The Solar Wind

The Solar Wind

Overview

  • The solar wind is a continuous stream of charged particles, made up mainly of electrons, protons and alpha particles with kinetic energy, released from the upper atmosphere of the Sun.
  • It was first proposed by the scientist Eugene Parker in the 1950s.
  • These particles escape from the Sun’s gravity due to the high kinetic energy they possess.
  • The solar wind differs from a solar flare, which is a burst of gas ejected from the sun’s surface, whereas the solar wind is a steady flow of particles.

Effects on Earth

  • Interactions between the solar wind and Earth’s magnetic field can create geomagnetic storms, which can cause beautiful auroras (northern and southern lights).
  • These interactions can disturb the Earth’s magnetic field causing problems with power grids, satellites and radio communications.
  • Prolonged periods of intense solar wind can also damage the atmosphere and contribute to its erosion over time.

Velocity and Composition

  • The solar wind does not blow uniformly, but has a variable speed and density.
  • There are two types of solar wind: the slow solar wind and the fast solar wind.
  • The slow solar wind is denser and slower, with speeds around 400 km/s, and is released from an area around the Sun’s equator.
  • The fast solar wind has speeds around 750 km/s and originates from coronal holes close to the Sun’s poles.
  • The composition of the solar wind across the heliosphere is roughly 90% hydrogen, 8% helium with the rest being trace amounts of heavier elements such as carbon and iron.

Detection and Study

  • Initially the solar wind was detected by observing the effects of solar energetic particles on cosmic rays.
  • The solar wind has been studied in more detail by spacecrafts like Ulysses, Voyager, and Parker Solar Probe.
  • Understanding the solar wind helps us to understand more about our Sun and the wider heliosphere.