What are Coronal Mass Ejections (CMEs)?

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What are Coronal Mass Ejections (CMEs)? Blog Image


An Indian Institute of Astrophysics (IIA) team along with their international collaborators recently developed a new model of the internal thermal evolution of coronal mass ejections (CMEs), as they travel from the sun toward the earth.

About Coronal Mass Ejections (CMEs):

  • CMEs are large expulsions of plasma and magnetic field from the sun's atmosphere—the corona, that propagate outward into interplanetary space.
  • During a CME, the sun releases a colossal amount of material, including electrons, protons, and heavier ions, as well as magnetic fields.

How are they formed?

  • They form similarly to solar flares—a result of the twisting and realignment of the sun's magnetic field, known as magnetic reconnection.
  • When magnetic field lines "tangle" they produce strong localized magnetic fields which can break through the surface of the sun at active regions, subsequently generating CMEs. 
  • CMEs usually take place around sunspot groups and are often accompanied by a solar flare, though the two don't always occur in tandem
  • CMEs travel outward from the sun at speeds ranging from slower than 250 kilometers per second (km/s) to as fast as 3000 km/s. 
  • The fastest Earth-directed CMEs can reach our planet in as little as 15-18 hours
  • They expand in size as they propagate away from the Sun, and larger CMEs can reach a size comprising nearly a quarter of the space between Earth and the Sun by the time they reach our planet.
  • CMEs, like solar flares, are most common during the solar maximum, a period in the sun's 11-year cycle of activity when the star is at its most active.

Impact on Earth:

  • Geomagnetic Storms: The interaction between the CME's magnetic fields and Earth's magnetosphere can lead to geomagnetic storms. These can disrupt satellite communications, navigation systems, and even power grids.
  • Auroras: CMEs can cause spectacular displays of the Northern and Southern Lights, also known as auroras, by energizing particles in Earth's atmosphere.
  • Radiation Hazards: Astronauts in space or passengers on high-altitude flights can be exposed to elevated levels of radiation during a CME event.

Key Facts about Solar Flare:

  • It is an intense burst of radiation coming from the release of magnetic energy associated with sunspots.
  • Flares are our solar system’s largest explosive events
  • They are seen as bright areas on the sun, and they can last from minutes to hours.
  • In a matter of just a few minutes, they heat the material to many millions of degrees and produce a burst of radiation across the electromagnetic spectrum, including from radio waves to x-rays and gamma rays.
  • Although solar flares can be visible in white light, they are often more readily noticed via their bright X-ray and ultraviolet emissions.

Effect of Solar Flare on Earth:

  • The intense radiation emitted during a solar flare can affect satellite communications, disrupt radio signals, and even pose a risk to astronauts in space.
  • Additionally, the increased solar radiation can lead to geomagnetic storms, which may impact power grids and cause auroras (northern and southern lights) at lower latitudes.

Q1: What are Sunspots?

Sunspots are dark, planet-size regions of strong magnetic fields on the surface of the sun. They can spawn eruptive disturbances such as solar flares and coronal mass ejections (CMEs). These regions of the sun appear darker because they are cooler than their surroundings.

Source:IIA develops new model of internal thermal evolution of coronal mass ejections