Space weather refers to the environmental conditions in space that affect Earth and its technological systems. The main cause of space weather is the Sun, which constantly releases subatomic particles and electromagnetic waves.
Summary of Space Weather
It’s not always accurate, but most people think of space weather as what you would see on a cloudless day when the Sun is out, with perhaps only wispy clouds crossing the sky. Some of those puffs of clouds are actually high-level forms of matter called plasmas. Other “clouds” are made up of charged particles, electrons, or ions that move very fast at around 186,000 miles per second (300 kilometers per second). These speedy particles can produce dramatic effects near Earth if they hit our planet or if our planet hits them.
Space weather including geomagnetic storms and solar radiation storms can affect people and things on Earth, in space, and in aeroplanes.
Space Weather Affects Life on Earth
The Sun is constantly emitting a stream of charged particles that moves out through the Solar System at around 550 kilometers per second (about 300 miles/second). The particles are mostly electrons, but they carry so much energy that when they hit atoms or molecules in the near-Earth environment, the atoms’ outer electrons get knocked away from their nuclei, leaving these ions newly ionised. Collisions between spacecraft and high-speed matter are called hypervelocity impacts. They have become recognized as a serious threat to spacecraft.
At times, these ionised particles move along the Earth’s magnetic field lines and reach the upper atmosphere over the polar regions where they become super-excited and glow brightly in beautiful displays of light known as the aurora. They can also collide with molecules high in our atmosphere, releasing photons that give us a milder form of aurora called an airflow.
The Sun also emits plasma clouds (coronal mass ejections) filled with both electrons and ions. These clouds travel at speeds of around 1 million miles per hour (450 kilometres/second). Sometimes this plasma catches up with the slower-moving charged particles on their way toward Earth; sometimes it flows past or around them, and sometimes it slams directly into the Earth (where we feel its effects as geomagnetic storms).
Strong geomagnetic storms can knock out electrical power supplies, cause significant damage to satellites, disrupt communications on Earth through ground-induced currents, and produce strong currents in pipelines. The most powerful solar radiation storm of this century occurred during a geomagnetic storm when there was an intense mass ejection from the Sun.
Field Line Resonances
The greatest direct effect is strong electrical current flowing along paths called “field line resonances” in the ionosphere. This current flow excites a naturally existing mode of oscillation that pushes electrons toward and then away from Earth along the magnetic field (the field-aligned currents, or FACs). The electrons travel as much as 18,000 miles (30,000 kilometres) in a second. As they move toward Earth and then recede into space again they emit radio waves that interfere with low-frequency communications between submarines and their bases on land.