Solar Activity

The Sun is not just a big bright ball. It has a complicated and changing magnetic field, which forms things like sunspots and active regions.

The magnetic field sometimes changes explosively, spitting out clouds of plasma and energetic particles into space and sometimes even towards Earth.

The solar magnetic field changes on an 11 year cycle. Every solar cycle, the number of sunspots, flares, and solar storms increases to a peak, which is known as the solar maximum. Then, after a few years of high activity, the Sun will ramp down to a few years of low activity, known as the solar minimum. This pattern is called the “sunspot cycle”, the “solar cycle”, or the “activity cycle”.

The regions overlying sunspots are called active regions. Here the sun’s magnetic field becomes concentrated and twisted because of the motions of the solar atmosphere at and below the solar surface. As these regions become more complex they can eventually become unstable causing the release of the magnetic energy. This is analogous to twisting a rubber band tighter and tighter until it snaps releasing energy in the form of heat and motion. The same thing happens in the solar atmosphere with the active region magnetic fields. This release of energy heats up and accelerates solar material.

Solar Wind

The outer corona is heated up to such high energies that it eventually expands away from the Sun as a stream of electrons, protons and other atomic particles. The stream travels away from the Sun at speeds of around 200-400 km/s but can reach speeds of 900 km/s. The solar wind fills the entire solar system so all the planets sit inside the outer solar atmosphere. We live inside the atmosphere of a star. Sometimes concentrated high-speed solar wind streams come from the Sun and impacts the Earth. These can produce magnetic disturbances in the Earths upper atmosphere called a geomagnetic storm and produce the Southern and Northern Lights (The Aurora).

Solar Flares

Solar flares are a sudden, explosive release of magnetic energy in the form of electromagnetic radiation (most of the light spectrum, from radio waves to gamma-rays) and very fast atomic particles. Solar flares occur in regions of concentrated magnetic field such as sunspots.

Coronal Mass Ejections (CMEs)

Sometimes when magnetic energy is released the corona becomes so disturbed that large pieces of it are released into space. Billions of tons of solar material and magnetic field are hurled from the Sun into interplanetary space at speeds up to several million mph. As they move away from the Sun they expand becoming as wide across as the distance from the Earth to the Sun. CMEs can occur when filaments/prominences become unstable and fly away from the Sun. We call this a filament/prominence eruption.

Solar Energetic Particles (SEPs)

When a large solar flare or CME occurs they can accelerate a large number of atomic particles, electrons, protons and various elements to very high energies. When SEPs impact the cameras on a spacecraft the recorded images look like a television screen with a lot of static or snow.

Magnetism Facts

  • All magnetic fields are produced by moving or spinning charged particles…somewhere
  • Lines of magnetic force do not actually exist.
  • Magnetic poles always come in pairs.
  • The strongest magnetic field in nature is from the magnetar star SGR 1806-20, which has been estimated as 800 trillion Gauss.
  • A typical galaxy like the Milky Way has a magnetic field strength of about 0.000003 Gauss.
  • A refrigerator magnet has a strength of 100 Gauss.
  • A sunspot can have a magnetic field with a strength up to 10,000 Gauss, but they live very short lives!
  • Most magnetic storms on Earth happen during the Equinoxes in March and September
  • The sun’s magnetic poles flip their location on the sun every 22 years, called the Hale Magnetic Cycle.
  • Earth’s magnetic poles reverse their geographic locations every 300,000 years. The last event happened 780,000 years ago.
  • Magnetic pole ‘reversals’ have no effect on the rotational poles of a star or planet.
  • The geographic location of Earth’s North Magnetic Pole is currently moving nearly due-North at a speed of 100 meters per day.
  • Earth’s magnetic field is declining in strength by 5% every century.
  • Depending on your rate and direction of motion, a pure magnetic field can be turned into an electric field and vice versa.
  • Magnetic fields and electric fields are aspects of a more basic field in nature called the electromagnetic field.
  • A toy magnet produces more force on a paperclip than the entire mass of Earth through its gravity.