Boston University Center for Space Physics
An image of red light taken from Italy in 2011.
Officially known in the Northern hemisphere as the aurora borealis, the Northern Lights are natural phenomena featuring beautifully colored light displays over the Earth. Above is a photograph of an aurora taken on from the International Space Station on Sept 2, 2014. "This is what we see looking down while being inside an #aurora," wrote German astronautAlexander Gerst.
VIDEO: Auroras Are So Pretty! Lets Shoot Them!
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In 1621, a French scientist, Pierre Gassendi, saw the lights in the north and named after the Roman goddess of dawn, Aurora. He added the word "borealis" for the Roman god of the north wind, Boreas. In the southern hemisphere, they are called aurora australis, meaning "southern." The lights are usually seen after dusk near both poles. Although they look elegant and calm, aurorae are produced from millions of explosions of magnetic energy.BLOG: Space Station Astronauts Log One Million Photos
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These haunting lights are a form of intense space weather, a result of the atmosphere shielding the Earth against fierce solar particles that would otherwise make our planet uninhabitable. Millions and millions of electrically charged particles in the solar wind wash over Earth and smash into upper atmospheric gases. The energy from each collision is released as photons -- particles of light. This causes the particles to glow. Aurorae are typically seen at the poles because Earth's magnetic field syphons them around the planet. Think of water moving around a rock protruding the surface of a river.NEWS: Faint 'Red Arcs' Spotted Over Europe
The lights are the most frequent between September and October (autumn) and then occur again between March and April (spring) because of Earth's tilt in relation to the sun. They are also visible sometimes in the winter. When darkness overtakes the sky, the lights stand out even brighter and can be seen longer.Dazzling Aurora Appears Over Antarctica: Big Pic
NASA/Goddard Space Flight Center Scientific V
Tasked with measuring aurora, NASA's THEMIS team has 20 ground-based observatories (GBOs) across Alaska and Canada. Each station includes a digital camera with a fish-eye lens to capture images of the aurora every three seconds and a magnetometer to measure changes in Earth's magnetic field due to electric currents surging through the upper atmosphere. This visualization shows the ground station locations' radial coverage. Each blue circle represents a circular distance of 540 kilometers (335 miles).BLOG: Lightning, Stars, And Aurorae Shine In Epic Time-Lapse
The shape of the aurorae can vary widely. They can appear in a dull glow, arcs, swirls or streaks across the sky called "curtains" that always run east-west, moving and changing constantly. Their "shimmering" effect is actually producing by fading particle explosions just as new ones occur. Although harmless to life on Earth, the aurora can cause power disruptions in satellite communications and in radio and television broadcasts.
NASA/JPL, Phillippe Bourseiller/Getty Images
The higher in the sky these collisions occur, the more intense the color of the lights. Most aurorae occur about 60 to 620 miles above the earth's surface. They're most commonly green. Only displays extremely high in the upper atmosphere will turn red or purple. Atmospheric gases -- hydrogen, nitrogen, oxygen -- interacting with the solar particles also play a role in the manner in which the colorful display appears.NEWS: Stunning Northern Lights Over Maine Lake
NASA/Goddard, Ron Crabtree/Getty Images
During peaks in the solar cycle, when solar flares produce the most intense spurts of wind from the sun, more particles collide with Earth's atmosphere causing more brilliant aurorae. These vibrant green aurorae, shown here above the Alaskan wilderness, are the most dominant aurora color. They occur from about 100 kilometers (about 62 miles) to 250 kilometers (about 155 miles) above the Earth's surface and are caused by the reaction of solar particles with oxygen in the atmosphere.PHOTOS: Spectacular Displays of Dancing Aurora
NASA, Michael Medford/Getty Images
Blue aurorae are found at the lowest parts of the atmosphere, around 60 miles above the Earth's surface. They are produced from collisions with molecular nitrogen.PHOTOS: Stunning Auroras Seen Over Swedish Mountains
NASA, Tom Walker/Getty Images
During magnetic solar storms, aurorae may shift from the polar regions toward the equator because eruptions from the sun interfere with Earth's magnetic field. When this happens, residents as far as the Dakotas can see intense Northern Lights such as the ones pictured here.VIDEO: Solar Storms: 5 Reasons to Care Right Now
NASA scientists are on an endless search to find Earth-like features off our planet, and Saturn's aurorae fit the bill. The aurorae on Saturn are generated from charged particles released by the sun interacting with Saturn's upper atmosphere, causing them to glow. Using invisible light, Cassini cameras were able to capture aurorae at Saturn's poles for the first time in 2008. The aurorae appear at the poles because the ringed planet's magnetic field forces them pole-ward, exactly what happens on Earth.BLOG: 'Failed Stars' May Shine With Alien Aurorae
John T. Clarke (U. Michigan), ESA, NASA
Jupiter is no different. The gas giant also showcases aurora at its poles for the same reasons they appear on Saturn and Earth. However, unlike Earth, Jupiter's aurora include several bright streaks and dots, instead of a more uniform "curtain" pattern. Magnetic fields connecting Jupiter to its largest moons -- specifically Io, Ganymede and Europa -- are to blame.VIDEO: Massive Northern And Southern Lights Explained
Glowing red arcs invisible to the naked eye have now been detected high above most of Europe using advanced cameras pointed at the sky.
When streams of high-energy, charged particles come rushing from the sun to batter Earth, they cause what are called geomagnetic storms. These events are disruptions in the magnetosphere, the part of Earth's atmosphere dominated by the planet's magnetic field. The most dramatic effects of these storms are giant, bright auroras in Earth's polar regions, but the tempests result in other striking consequences as well, such as faintly glowing red arcs high up in the ionosphere. This is the electrically charged part of Earth's atmosphere, stretching from about 50 to 370 miles (85 to 600 kilometers) above the Earth.
The arcs give off a very specific wavelength of red light, but are too faint to see with the naked eye. They appear at lower latitudes, unlike auroras, which typically occur over higher latitudes.
Scientists had thought there was too much light pollution over Europe for the dim, red arcs to be visible. But now, the new All-Sky Imaging Air-Glow Observatory (ASIAGO), located in northern Italy, is using cameras with highly sensitive sensors and a fish-eye lens to observe these red arcs and faint auroral activity over most of the continent. (Image Gallery: Amazing Auroras)
An international team of scientists watched the sky with the observatory during a geomagnetic storm that struck Earth in 2011. After comparing their observations with satellite- and ground-based observations, the researchers found that red arcs could reach all the way down to Europe, stretching from Ireland in the west to Belarus in the east.
The fact that scientists can now see these arcs over Europe means that, in combination with similar data from the Americas and the Pacific Ocean, researchers can now see how long the arcs stretch across vast distances over the planet "and thus how long it takes the magnetosphere to be drained of its storm-time energy," researcher Michael Mendillo, a space physicist at Boston University, told OurAmazingPlanet. (Red arcs happen when oxygen atoms in the ionosphere emit light, after being excited by electrons heated at greater heights in Earth's magnetosphere.)
Such data could in turn help scientists analyze the effects of space activity on radio communications in real time and support projects aiming to model space weather, researchers added.
The scientists detailed their findings online Feb. 25 in the journal Space Weather.
More from LiveScience:
Strange & Shining: Gallery of Mysterious Night Lights
Aurora Guide: How the Northern Lights Work (Infographic)
Video - Over Earth: Aurora Night Pass Above America
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