The Aurora Borealis

By Richard Bangma, Shea-lynn Farrell, Cree Longjohn and Yu Tu

Introduction

The aurora borealis, commonly known as the Northern Lights, is a distinctive feature of the Canadian skies and an important part of First Nations folklore. Scientists now know this brilliant natural light show is caused by particles from the Sun interacting with the Earth’s atmosphere, but what are the tools and methods they use to study this phenomenon?

On this website you can find some of the fascinating tales about the Northern Lights that the First Nations peoples have passed down through their intricate oral histories. You can find up-to-date information on what scientists currently know about the Aurora Borealis, as well as the tools and methods they use to expand their knowledge as they study it from Earth and in space.

First Nations Interpretations of the Aurora Borealis

Galileo is believed to be the first to apply the name aurora to the northern lights.  In 1619 he named it after Aurora, the Roman goddess of morning who appeared as a forerunner of the Sun prior to the start of each new day.¹ Before Galileo’s naming of the auroras, Canada’s First Nations’ people created oral stories, based on their beliefs, to interpret a phenomenon they observed and heard but didn’t understand, the northern lights. These stories have been passed down from generation to generation and have become enshrined in the Indigenous worldview of auroras we know today. The stories differed from region to region as did the names applied to the auroras, even though they all attempt to interpret the same phenomenon.

Translations of some Eskimo and American Indian names applied to the northern lights are: ball player, sky dwellers, that which moves rapidly, untimely birth, caribou cow, the old man, and dance of the dead.¹  The folklore that evolved to interpret what Indigenous Canadians saw and heard varied from region to region just as much as the names given to the northern lights. Examples of some Indigenous Canadian folklore interpreting the auroras are listed below.

• To the Ottawa Indians, the auroras were a great fire lit by the creator to remind them of his interest in their welfare.¹
• The Salteaus Indians of eastern Canada interpreted the northern lights as the dancing of human spirits.²
• The Inuit who lived on the lower Yukon River believed that the auroras were the dance of animal spirits, especially those of deer, seals, salmon and beluga.²
• The Chipewyan Dene interpreted the aurora borealis, or the “ed-thin”, meaning caribou, as the spirits of their departed friends dancing in the sky.  When the lights shined the brightest, it meant that their deceased friends were very happy. The Chipewyan Dene of Western Canada also believed that stroking caribou fur created sparks much like the aurora.⁴
• An Algonquin myth tells of when Nanahbozho, creator of the Earth, had finished his task of the creation, he traveled to the north, where he remained. He built large fires, of which the northern lights are the reflections, to remind his people that he still thinks of them.²
• The Inuit of Hudson Bay dreaded the lights, believing they were the lanterns of demons pursuing lost souls.²
• Indians of the Great Plains of North America thought the light display came from northern tribes who were cooking their dead enemies in huge pots over blazing fires.²
• If you whistled at the aurora, some Native Americans believed it would sweep down and take you away. Clapping your hands, however, caused the lights to retreat, keeping you safe.²
• When they witnessed the lights, many Inuit, the Arctic’s Indigenous peoples, believed they were spirits of the dead playing a game with a walrus skull as the “ball”.²
• The Chippewa Indians of central Canada said that the appearance of auroras were good because it meant that many deer were in the sky.¹

As you can see, there is quite a variety of Indigenous Canadian folklore created to interpret what was observed and heard.  It wasn’t until the nineteenth and twentieth centuries that scientific methodology was implemented to study and explain the phenomenon of the aurora borealis.

What Scientists Know about the Aurora Borealis

What are the auroras?

• Auroras in the northern hemisphere are called “aurora borealis” and auroras that occur in the southern hemisphere are called “aurora australis”.
• Both auroras appear as an irregularly shaped oval centered over their respective magnetic poles, in the area called the auroral oval.
• In most instances, northern and southern auroras are mirror-like images that occur at the same time, with similar shapes and colours.  Green is the most common colour occurrence in auroras, however, red, yellow, blue and violet are seen occasionally.
• Auroras can appear in many forms, from “patches of light that appear out of nowhere to streamers, arcs, rippling curtains or shooting rays”.⁶

What causes auroras?

Auroras are the result of collisions between gaseous particles in the Earth’s atmosphere with charged particles released from the Sun’s atmosphere.  The colour variations are due to the type of gas particles that are colliding.

• The most common color, green, is caused by oxygen molecules located about sixty miles above the Earth.⁶ Rarer red auroras are produced by high-altitude oxygen, at heights of up to two hundred miles above the Earth’s surface. Nitrogen produces blue or purple auroras.⁶

How do charged particles from the Sun get here?

Normal Solar activity frequently ejects electrons and protons to flow out (typically) and make contact with the Earth’s magnetosphere.

For auroras to appear, a lot of charged particles are needed from the Sun to collide with Earth’s atmosphere.  This usually requires quite a large opening, such as a coronal hole, or a Sunspot. This Solar prominences article contains a number of videos explaining how charged particles escape from the Sun.

• The connection between auroras and Sunspot activity has been suspected since about 1880.  Through research conducted in the 1950’s, we know that electrons and protons from the Sun are blown towards the Earth on the “solar wind”.⁶
• When these charged particles are blown toward the Earth by the solar wind, they are largely deflected by the Earth’s magnetic field.  However, the Earth’s magnetic field is weaker at the two magnetic poles and therefore some particles enter the Earth’s atmosphere and collide with gas particles.  These collisions emit light that we perceive as the dancing lights of auroras.
• These lights of auroras generally extend from eighty kilometers to as high as six hundred and forty kilometers above the Earth’s surface.⁶

Best place to watch auroras?

• Typically, watching from as close to one of the magnetic poles as possible will allow optimal viewing of auroras.
• With the north magnetic pole being located in Northern Canada, near Ellesmere Island, at about 80 degrees latitude or 20 degrees further south than the North Pole, the aurora borealis can be viewed further south on the western hemisphere than on the eastern hemisphere.³³
• Due to the location of the north magnetic pole, the aurora borealis is most easily viewed from northern Europe, Iceland, the southern tip of Greenland and the northern parts of Canada and the United States.⁶
• With the south magnetic pole being located on the tip of Antarctica closest to Australia, in theory, the aurora australis should be visible throughout much of Australia.³⁴
• Due to the location of the south magnetic pole, the aurora australis is most easily viewed from Antarctica, New Zealand or Australia.⁶
• Aside from proximity to the magnetic poles, other factors that affect viewing ability include:

• Light pollution will ruin an aurora show, so the best place is away from lights.  Typically in the north, driving as little as 30 minutes outside a city should eliminate light pollution.
• An unobscured view in northern direction (unless you’re so far north that auroras are directly overhead).  This also depends on Kp strength of auroras.
• The current Kp strength can be viewed at this Aurora Forecast page.
  

  Graphic showing Kp strength required to view auroras by location.
  Courtesy of Amazing Auroras.

• Kp Strength is a scale of geomagnetic activity consisting of numbers between 0-9, known as the planetary index.  Numbers start at 0 and as the geomagnetic (aurora) strength increases, so too does the Kp number.  Using this scale, it is easy to determine what Kp number you need to have a chance of seeing auroras where you are.
• Geomagnetic storms are labelled G1 to G5.  It is a period of strong to very strong geomagnetic activity due to a lot of buildup in Earth’s magnetotail which causes magnetic reconnection and snap back to occur. This accelerates a lot of particles back toward Earth (a natural particle accelerator if you will) which can spark really awesome northern/southern light displays.  Conversion of G into Kp:

• G1 = Kp5
• G2 = Kp6
• G3 = Kp7
• G4 = Kp8
• G5 = Kp9⁷
  

  Courtesy of NASA/Scott Kelly

• Of course, the International Space Station is also a good spot to view auroras!

Impact of auroras

Solar winds, enhanced by eruptions on the surface of the Sun, interact with Earth’s magnetic field and can create electrical currents with up to a million megawatts of power.⁹

• Auroras are but one symptom of a larger space weather system in which solar material and radiation can affect Earths own magnetic environment and block radio communication, disturb onboard satellite computers, or cause electrical surges in power grids.⁸
• A series of solar eruptions in August-September, 1859 produced electromagnetic disturbances at Earth’s surface so severe that telegraph equipment caught on fire and operators received painful electric shock.⁹

• A 2010 study by the Metatech Corporation (funded by NASA) indicated that if solar eruptions as large as the ones in 1859 occurred today, it would produce electrical blackouts affecting 40% of US households.⁹ The blackouts could last months while the affected households waited for destroyed electrical transmission and generation equipment to be replaced.⁹
• In 2010 there was such a solar eruption, but the active region of the sun was pointed mostly away from Earth.⁹

How Scientists Study the Aurora Borealis

There are many reasons why scientists are interested in studying auroras. But how do they study this phenomenon? Canadian scientists are especially well-situated to conduct research on the Aurora Borealis, and they emerged as pioneers in the field by building and sending into space one of the world’s first artificial Earth satellites.²⁹ A variety of observation methods have been used to study the Aurora Borealis including:  detectors, satellites, and ground based methods.

Modern Observation Methods

Detectors

 All-Sky cameras

• capture movies of the entire sky which shows the movement of auroras¹⁰
• records the auroral substorm¹⁰
• led to discovery of fundamental features of the aurora, such as substorms and the auroral oval¹¹

 Spectrograph

• determines the wavelengths of light being emitted by the aurora²¹
• by measuring the Doppler shift in wavelength of a particle, scientists can derive its velocity¹¹

 Photometer

• measures the intensity of light¹¹

 Magnetometer

• measures changes in Earth’s magnetic field to help predict the onset of substorms²⁴

Satellites

• give a global view of the auroral oval¹⁴
• detect eruptions in the Sun to produce aurora forecasts¹⁴

Alouette

• The Alouette I, launched on September 29, 1962, was Canada’s first satellite, and it made Canada the fourth nation in the world to operate a satellite.³⁰ Canada’s entrance into the space age was a joint effort between scientists at the nation’s Defense and Research Telecommunications Establishment (DRTE) and America’s newly formed National Aeronautics and Space Administration (NASA).²⁹

Cassiope

• A Canadian satellite, launched on September 29, 2013, to study the effect of solar storms on radio communications, satellite navigation and other ground-based technologies.¹⁵

THEMIS mission

• Time History of Events and Microscale Interactions during Substorms¹²
• Five satellites were launched into space on February 17, 2007 to orbit Earth along the Earth’s magnetotail to capture the time history of solar storms and their resulting auroras.²⁰
• Studies substorms in the Earth’s magnetosphere which cause auroras to wildly shift in colour, size, and flutter, up to several times a day.^{12, 13}
• The most visible auroras occur during large magnetic storms.¹¹
• When the magnetosphere is overloaded with solar energy, it discharges a “storm” of electrons, which interact with particles in Earth’s upper atmosphere to produce auroras.¹²

Ground-Based Methods

SuperDARN Canada

• The Super Dual Auroral Radar Network (SuperDARN) is an international network of high-frequency (HF) radars located throughout the northern and southern hemispheres.  The purpose of the SuperDARN is to study plasma in the near-Earth space system, its interaction with the Earth’s atmosphere and geospace environment, its effects on the terrestrial “hard” infrastructure (e.g. communications, energy, transportation, etc…), and it’s role in the Sun-Earth system.  SuperDARN is operated and maintained by an international collaboration of multiple universities and research institutions, located throughout the world, including the University of Saskatchewan.²⁸ 

Weather balloons

• equipped with environment sensors and high definition cameras, released into the stratosphere²⁵
• use microphones to capture the sound of auroras, carry bacteria samples to capture the DNA-damaging effects of solar particles²⁵

Kjell Henriksen Observatory

• largest aurora observatory¹⁴
• situated under the northern polar cusp¹⁴

Terrella

• Kristian Olaf Birkeland (1867-1917), first to propose that auroras were caused by solar particles¹⁴
• built a simulation of Earth inside a glass box, complete with magnetic field, called Terralla, and successfully produced auroras¹⁴
• more recent Planeterralla, created by Guillaume Gronoff, of University of Leiceister, includes several spheres which show the difference between auroras on different planets, and better display how particles from the Sun follow magnetic field lines to the North and South poles¹⁶

Sounding rockets

• cost-effective ground based method¹⁷
• directly enter the aurora to measure its physical properties such as the auroral oval¹⁴

ICI-4 rocket

• launched by researchers from the University of Oslo from the Andøya Space Center in Norway, February 19, 2015¹⁸
• carrying 7 scientific instruments, intended to measure what happens when an electron cloud within the auroral oval collides with the aurora¹⁹
• 10 minute flight path, reaching 362 km in height¹⁹
• sought to better understand atmospheric events that disrupt navigation and communication systems, and to establish better weather prediction systems¹⁸

CaNoRock

• The Canada-Norway Student Sounding Rocket (CaNoRock) exchange program is a partnership between the University of Saskatchewan, the University of Alberta the University of Calgary, the University of Oslo, and the Andøya Rocket Range in Norway.  Undergraduate students spend a week on site at the Andøya Rocket Range, gaining hands-on experience at scientific rocket and payload instrument design.²⁶

 

References

¹N, Davis, The Aurora Watcher’s Handbook (University of Alaska Press, Fairbanks, AK, 1992), pp. 163-168.

²D. J. Ray, “Legends of the Northern Lights”, The Alaskan Sportsman, April 1958, reprinted in S. I. Akasofu, Alaska Geographic (6), 2 (1979).

³M. Nelson, Fifteen Native Tales about the Northern Light, (originally appearing in:  WWF July 27, 2014), WWW document, (http://goodnature.nathab.com/fifteen-native-tales-about-the-northern-lights/)

⁴Aurora, WWW document, (https://en.wikipedia.org/wiki/Aurora)

⁵S. Hearne, A Journey to the Northern Ocean: A journey from Prince of Wales’ Fort in Hudson’s Bay to the Northern Ocean in the years 1769, 1770, 1771, 1772 (The MacMillan Company of Canada, Toronto, Canada, 1958), pp. 221–222.

⁶Aurora Service, What is the Aurora Borealis, WWW document, (http://www.aurora-service.eu/aurora-school/aurora-borealis/).

⁷Aurora Service, All About the KP Index, WWW document, (http://www.aurora-service.eu/aurora-school/all-about-the-kp-index/).

⁸NASA, About Auroras, WWW document, (http://www.nasa.gov/mission_pages/SunEarth/news/gallery/aurora-index.html).

⁹M. Seeds, D. Backman, The Solar System, 9th ed. (Brooks Cole, Belmont, CA, 2015), pp. 163-164.

¹⁰H. Zell, NASA – The Mystery of Auroras, WWW document,  (http://www.nasa.gov/mission_pages/themis/auroras/aurora_feature.html).

¹¹Sandahl, In the Light of the Aurora: Optical Auroral Research in Northernmost Europe (Nordic Council of Ministers, Copenhagen, 2009), pp. 19-23. Retrieved from https://books.google.ca/books?id=bzKK61paVxUC&printsec=frontcover&dq=isbn:9289319003&hl=en&sa=X&ved=0ahUKEwjilPKnr8HKAhUiv4MKHUOSDcEQuwUIHzAA#v=onepage&q&f=false

¹²H. Zell, THEMIS Overview, WWW document, (http://www.nasa.gov/mission_pages/themis/mission/index.html).

¹³University of California Multiverse, Themis Discoveries, WWW document, (http://cse.ssl.berkeley.edu/artemis/mission-discoveries.html).

¹⁴H. Mason, Science of Northern Lights Aurora Borealis, WWW document, (http://www.Suntrek.org/blog/science-northern-lights-auroras-borealis).

¹⁵The Canadian Press, Canadian satellite to study nasty side of northern lights:

Cassiope satellite to study the effects of solar storms on Earth, September 29, 2013, WWW document, (http://www.cbc.ca/news/canada/canadian-satellite-to-study-nasty-side-of-northern-lights-1.1872599)

¹⁶E. Howell, Scientists Spark Auroras in a Bottle for Traveling Northern Lights Show, WWW document, (http://www.space.com/22594-aurora-bottle-northern-lights-show.html).

¹⁷The John Hopkins University Sounding Rocket Program, General Description of Sounding Rockets, WWW document, (http://www.pha.jhu.edu/groups/rocket/general.html).

¹⁸T. Borroz, Rocket Flown through Northern Lights to Help Unlock Space Weather Mysteries, WWW document, (http://www.gizmag.com/rocket-to-fly-through-northern-lights-to-help-predict-space-weather/36139/).

¹⁹L. Baddeley, UNIS Students Are ‘Go’ for Rocket Launch, WWW document, (http://www.unis.no/unis-students-are-go-for-rocket-launch/).

²⁰University of California Multiverse, Two Models, WWW document, (http://cse.ssl.berkeley.edu/artemis/mission-models.html).

²¹C. Landis, Studying the Aurora Australis from Antarctica, WWW document, (http://beyondpenguins.ehe.osu.edu/issue/polar-patterns-day-night-and-seasons/studying-the-aurora-australis-from-antarctica).

²²University of California Multiverse, Earth’s Magnetosphere, WWW document, (http://cse.ssl.berkeley.edu/artemis/mission-mag.html).

²³University of California Multiverse, Sun-Earth Connection, WWW document, (http://cse.ssl.berkeley.edu/artemis/mission-SunEarth.html).

²⁴H. Zell, THEMIS – Ground-Based Magnetometer (GMAG) Array, WWW document, (http://www.nasa.gov/mission_pages/themis/spacecraft/gmag.html).

²⁵C. Medred, Weather Balloons Launched into Alaska’s Aurora Borealis, WWW document,  (http://www.adn.com/video/weather-balloons-launched-alaskas-aurora-borealis).

²⁶Canada-Norway Student Rocket Program, CaNoRock, WWW document,

(http://physics.usask.ca/~kathryn/canorock/).

²⁷NASA, Magnetosphere, WWW document,

(http://ccmc.gsfc.nasa.gov/educational/MagnetosphereWebPage.php).

²⁸SuperDARN Canada, SuperDARN Canada: In the land of living skies, WWW document, (http://superdarn.usask.ca/).

²⁹http://www.asc-csa.gc.ca/eng/satellites/alouette.asp ³⁰http://www.ieee.ca/millennium/alouette/alouette_impact.html

³¹GPS World Staff, UNB Technology Launched into Space, WWW document, (http://gpsworld.com/unb-technology-launched-into-space/).

³² Scott Kelly (astronaut), WWW document, (https://en.wikipedia.org/wiki/Scott_Kelly_%28astronaut%29)

³³ North Magnetic Pole, WWW document, (https://en.wikipedia.org/wiki/North_Magnetic_Pole)

³⁴ South Magnetic Pole, WWW document, (https://en.wikipedia.org/wiki/South_Magnetic_Pole)

³⁵ Service Aurora, Aurora School, WWW document, (http://www.aurora-service.org/aurora-school/)

³⁶ Service Aurora, Aurora Forecast, WWW document, (http://www.aurora-service.org/aurora-forecast/)

³⁷ Nova PBS, Earth’s Magnetic Shield, WWW document, (https://www.youtube.com/watch?v=URN-XyZD2vQ&feature=youtu.be&t=1m6s)

³⁸ Solar Prominence, WWW document, (https://en.wikipedia.org/wiki/Solar_prominence)