Module 4
We are all familiar with ferromagnetism or the magnetic behavior of substances such as iron, nickel, and cobalt. These materials align the magnetic moments of their own atoms with an externally imposed magnetic field. In other words materials exhibiting ferromagnetism become magnetic themselves when exposed to an external magnetic field. Less familiar are paramagnetic and diamagnetic materials. Paramagnetic materials may become magnetized but do not retain a magnetic field as say an iron nail might. Diamagnetic materials actually align their internal magnetic moments in opposition to an externally imposed magnetic field.
Maxwell's equations are sufficient to describe the magnetic fields of refrigerator magnets, and even the intense fields required to levitate diamagnetic objects within high magnetic field laboratories. The situation becomes rapidly more complex when the materials and fields involved begin to self interact.It is thought that the Earth generates magnetic fields through a combination of convection of a molten core and the rotation of the planet. We have not successfully been able to simulate this process in part because the system is self- interacting, or non linear. This occurs because magnetic fields generated by currents in one portion of the Earth's interior begin to exert forces on and alter the motion of other convective currents elsewhere in the system.
To complete this discussion activity:
Do your own internet research, and then write an initial response to the following three discussion prompts. Post your response to the discussion board.
- What is the source of the Earth's magnetic field? In your response be sure to use the terms
dynamo theory, inner core, outer core, convection, and rotation. The Earth's magnetic field undergoes periodic reversals. How was this discovered, and by whom? What is the current best theory of its cause? How does the magnetosphere interact with charged particles in the solar wind? What happens to a planet without a planetary magnetic field, e.g. Mars?