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Northern Lights: Space Weather

Our daily lives on Earth are shaped by changing conditions that we call weather. Conditions in outer space change as well, and often times space conditions can affect things on Earth. So we monitor space weather.

You can monitor the current space weather online. This left column of this website provides up-to-date information about active regions on the Sun, the solar wind, the position of the current aurora oval, predictions of solar flares and geomagnetic storms. All of these factors influence when and where the Northern Lights are most likely to occur.

  • Plasma
  • Solar Wind
  • Geomagnetic Storms
  • Effects

Ionization

Plasma sphereIonization occurs when an atom gains or loses electrons, making it electrically charged. The atoms are negatively charged if they have more electrons than protorns and positively charged if they have more protons than electrons. Radioactive gases, ultraviolet light from the Sun, and cosmic rays have enough energy to knock electrons off of some atoms in our atmosphere, usually giving air atoms a positive charge and leaving a bunch of electrons free to fly around. An ion's electrical charge means that it is influenced by electric and magnetic fields.

Electricity

If you have ever seen a fleece blanket spark in the dark, had your hair stand on end, or "shocked" someone after walking on carpet, you have experienced an electric field. This static electriciy can build up in the atmosphere too. The free electrons are very light weight, and they are quickly accelerated by any developing electric field. This has a cascading effect that ionizes even more atoms and becomes a conducting pathway that emits light in the form of a spark, arc, or lightning.

LightningPlasma

Plasma is the state of matter composed of electrons and ions (charged particles). It is a state of matter that we don't encounter very often in our daily lives, but it is the most common state of matter in outer space. We are familiar with solids, liquids, and gases, but plasma is different. Plasma is made of atoms that are "ionized."

Some examples of plasma are lightning, material on the Sun, and the solar wind.

 

Solar Wind

The upper atmosphere of the Sun is very hot - millions of degrees. These high temperatures cause the atoms in the Sun's atmosphere to move very fast. Collisions at these high speeds are powerful enough to knock electrons off of atoms, ionizing them. Some of these charged particles are moving fast enough to escape the Sun’s gravity. This creates a constant outward stream of charges particles called the Solar Wind. There are two types of solar wind: the "slow"solar wind moves at 400 km/s and the "fast" solar wind moves at 750 km/s. This image shows the solar wind streaming outward from the Sun. A planet also happens to be in the view.

The charged particles in the solar wind sweep far out into space, well beyond the orbit of Pluto. They exert a constant pressure on the Eartht's magnetosphere, causing it to deform and bulge in the direction facing away from the Sun.

This animation shows how the Coronal Mass Ejection (CME) explodes from the Sun, carrying plasma toward the Earth. Our magnetosphere protects us by deflecting most of the charged particles around us, but as the night-time side of the magnetosphere gets stretched, the field lines break. The magnetic reconnection traps some CME particles, filtering them back to magnetic poles on Earth. This influx of charge sets up a ring current, in which the energetic particles excite oxygen and nitrogen atoms high in our atmosphere. The result is an oval of color, seen on the ground as the Aurora Borealis, or the Northern Lights.

Geomagnetic StormJust like weather on the ground, "space weather" can change daily, ranging from calm to stormy. Geomagnetic storms occur when CMEs arrive with a huge influx of plasma, distorting and shifting the Earth's magnetosphere. The magnetosphere field lines can stretch and break. Stronger geomagnetic storms push harder on the magnetosphere and stretch the oval out to lower latitutudes, giving low latitude observers a rare experience.

The space weather caused by geomagnetic storms can affect a variety of things, not only in the upper atmosphere, but on the ground as well. Since most space weather is driven by charged particles in plasmas, anything that uses electricity can be affected. At the edge of our atmosphere, the fast-moving, ionized particles smash into satellites, and even space shuttles and astronauts. This can tear apart the small scale structure of delicate equipment and even human cells, increasing an astronauts risk for cancer later in life.

As the charged particles plow their way down, the other charges particles in the Ionosphere try to resist and start to move. This creates an electric current in the ionosphere. Weak forms of electromagnetic radiation such as radio waves are blocked by this current, so you may notice that your radio program is distrupted or fuzzy, because those signals can't get to you.

Space Weather Effects

Check out NASA's education brief about Geomagnetic storms to learn more about the effects.