NordenBladet – An aurora (plural: auroras or aurorae), sometimes referred to as polar lights, northern lights (aurora borealis) or southern lights (aurora australis), is a natural light display in the Earth’s sky, predominantly seen in the high-latitude regions (around the Arctic and Antarctic).
Auroras are produced when the magnetosphere is sufficiently disturbed by the solar wind that the trajectories of charged particles in both solar wind and magnetospheric plasma, mainly in the form of electrons and protons, precipitate them into the upper atmosphere (thermosphere/exosphere) due to Earth’s magnetic field, where their energy is lost.
The resulting ionization and excitation of atmospheric constituents emits light of varying color and complexity. The form of the aurora, occurring within bands around both polar regions, is also dependent on the amount of acceleration imparted to the precipitating particles. Precipitating protons generally produce optical emissions as incident hydrogen atoms after gaining electrons from the atmosphere. Proton auroras are usually observed at lower latitudes.
Etymology
The word “aurora” comes from the Latin word for “dawn, morning light”, since auroras were formerly thought to be the first light of dawn.
Occurrence of terrestrial auroras
Most auroras occur in a band known as the “auroral zone”, which is typically 3° to 6° wide in latitude and between 10° and 20° from the geomagnetic poles at all local times (or longitudes), most clearly seen at night against a dark sky. A region that currently displays an aurora is called the “auroral oval”, a band displaced towards the night side of the Earth. Early evidence for a geomagnetic connection comes from the statistics of auroral observations. Elias Loomis (1860), and later Hermann Fritz (1881) and S. Tromholt (1882) in more detail, established that the aurora appeared mainly in the auroral zone. Day-to-day positions of the auroral ovals are posted on the Internet.
In northern latitudes, the effect is known as the aurora borealis or the northern lights. The former term was coined by Galileo in 1619, from the Roman goddess of the dawn and the Greek name for the north wind. The southern counterpart, the aurora australis or the southern lights, has features almost identical to the aurora borealis and changes simultaneously with changes in the northern auroral zone. The Aurora Australis is visible from high southern latitudes in Antarctica, Chile, Argentina, New Zealand, and Australia.
A geomagnetic storm causes the auroral ovals (north and south) to expand, and bring the aurora to lower latitudes. The instantaneous distribution of auroras (“auroral oval”) is slightly different, being centered about 3–5° nightward of the magnetic pole, so that auroral arcs reach furthest toward the equator when the magnetic pole in question is in between the observer and the Sun. The aurora can be seen best at this time, which is called magnetic midnight.
Auroras seen within the auroral oval may be directly overhead, but from farther away, they illuminate the poleward horizon as a greenish glow, or sometimes a faint red, as if the Sun were rising from an unusual direction. Auroras also occur pole ward of the auroral zone as either diffuse patches or arcs, which can be sub visual.
Auroras are occasionally seen in latitudes below the auroral zone, when a geomagnetic storm temporarily enlarges the auroral oval. Large geomagnetic storms are most common during the peak of the 11-year sunspot cycle or during the three years after the peak. An aurora may appear overhead as a “corona” of rays, radiating from a distant and apparent central location, which results from perspective. An electron spirals (gyrates) about a field line at an angle that is determined by its velocity vectors, parallel and perpendicular, respectively, to the local geomagnetic field vector B. This angle is known as the “pitch angle” of the particle. The distance, or radius, of the electron from the field line at any time is known as its Larmor radius. The pitch angle increases as the electron travels to a region of greater field strength nearer to the atmosphere. Thus, it is possible for some particles to return, or mirror, if the angle becomes 90° before entering the atmosphere to collide with the denser molecules there. Other particles that do not mirror enter the atmosphere and contribute to the auroral display over a range of altitudes. Other types of auroras have been observed from space, e.g.”poleward arcs” stretching sunward across the polar cap, the related “theta aurora”, and “dayside arcs” near noon. These are relatively infrequent and poorly understood. Other interesting effects occur such as flickering aurora, “black aurora” and subvisual red arcs. In addition to all these, a weak glow (often deep red) observed around the two polar cusps, the field lines separating the ones that close through the Earth from those that are swept into the tail and close remotely.
Aurora borealis. Each appearance of the northern lights is unique. Often you see three green bands across the night sky. Or the lights come as flickering curtains or rolling smoke. The color is a luminous green, often with a hint of pink along the edge, and occasionally with a deep violet centre. If there is a lot of activity up there, the northern lights explode for a minute or two in a corona. (Photos: NordenBladet)
The science behind the northern lights
What exactly is the northern lights? It is the sun that lies behind the formation of the auroras.During large solar explosions and flares, huge quantities of particles are thrown out ofthe sun and into deep space. When the particles meet the Earth’s magnetic shield, they areled towards a circle around the magnetic North Pole, where they interact with the upper layers of the atmosphere. The energy which is then released is the northern lights. All this happens approximately 100 kilometres above our heads.
Living legend
Perhaps not so surprisingly, the northern lights’ spectacle has given rise to as many legends as there have been people watching. Symbols linked to the northern lights are found on the Sami shamanistic drum. The phenomenon has several different names in Sami. It is, for instance, known as Guovssahas, which means “the light which can be heard”. The northern lights were traditionally associated with sound by the Sami, the indigenous people of Norway. And during the Viking Age (793–1066 AD), the northern lights were said to be the armour of the Valkyrie warrior virgins, shedding a strange flickering light.
Be patient
When dreaming about seeing the northern lights, you must remember that you are at the complete mercy of nature. The northern lights love to play hide and seek. Observing the Aurora borealis is often a tug of war between your patience and the aurora itself. Stay in the northern lights area at least a week, preferably two, and you will be rewarded – unless local weather suddenly decides to obstruct your view with clouds.
https://www.youtube.com/watch?v=iQ3BQ3xRTzE
Aurora Borealis and Northern Lights FAQs:
1. Do the Northern Lights really exist?
The bright dancing lights of the aurora are actually collisions between electrically charged particles from the sun that enter the earth’s atmosphere. The lights are seen above the magnetic poles of the northern and southern hemispheres.
2. What is the best time of year to see the northern lights?
In this period of time, no Northern Lights can be observed. In the most intense Northern Lights area (notably Alaska, Iceland, Northern Scandinavia and Yukon), the lights are observed from late August to mid April. However, from late September to late March, it is dark after 6pm, and one enjoys maximum chances.
3. Can you see northern lights with naked eyes?
The Aurora Borealis appears in a spectrum of colors. … Our naked eye can most easily see the green-yellow part of the spectrum where the sun emits most of its light. Green is the most common color observed but the Northern Lights can also appear white-gray.
4. Are the Northern Lights dangerous?
The Northern Lights occur so high up in the atmosphere that they don’t pose any threat to people watching them from the ground. The aurora itself is not harmful to humans but the electrically charged particles produced could have some potentially negative effects to infrastructure and technology.
5. Do the Northern Lights give off radiation?
“Northern Lights appear when high energy particles from the sun collide with atoms and molecules in the atmosphere, causing them to emit light. … And no, the Northern Lights themselves are no source of radiation but a manifestation of what is happening all the time (the sun emits energy).
6. Can you see northern lights if cloudy?
The best conditions for seeing the Northern Lights include a few key factors: Mainly dark skies without any clouds. And, usually, the less light pollution in the sky, the better. … While it’s true that a full moon can dim the Lights a bit, it certainly doesn’t negate your chances of seeing them.
7. How often do the northern lights occur?
April to August. To see the Northern Lights you need dark skies and from early-April until late-August, the Aurora may be blazing across the Arctic firmament but it is visible only to scientific equipment, as the skies are just too light for the human eye to see the show.
8. When can I see northern lights in Norway? Can northern lights be seen in Norway?
The northern lights are therefore always present. Historically, the chances of seeing the northern lights are best viewed in Northern Norway between October and March, because the polar night makes them easier to see. The northern lights are visible in a belt around the magnetic North Pole.
9. Where is the best place to see northern lights Norway?
Tromsø Tromso is “the capital of the Arctic”, and it’s location 217 miles north of the Arctic Circle makes it one of the best places on earth to observe the northern lights. This is the largest city in Northern Norway, and operates as a hub for Safaris and nightly visits to northern light camps.
10. What month is best to see the northern lights in Norway?
The weather in November, December and January can be brutal, so a lot of people say that the best months to see the Northern Lights in Norway are late September, October, February, and March.
11. Can you see Northern Lights from Oslo?
Of course, if the conditions are right, there’s nothing to stop you catching the lights well outside that area. It’s not unheard of to see them as far north as Svalbard or as far south as Oslo – but realistically, the chances of you seeing green skies over the Norwegian capital are very low indeed.
12. Can you see the Northern Lights from the Norwegian fjords?
The Northern Lights are visible between October and March when the sky is clear, depending on the Northern Lights activity. The best place to see the Northern Lights is in the Northern, Arctic parts of Norway.
13. Can you see Northern Lights from Reykjavik?
Can You See The Northern Lights in Reykjavik? … You may be able to see the Northern Lights in the city but a few criteria would have to be met. You will need darkness and clear skies and northern light activity, all three of which only appear together mostly during the winter months.
14. Do the Northern Lights happen every night?
The Northern Lights are unpredictable. In order to see the Northern Lights, you need a dark, clear night. There also needs to be solar flares on the sun or solar wind; the Aurora Borealis happens when particles from the sun enter Earth’s atmosphere and collide violently with gas atoms.
15. Is it a good night to see the northern lights?
The Best Time of Day. First and foremost, to see the Northern Lights, the skies must be dark. Once darkness falls, the Aurora can be visible at any time of day and we have seen them as early as 4pm and as late as 6am (that was quite a night!).
16. What is the auroral oval?
When we look up and see the Northern Lights, we are only seeing a tiny section of a huge auroral oval. The geomagnetic field surrounds the Earth and extends into space as the magnetosphere, and the Geomagnetic Pole is the centre of the region around which the Northern Lights can be seen.
17. What is the auroral zone?
The auroral zone is a ring of light emission created by the precipitation of particles in the atmosphere and centred around the magnetic pole. The cusp and boundary layers on the dayside, and the plasma sheet and plasma sheet boundary layer on the nightside are the sources of these precipitations.
18. Why is it called aurora borealis?
In northern latitudes, the effect is known as the aurora borealis or the northern lights. The former term was coined by Galileo in 1619, from the Roman goddess of the dawn and the Greek name for the north wind. … The aurora can be seen best at this time, which is called magnetic midnight.
https://www.instagram.com/p/BpT4BtcHImX/
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