Coronal Mass Ejections are huge bursts of magnetised plasma and magnetic field lines expelled from the Sun’s corona into outer space. They are among the most energetic events in the solar system and constitute a major component of space weather.

Nature & Composition

• Consist of electrons, protons, and heavier ions bound within strong magnetic fields.
• The plasma travels as a giant bubble (ejecta) carrying its own magnetic structure.
• Mass expelled in a single CME can reach billions of tonnes.

Formation Mechanism

CMEs originate due to magnetic reconnection — the breaking and rejoining of stressed magnetic field lines in the Sun’s corona.

Key steps:

• Intense twisting and stretching of solar magnetic fields near sunspots and active regions.
• Build-up of magnetic pressure creates instability.
• Sudden release of stored magnetic energy ejects plasma into space.

Though often linked with solar flares, CMEs and flares are distinct phenomena:

• Solar flares = bursts of electromagnetic radiation.
• CMEs = physical plasma clouds ejected outward.

Speed, Size & Frequency

• Typical speed: 250–1000 km/s
• Fast CMEs: up to 3000 km/s (reach Earth in 15–18 hours)
• Size: As they expand, large CMEs can grow to cover ¼ of the Earth–Sun distance.
• Strongly correlated with Solar Maximum – the most active phase of the 11-year solar cycle.

Types of CMEs (Based on Direction & Impact)

• Halo CMEs: Appear to surround the Sun when viewed from Earth; usually Earth-directed and most dangerous.
• Partial Halo CMEs: Spread over a smaller angular width; moderate impact.
• Narrow CMEs: Localised and generally less impactful on Earth.

Interactions With Earth

When Earth lies in the path of a CME, the plasma cloud interacts with Earth’s magnetosphere, compressing it and causing:

Geomagnetic Storms

• Disturbances in Earth’s magnetic field
• Increased electric currents in the atmosphere and ground

Potential Effects

• Satellites: Communication disruption, GPS errors, heating of satellite surfaces, orbital drag.
• Power Grids: Transformer overheating, voltage instability, large-scale blackouts (e.g., 1989 Hydro-Québec blackout).
• Aviation: Radio blackouts in polar routes.
• Forces on Pipelines: Accelerated corrosion due to induced currents.
• Auroras: Formation of auroras at unusually low latitudes — sometimes visible in India’s Ladakh, Kashmir, or Rajasthan during strong storms.

CMEs vs Solar Flares

Why CMEs Matter for Earth?

• Growing dependence on satellites, navigation systems, internet, and modern power grids makes CMEs a major technological hazard.
• They are crucial for space weather forecasting, essential for aviation, defence, and communication sectors.

Related Missions

• ISRO – Aditya-L1: India’s first dedicated solar mission to study CMEs, solar flares, corona, and solar wind.
• NASA – SOHO, STEREO, Parker Solar Probe: Provide real-time CME monitoring.
• ESA – Solar Orbiter: Helps map CME origins.