Sky & Telescope - May 2024 - 26

ALL IMAGES COURTESY OF THE AUTHOR
AURORA HUNTING by Marybeth Kiczenski
Chasing
T
he aurora borealis and its southern cousin, the aurora
australis, are considered among the most incredible
phenomena a person can witness without optical aid.
Standing under a clear sky while watching the green and red
curtains of auroral light shimmer and dance above is often
described as a beautiful, awe-inspiring, and even life-changing
experience.
Unsurprisingly, these ethereal lights are a major driver of
tourism in northern locations, such as Iceland and Norway.
But they aren't an ever-present phenomenon, at least from
places you can easily get to. You can book a trip to see them
and end up not catching so much as a brief display. That
leaves us with a few questions. How do you know when to
look for them? Are they predictable? And, for many of us,
how do you photograph them?
Right now we're entering the period of solar maximum,
the part of the Sun's 11-year cycle of activity with increased
sunspots and other active regions crackling with the energy
that trigger geomagnetic storms. Here are some tips on how
you can improve your chances of seeing and imaging these
ethereal displays.
Space Weather and Earth
Aurorae are a natural-light display
primarily seen at high latitudes. They
are caused by disturbances in Earth's
magnetosphere as it interacts with the
continuous stream of charged particles
the Sun releases known as the solar
wind. These particles are typically funneled
into the magnetosphere at high
latitudes where they form an auroral
ring around our planet's geomagnetic
poles (called the auroral oval). But at
times, disturbances in the solar wind
due to coronal holes (where charged
particles escape from the Sun faster)
and coronal mass ejections (CMEs) send
bursts of plasma into space, which can
impact our magnetosphere and trigger a
26 MAY 2024 * SKY & TELESCOPE
Here's how to improve
your chances of seeing
and photographing the
aurora borealis.
the Magic
geomagnetic storm, expanding the auroral oval away from the
polar regions (S&T: Oct. 2023, p. 74). When this happens, we
are treated to a fantastic display of aurorae farther south.
The colors of the aurora depend on which gas is being
affected and their altitudes. Most often, a display appears
green due to the charged particles interacting with oxygen
roughly 100 to 110 kilometers (60 to 70 miles) above. Less
frequently, these green curtains are topped with a deep-red
color - this is also due to oxygen, though at higher altitudes
of some 200 or 300 km.
There are also blue and purple aurorae, which come from
nitrogen being excited at lower altitudes. Much rarer are yellow
and pink ones, which are a mixture of red aurorae with
green and blue ones.
Tracking Aurorae
Aurorae are somewhat unpredictable - often conditions seem
perfect for a display, but it doesn't happen. So how can you
plan to see one? These days, we have access to an entire suite
of data that can help us determine if we have a better chance
of seeing geomagnetic activity. Most of
the information that space weather sites
and apps utilize comes from the Space
Weather Prediction Center (SWPC) at
swpc.noaa.gov, which offers a broad
set of data products for space weather
collected from several satellites. But
the website is difficult to navigate and
interpret, so it's generally better to
use a smartphone app or website that
distills the most relevant data helpful
for aurora chasers. My favorite is
SpaceWeatherLive for Android and Apple
devices. Here's a super simple guide on
how to interpret it.
In the app, the first thing it displays
CONTEMPLATING THE VIEW Two of the
author's friends enjoy a display from the shores
of Lake Erie, near Cleveland, Ohio, on February
26, 2023.
http://swpc.noaa.gov
Sky & Telescope - May 2024

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