Chahal's Gyan Ki Baat

DYNAMO THEORY: GENERATION OF EARTH’S MAGNETIC FIELD


What is Dynamo Theory?

  • The Earth gets its own magnetic field lines due to the presence of the metallic fluids in the outer and inner core.
  • The outer core consists of molten iron.
  • The inner core has various solidified elements which are magnetic in nature.
  • The magnetism of Earth may be the result of particular structure of earth’s core.
  • The convection in the outer core in combination with the Coriolis effect due to the rotation of the earth gives rise to Earth’s magnetic field.


WHAT IS MECHANISM OF DYNAMO THEORY?

  • Earth’s magnetic field is generated in the low pressure outer core of the earth which is filled with fluid.
  • The temperature of the outer core ranges from 4400 °C to 6000 °C near the inner core.
  • Heat sources are
    • Energy released by the compression of the core.
    • Energy released at the inner core boundary.
    • Radioactivity of potassium, uranium and thorium
  • The difference in temperature, pressure and composition causes convection.
  • The cool and dense material sinks.
  • The warm and less dense matter rises in the outer core.
  • Eventually it turns into magnetic fields.
  • The spiral movement of the charged particles caused by the Coriolis force.
  • Charged metals passing through these fields go on to create electric currents of their own, this cycle continues.
  • This is ‘geodynamo’ a self-sustaining loop.


WHAT ARE DRAWBACKS OF DYNAMO THEORY?

  • The theory unable to explain fluctuations in magnetic field and reversal of polarity.
  •  It unable to explain the reasons responsible for changing position of magnetic poles were not discussed.