what are northern lights caused by?

Answer 1

I was going to try and explain it in my own words but I am not sure if I could have explained it as well


Auroral mechanism
The aurora is now known to be caused by electrons of typical energy of 1-15 keV, i.e. the energy obtained by the electrons passing through a voltage difference of 1,000-15,000 volts. The light is produced when they collide with atoms of the upper atmosphere, typically at altitudes of 80-150 km. It tends to be dominated by emissions of atomic oxygen--the greenish line at 557.7 nm and (especially with electrons of lower energy and higher altitude) the dark-red line at 630.0 nm. Both these represent forbidden transitions of atomic oxygen from energy levels which (in absence of collisions) persist for a long time, accounting for the slow brightening and fading (0.5-1 sec) of auroral rays. Many other lines can also be observed, especially those of molecular nitrogen, and these vary much faster, revealing the true dynamic nature of the aurora.

Auroras can also be observed in the ultra-violet (UV) light, a very good way of observing it from space (but not from ground--the atmosphere absorbs UV). The Polar spacecraft even observed it in X-rays. The image is very rough, but precipitation of high-energy electrons can be identified.

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Auroral forms and magnetism

A coronaTypically the aurora appears either as a diffuse glow or as "curtains" that approximately extend in the east-west direction. At some times, they form "quiet arcs", at others ("active aurora") they evolve and change constantly. Each curtain consists of many parallel rays, each lined up with the local direction of the magnetic field lines, suggesting that aurora is shaped by the Earth's magnetic field, Indeed, satellites show auroral electrons to be guided by magnetic field lines, spiraling around them while moving earthwards.

The curtains often show folds called "striations". When the field line guiding a bright auroral patch leads to a point directly above the observer, the aurora may appear as a "corona" of diverging rays, an effect of perspective.

In 1741, Hiorter and Celsius first noticed other evidence for magnetic control, namely, large magnetic fluctuations occurred whenever the aurora was observed overhead. This indicates (it was later realized) that large electric currents were associated with the aurora, flowing in the region where auroral light originated. Kristian Birkeland (1908)[1] deduced that the currents flowed in the east-west directions along the auroral arc, and such currents, flowing from the dayside towards (approximately) midnight were later named "auroral electrojets" (see also Birkeland currents).

Still more evidence for a magnetic connection are the statistics of auroral observations. Elias Loomis (1860) and later in more detail Hermann Fritz (1881)[2] established that the aurora appeared mainly in the "auroral zone", a ring-shaped region of approx. radius 2500 km around the magnetic pole of the Earth, not its geographic one. It was hardly ever seen near that pole itself. The instantaneous distribution of auroras ("auroral oval", Yasha [or Yakov] Felds[h]tein 1963[3]) is slightly different, centered about 3-5 degrees nightward of the magnetic pole, so that auroral arcs reach furthest equatorward around midnight.


Aurora australis[edit]
The solar wind and magnetosphere

Schematic of Earth's magnetosphereThe Earth is constantly immersed in the solar wind, a rarefied flow of hot plasma (gas of free electrons and positive ions) emitted by the sun in all directions, a result of the million-degree heat of the sun's outermost layer, the solar corona. The solar wind usually reaches Earth with a velocity around 400 km/s, density around 5 ions/cc and magnetic field intensity around 2–5 nT (nanoteslas; the Earth's surface field is typically 30,000–50,000 nT). These are typical values. During magnetic storms, in particular, flows can be several times faster; the interplanetary magnetic field (IMF) may also be much stronger.

The IMF originates on the sun, related to the field of sunspots, and its field lines (lines of force) are dragged out by the solar wind. That alone would tend to line them up in the sun-earth direction, but the rotation of the Sun skews them (at Earth) by about 45 degrees, so that field lines passing Earth may actually start near the western edge ("limb") of the visible sun.

The Earth's magnetosphere is the space region dominated by its magnetic field. It forms an obstacle in the path of the solar wind, causing it to be diverted around it, at a distance of about 70,000 km (before it reaches that boundary, typically 12,000–15,000 km upstream, a bow shock forms). The width of the magnetospheric obstacle, abreast of Earth is typically 190,000 km, and on the night side a long "magnetotail" of stretched field lines extends to great distances.

The ultimate energy source of the aurora is undoubtedly the solar wind flowing past the Earth.

Both the magnetosphere and the solar wind consist of plasma, which can conduct electricity. It is well known (since Faraday's work around 1830) that if two electric conductors are immersed in a magnetic field and one moves relative to the other, while a closed electric circuit exists which threads both conductors, then an electric current will arise in that circuit. Electric generators of dynamos make use of this process ("the dynamo effect"), but the conductors can also be plasmas or other fluids.

Answer 2

The sun gives off high-energy charged particles (also called ions) that travel out into space at speeds of 300 to 1200 kilometres per second. A cloud of such particles is called a plasma. The stream of plasma coming from the sun is known as the solar wind. As the solar wind interacts with the edge of the earth's magnetic field, some of the particles are trapped by it and they follow the lines of magnetic force down into the ionosphere, the section of the earth's atmosphere that extends from about 60 to 600 kilometres above the earth's surface. When the particles collide with the gases in the ionosphere they start to glow, producing the spectacle that we know as the auroras, northern and southern. The array of colours consists of red, green, blue and violet.

Click here to see some pictures http://virtual.finland.fi/finfo/english/aurora_borealis2.html

Answer 3

Northern lights are caused by ionizing radiation hitting atoms in the atmosphere.

The high-energy radiation comes from the Sun (solar wind). When it hits oxygen and nitrogen atoms, it temporarily removes an electron from the outer shells of these atoms.

After a while this electron joins the atom again. When this happens, a specific amount of energy is released in the form of visible radiation. Because the amount of energy only depends on the type of atom, it comes in specific frequencies/colors -- red for oxygen, green for nitrogen.

Answer 4

Cold Environments

Answer 5

When I first moved to Alaska I was amazed by them. Other people have beat me to the explanation and they are correct. Words cannot describe the beauty of them. I could actually feel the energy from the lights one time when they were directly overhead of me. It was an incredible experience.

Answer 6

considering Earth's magnetic fields are weaker on the poles, photo voltaic radiation quite enters our ecosystem there. even as it does, it burns up, ensuing contained in the colourful lighting fixtures fixtures we've all come to attraction to close and love.

Answer 7

by gamma from the sun tha is block for the magnetic field of the earth

Answer 8

sun and moon light refracting through the atmosphere