Topic 10: Solar Astronomy

• H-Alpha filters absorb all sunlight apart from a narrow range of wavelengths
• T/△t = 360/△L
• Sunspots are regions of reduced surface temperature caused by a concentration of magnetic flux that inhibits convection
• The solar cycle is approximately 11 years long, with sunspot activity increasing to a maximum then decreasing again. They also move closer to the equator.
• Coronal mass ejections (CME) release large amounts of plasma from the corona into space.
• Core, radiative zone, convection zone, photosphere, chromosphere, transition region, corona
• The Corona's temperature is 2 million kelvin, it extends into space above the chromosphere and can only be seen during a total solar eclipse
• You cannot look directly at the Sun as it emits harmful UV and Infrared that can damage the eyes and even cause blindness
• Aurora is caused by the charged particles from the sun hitting the earth's atmosphere and ionising the air
• The Photosphere is 5800 kelvin and 100km thick
• The chromosphere is 100,000 kelvin and spherical
• The core is 15 million kelvin
• By observing the apparent motion of sunspots across the solar disc, it is possible to determine the Sun's rotational period at different latitudes and deduce that the Sun doesn't rotate as a solid body. Work out the longitudinal change of a sunspot over a period of time.
• Sunspots (cooler areas of the photosphere) are made up of the umbra (3800K) and the penumbra (5600K) and always form in pairs
• The Van Allen belts are two doughnut-shaped rings of charged particles trapped in the earth's magnetic field. The inner belt has an altitude of 1500-10,000km and contains mainly protons whereas the outer belt has an altitude of 15,000-65,000 and contains mainly electrons.
• The radiative zone is immediately above the core, energy is transferred outwards in the form of gamma radiation
• The convective zone is the outer 200000kn of the sun, thermal energy is transported by rising convection currents. At the base it is 2 million K whereas at the top it is 5800K
• Solar wind is a flow of charged particles (mainly protons and electrons) from the corona
• Solar wind causes:

  • Aurorae
  • Cometary tails
  • Geomagnetic storms
  • Effects satellites, aircraft travel and manned space missions
• Cometary tails occur when charged particles ionise gas to produce the ion tail of a comet
• Aurorae occurs when charged particles interact with the magnetosphere, which is strongest over the poles, to cause dazzling displays and curtains of light