50 Fun Facts About Aurora

What causes an aurora?

The collisions excite oxygen and nitrogen, which then emit green, red and purple light.

What is the aurora in the Antarctic called?

Its features are almost identical to the northern lights and it changes in step with them.

The word 'aurora' comes from the Roman goddess of what?

Borealis and australis come from Boreas and Auster, the Greco-Roman gods of the north and south winds.

Who used the term 'aurora borealis' in 1619, before Gassendi's 1649 description made it stick?

The term entered the English language in 1828.

Which colour of aurora is the most common?

It is emitted at 557.7 nm at altitudes where collisions are frequent and human eyes are most sensitive.

Red auroral light at the highest altitudes is emitted by which excited species?

The 630 nm red line needs low particle density, because the excited atom can take up to two minutes to emit.

Blue and purple auroral emissions at the lower edges of the curtains come from what?

The dominant blue line is at 428 nm, and these fringes appear at the highest levels of solar activity.

Auroras are most commonly seen in a band centred on roughly which latitude, north and south?

The 'auroral zone' is about 6 degrees wide, and the lit region is pushed away from the geomagnetic pole.

What is the region currently displaying an aurora called?

It sits about 15 degrees from the geomagnetic pole on the noon side and 23 degrees on the midnight side.

Carl Stormer's triangulation of 12,000+ auroras found their heights peaked at around what altitude?

None was below 70 km and only 6.5% were above 150 km.

Which of these is one of the five main auroral forms seen from the ground, according to Clark (2007)?

The list runs from a mild glow through patches, arcs and rays to coronas that diverge from one point in the sky.

Discrete auroras can be bright enough to do what at night?

Arcs can fragment into rapidly changing rayed features that fill the whole sky.

Large geomagnetic storms that push auroras to lower latitudes are most common around the peak of what?

They stay frequent for about three years after the peak, when coronal mass ejections intensify the flow of particles from the Sun.

Which 1859 event, the greatest geomagnetic storm on record, brought auroras to the tropics?

Balfour Stewart at Kew Observatory linked the storm to Richard Carrington's white-light solar flare of 1 September.

During the 1859 storm, telegraph operators between Boston and which city ran on aurora current alone?

They disconnected their batteries and found the signal came through better than before.

A 1770 Japanese diary found in 2017 depicted auroras over which ancient capital?

In 620 AD, 'red pheasant tails' seen over Japan may likewise have been a red aurora.

In May 2024, solar storms made the aurora borealis visible as far south as Ferdows, in which country?

On rare occasions the northern lights reach the Mediterranean and the southern United States.

What does the citizen-science acronym STEVE stand for?

STEVE is not technically an aurora but a 25 km wide ribbon of 3,000 C plasma flowing at 6 km/s.

Citizen scientists from which country discovered the 'dune aurora', first reported in 2020?

The regularly spaced stripes are thought to be caused by an atmospheric wave modulating oxygen density.

Which aurora type is caused by positive particles and is too dim for the naked eye?

The proton grabs an electron and the resulting hydrogen atom emits the light.

Pulsating auroras flicker with periods of roughly how long?

They come with lower emission heights and above-average speeds of the Sun's particle flow, around 500 km/s.

Auroral kilometric radiation, discovered in 1972, is a strong radio emission at around what frequency?

Ionospheric absorption means it can only be observed from space.

What is the flow of magnetised hot plasma from the Sun that ultimately powers auroras called?

It reaches Earth at about 400 km/s and much faster during magnetic storms.

Energy transfers most effectively from the Sun's plasma flow to Earth's magnetosphere when the interplanetary magnetic field points which way?

That lets its field lines connect with Earth's through magnetic reconnection.

Which Norwegian scientist developed a foundational theory of geomagnetism and auroras around 1900?

The field-aligned electric currents that feed bright auroras are named Birkeland currents after him.

Which two Swedes in Uppsala linked compass-needle fluctuations to an overhead aurora in 1741?

It supported their theory that 'magnetic storms' were behind the wobbling compasses.

Benjamin Franklin's 1778 paper suggested auroras were caused by what?

He imagined the charge, intensified by snow and moisture, breaking through the low atmosphere and running toward the equator.

Which mission's probes first pinned down the trigger of a magnetospheric substorm in February 2008?

Two of the five probes, about a third of the way to the Moon, caught the magnetic reconnection event.

Jupiter's main auroral ring is associated with plasma produced by which moon?

Io's volcanism and ionosphere make it a powerful aurora source; auroras have even been seen over Io, Europa and Ganymede themselves.

Why do Venusian auroras appear as diffuse patches sometimes covering the whole disc?

Electrons from the Sun simply hit the night-side atmosphere wherever they arrive.

Which orbiter's SPICAM instrument detected an aurora on the red planet on 14 August 2004?

It appeared over Terra Cimmeria, where the crustal magnetic field is strongest.

On which planet do X-ray auroras occur on the surface rather than in an atmosphere?

Its exosphere is so thin that the emissions, seen by Mariner 10 and MESSENGER, happen on the ground.

Cometary auroras were observed between 2014 and 2016 on comet 67P by which spacecraft?

They showed up in far-ultraviolet light, spread diffusely around a comet with no magnetic field.

The first extra-solar auroras, found in 2015, were how much brighter than the northern lights?

They glowed mainly red over the brown dwarf LSR J1835+3259.

The earliest datable record of an aurora, from 977 or 957 BC, appears in which Chinese chronicle?

A Chinese legend from around 2600 BC may describe an even older wintertime aurora.

Which Roman writer described a red aurora over Ostia so intense a fire cohort galloped to help?

In his Naturales Quaestiones he classified auroras as barrel-like, chasms, bearded and cypress-shaped.

The 1230 Norwegian chronicle Konungs Skuggsja gave three causes for the northern lights. Which was one?

The other guesses were vast fires around the ocean and sun flares reaching round to Earth's night side.

What did the Gunditjmara people of western Victoria call the aurora australis?

Many Aboriginal Australian traditions link the southern lights with fire; the Dieri saw an evil spirit lighting a great blaze.

To the Maori, the aurora australis, Tahunui-a-rangi, meant what?

They were said to be lit by ancestors who had sailed south to a land of ice.

In Sami mythology, the northern lights were said to be what?

Many northern peoples of Eurasia and North America share the belief that the lights are the blood of the deceased.

The Chipewyan Dene told Samuel Hearne the aurora was like sparks from which animal's fur?

They believed the lights were the spirits of departed friends dancing happily in the sky.

After which Civil War battle did Confederates take an aurora as a sign God was with them?

Frederic Edwin Church's painting Aurora Borealis is often read as a comment on the war.

Auroras were rare between about 1645 and 1715, a period matching what?

Halley said that before 1716 nothing of the kind had been recorded for more than 80 years.

In Service's 'The Ballad of the Northern Lights', a prospector decides the aurora is the glow from what?

He stakes his claim and heads to town to find investors.

Who delivers the 'localized entirely within your kitchen?' line to Principal Skinner in The Simpsons?

The exchange resurfaces as a meme every time the northern lights are photographed somewhere unexpected.

Tycho Brahe recommended sulphur to cure diseases he blamed on what?

Walter William Bryant recorded the claim in his 1920 book on Kepler.

The 'borealis' in aurora borealis comes from Boreas, the Greco-Roman god of what?

Its southern twin, aurora australis, takes its name from Auster, the south wind.

The green light that dominates most auroras is emitted by atomic oxygen at what wavelength?

Higher up, where collisions are rarer, oxygen instead glows red at 630 nm; that transition can take up to two minutes to fire.

What term describes mirror-image displays in both hemispheres on the same magnetic field lines?

Aircraft flying from Alaska and New Zealand tried to photograph both halves at once in 1967, 1968, 1970 and 1971, with some success.

Which American published nine papers collecting worldwide reports of the 1859 auroral storm?

Loomis's 1860 work, followed by Fritz and Tromholt in 1881, established that auroras appear mainly in a distinct auroral zone.