Electromagnetism

Discussion

introduction

Keep it historical and descriptive

The hand rules as I learned to number them. (The numbers are unimportant by the way.)

Oersted's observation of the field around a straight current carrying wire.

Move on to a loop of current carrying wire. Note how coiling the wire up produces a region of diverging field lines on one side (a north seeking magnetic pole) and a region of converging magnetic field lines on the other side (a south seeking magnetic pole). Introducing the solenoid.

The source of all magnetism is moving charge.

geomagnetism

This section is intended to be a discussion of magnetism on the large scale, not limited to the magnetic field of the earth (although that will be its primary focus). Perhaps this section should be title "megamagnetism".

start on the surface

The earth's magnetic poles are near but not on the geographic poles. [magnify]
The south magnetic pole is currently about one hundred kilometers north of Canada in the Arctic Ocean. The north magnetic pole is currently about one hundred kilometers north of eastern Antarctica in the Pacific Ocean.

work your way down into the earth

then work your way out into space


[magnify]

The effective reach of a celestial body's magnetic field is known as its magnetosphere. The earth's magnetosphere is compressed on one side and stretched out on the other by the solar wind. It extends about ten earth radii towards the sun and a thousand away from it.

Space weather

Real-time space weather information from the Space Environment Center of the US National Oceanographic and Atmospheric Administration (NOAA). What's the weather like in space right now?
Planetary K Index
Space weather is described by fluctuations in the earth's magnetic field and the speed and pressure of the solar wind. Values in the red indicate a geomagnetic storm is underway. The Kp Index shows the overall deviation of the earth's magnetic field for the last two to three days. Values in the red indicate a geomagnetic storm is underway (Kp > 4).
Northern Hemisphere Auroral ActivitySouthern Hemisphere Auroral Activity
Current auroral activity in the northern and southern hemispheres.
The red arrow shows the side of the earth facing the sun.

keep going out to the sun, then work out from the sun to the edge of the solar system

end with the galactic magnetic field

The Physics Hypertextbook

  • No condition is permanent.