiation belts and the Aurora. Some space weather storms can damage satellites, disable electric power grids, and disrupt cell phone communications systems.
A sinuous glowing band of <a
  href="/earth/Magnetosphere/aurora.html">aurora</a> (the Aurora Australis
  or Southern Lights) loops around the <a
  href="/earth/polar/polar_south.html">southern polar</a>
region in the
  distance as viewed by astronauts onboard the space shuttle on <a
  href="http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/archives/sts-39.html">STS-039</a>. 
  <a
  href="/earth/Magnetosphere/aurora/aurora_colors.html">Aurora are produced</a>
  when <a
  href="/physical_science/physics/atom_particle/particle_radiation.html">energetic particles</a>
 entering the Earth's
  atmosphere from space interact with <a
  href="/physical_science/physics/atom_particle/atom.html">atoms</a> and <a
  href="/earth/geology/molecule.html">molecules</a> in the atmosphere and
  release energy, emitted as light.<p><small><em>Courtesy of NASA, Astronaut Overmeyer and Dr. Hallinan</em></small></p>The outermost layer of the <a href="/sun/solar_atmosphere.html">Sun's atmosphere</a> is the <a href="/sun/atmosphere/corona.html">corona</a>.  The corona is very, very hot - about 1 million degrees!  Glowing <a href="/sun/Solar_interior/Sun_layers/Core/plasma_state.html">plasma</a>, which is like magnetized gas, sometimes forms loops in the corona. <a href="/sun/atmosphere/sunspot_magnetism.html">Magnetic fields around sunspots</a> make these loops, called coronal loops. The loops are huge - about 30 Earths would fit across them! A satellite named TRACE took this picture in November 1999.<p><small><em>Image courtesy of NASA/Trace Mission</em></small></p>Sunspots don't look that big when you see them on the Sun (remember NEVER look directly at the Sun), but in fact they can be enormous!  This composite image shows just how big sunspots can be, to scale with an image of Earth.  Sunspots can be as big, or bigger, than Earth.  The <a href="/sun/activity/sunspot_history.html">earliest written record of a sunspot observation</a> was made by Chinese astronomers around 800 B.C.<p><small><em>Image courtesy of Windows to the Universe using images from the Royal Swedish Academy of Sciences (sunspot image) and NASA (Earth image).</em></small></p>The <a href="/earth/Magnetosphere/overview.html">magnetic field of the
Earth</a> is
surrounded in a region called the magnetosphere, which is much larger
than the Earth itself. The magnetosphere prevents most of the particles from
the sun, carried in <a href="/sun/solar_wind.html">solar
wind</a>,
from hitting the Earth.<p><small><em> Image courtesy of Windows to the Universe.</em></small></p>On 21 April, 2010, the Solar Dynamics Observatory captured the launch of a filament from the <a href="/sun/atmosphere/photosphere.html">surface of the Sun</a>.  These are the most detailed images of the Sun ever taken.  The images show light in the <a href="/physical_science/magnetism/em_ultraviolet.html">ultraviolet</a> part of the <a href="/physical_science/magnetism/em_spectrum.html">electromagnetic spectrum</a>.  The Sun is now entering another period of <a href="/sun/solar_activity.html">solar activity</a> after several years of a relatively quiet Sun.  Activity on the Sun varies on an <a href="/sun/activity/sunspot_cycle.html">cycle of about 11 years</a>.<p><small><em>Image courtesy of NASA/Solar Dynamics Observatory and AIA Consortium</em></small></p>This is an artist's conception of the
  Earth and the inner and outer <a
  href="/glossary/radiation_belts.html">radiation belts</a> that surround it. The Earth's radiation belts are just one part of
  the system called the <a
  href="/earth/Magnetosphere/overview.html">magnetosphere</a>. The radiation belts of the Earth are made up of <a
  href="/physical_science/physics/atom_particle/electron.html">electrons</a>,
<a
  href="/physical_science/physics/atom_particle/proton.html">protons</a>
  and heavier atomic ions. These particles get trapped in the <a
  href="/earth/Magnetosphere/earth_magnetic_field.html">magnetic field of the Earth</a>. 
These belts were <a
  href="/earth/Magnetosphere/radiation_belts_discovery.html">discovered</a> by James Van Allen in 1958, and so they are known as Van Allen
  Belts.<p><small><em>Courtesy of Windows to the Universe</em></small></p>

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