Come in Different Shapes
are long, gracefully curving
forms that extend from horizon
to horizon. Arcs and bands are
the most common auroral forms
seen by observers especially common during periods of low
solar activity. During moderate
to intense solar activity, they
become much more active and distorted.
band is similar to an arc but is
more curvy. Arcs can change into
bands over the course of a few minutes.
Bands are more gracefully curving
during low solar activity, but like
arcs become more distorted and active
during the Sun’s active periods.
corona is the name for an auroral shape in which the rays appear to converge
directly overhead. Coronas are also common during intense solar activity.
appear as smaller filaments or streaks.
They are formed when thin arcs curl
up on themselves, resulting in a
slightly brighter, quickly changing
structure. Rays are common during
high solar activity.
are just the most basic forms the aurora
can take. In reality, these lights in
the sky change from moment to moment, and
brighter during times of intense activity
in Earth’s magnetosphere. The shape
of an aurora depends partly on where
the aurora is occurring relative to the
observer, and partly on how Earth’s
constantly changing magnetic field responds
to the solar wind. If you are fortunate
enough to witness this cosmic light show,
remember that you are seeing visible evidence
of the particles that move along the lines
of Earth’s magnetic field.