Figure: Auroral ovals illustrated and explicated

Caption: A false-color ultraviolet image of an auroral oval (AKA auroral ring) over the Antarctica. The green false-color was probably chosen to mimic the actual green color of some aurora.

Features:

1. Original caption: "View of the aurora australis (southern lights), eight days after a record-setting solar flare sent plasma---an ionized gas of protons and electrons---flying towards the Earth. The ring of light that the solar flare generated over Antartica glows false-color green in the ultraviolet part of the electromagnetic spectrum, shown in this image. The IMAGE satellite observations of the aurora are overlaid onto NASA's Blue Marble image. From the Earth's surface, the ring would appear as a curtain of light shimmering across the night sky." (Slightly edited.)

2. The Earth's magnetic field lines converge at the magnetic poles of the Earth and intersect the Earth's in a circular pattern.
   Due to one of the great blunders of nomenclature history, the Earth's north magnetic pole (the magnetic pole in the north) and south magnetic pole (the magnetic pole in the south) are, respectively, a magnetic south pole and a magnetic north pole (see Wikipedia: Earth's magnetic field: Dipolar approximation). Just accept it.

3. The Earth's magnetic field lines are dragged with the rotating Earth.

4. The aurora are caused by charged paricles (mainly protons and electrons) in the solar wind.

5. The Earth's magnetic field is a barrier to the solar wind since charged particles tend to helix along magnetic field lines

   But the charged particles can move along the magnetic field lines , and so touch down usually in the Earth's atmosphere in the Earth's polar regions in the auroral zone in a pattern called an auroral oval such as in the image.

6. Through a rather complex process, the solar wind particles result in electrical currents (of ions and electrons NOT from the solar wind itself???) in the atmosphere that excite the air molecules (i.e., put them in high energy states). See Wikipedia: Aurora: Causes of auroras.

   The air molecules de-excite by emitting light.