aurora borealis
Polar (or aurora polaris) Aurora is a phenomenon as brightness or luminescence that appears in the night sky, now in polar regions, but can occur in other parts of the world for short periods.
The Northern Lights are visible from September to March, though at times makes its appearance over the course of months, as long as the atmospheric temperature is low enough.
and originate:
An aurora occurs when a solar mass ejection collides with the north and south of the Earth's magnetosphere, producing a diffuse but predominant projected light poles in the Earth's ionosphere.
That is the flow of particles called solar wind. The sun's surface or photosphere is about 6000 ° C
when the solar mass ejection collides with the planet admosfera
The solar wind particles traveling at speeds from 300 to 1000 km / s, so walking the Earth-Sun distance in about two days. In the vicinity of the Earth, the solar wind is deflected by the Earth's magnetic field or magnetosphere. The particles flow in the magnetosphere of the same way as a river around a stone or a pillar of a bridge.
colors and shapes.
Auroras are forms, structures and very different colors also change rapidly with time.Overnight, the aurora may begin as a very elongated bow isolated that is spreading on the horizon, generally east-west. Around midnight the arc can begin to increase their brightness.They begin to form waves or curls along the arc and vertical structures that look like rays of light very elongated and thin. Suddenly the whole sky can be filled with bands, spirals, and light rays tremble and move rapidly from horizon to horizon.
The activity can last from a few minutes to hours. As dawn approaches the whole process seems calm and only a few small areas of the sky appear bright until morning comes.
Although described a typical night lights, we can find multiple variations on the same theme.
The colors we see in the aurora depend on atomic or molecular species that solar wind particles excite and energy level that these atoms or molecules reach.
Oxygen is responsible for two primary colors of the aurora, green / yellow for a transition of energy 557.7 nm, while the red produces a less frequent 630.0 nm transition. To get an idea, our eye can see colors from violet in the spectrum would have a wavelength of about 390.0 nm to the red, about 750.0 nm.
Nitrogen, which a collision can start some of their outermost electrons, produces blue light, while Helium molecules are often responsible for the red / purple coloration of the lower edges of the auroras and the parties outermost curved.
The process is similar to what occurs in the neon tubes of ads or television tubes. In a neon tube, the gas is excited by electrical currents and de-energized the typical light pink crosses we all know. In a television screen an electron beam controlled by electric and magnetic fields incident on the same, making it glow in various colors depending on the phosphorescent chemical coating products on the inside of the screen.
