Aurora!!

      Assalamualaikum and hi to all of you!! It's a long time since i have updated this blog.. Today i want to post about something unique and beautiful! It's AURORA.. Weird name huh?:D The reason i post about aurora it's because i like it and it's rarely happen!
      For futher information read this->    An aurora (plural: aurorae or auroras) is a natural light display in the sky particularly in the high latitude (Arctic and Antarctic) regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere (thermosphere). The charged particles originate in the magnetosphere and solar wind and, on Earth, are directed by the Earth's magnetic field into the atmosphere.          Aurora is classified as diffuse or discrete aurora. Most aurorae occur in a band known as the auroral zone which is typically 3° to 6° in latitudinal extent and at all local times or longitudes. The auroral zone is typically 10° to 20° from the magnetic pole defined by the axis of the Earth's magnetic dipole.
During a geomagnetic storm, the auroral zone will expand to lower latitudes. The diffuse aurora is a featureless glow in the sky which may not be visible to the naked eye even on a dark night and defines the extent of the auroral zone. The discrete aurora are sharply defined features within the diffuse aurora which vary in brightness from just barely visible to the naked eye to bright enough to read a newspaper at night. Discrete aurorae are usually observed only in the night sky because they are not as bright as the sunlit sky. Aurorae occur occasionally poleward of the auroral zone as diffuse patches or arcs (polar cap arcs) which are generally invisible to the naked eye.
In northern latitudes, the effect is known as the aurora borealis (or the northern lights), named after the Roman goddess of dawn, Aurora, and the Greek name for the north wind, Boreas, by Pierre Gassendi in 1621. Auroras seen near the magnetic pole may be high overhead, but from farther away, they illuminate the northern horizon as a greenish glow or sometimes a faint red, as if the Sun were rising from an unusual direction. Discrete aurorae often display magnetic field lines or curtain-like structures, and can change within seconds or glow unchanging for hours, most often in fluorescent green. The aurora borealis most often occurs near the equinoctes. The northern lights have had a number of names throughout history. The Cree call this phenomenon the "Dance of the Spirits". In Europe, in the Middle Ages, the auroras were commonly believed a sign from God.
Its southern counterpart, the aurora australis (or the southern lights), has almost identical features to the aurora borealis and changes simultaneously with changes in the northern auroral zone and is visible from high southern latitudes in Antarctica, South America, New Zealand and Australia.( be sure to watch it live from there!)
Aurorae occur on other planets. Similar to the Earth's aurora, they are visible close to the planet's magnetic poles.
Modern style guides recommend that the names of meteorological phenomena, such as aurora borealis, be uncapitalized.

Some pictures of AURORA!

                                                    SubhanALLAH!! It's really gorgeous!

                                    This picture is taken at the outer space using the satellite! Beautiful!
Aurora's frequency of occurrence.,.,.
      Auroras are occasionally seen in temperate latitudes, when a magnetic storm temporarily enlarges the auroral oval. Large magnetic storms are most common during the peak of the eleven-year sunspot cycle or during the three years after that peak.(Oh my God! will i ever get to see this?) However, within the auroral zone the likelihood of an aurora occurring depends mostly on the slant of interplanetary magnetic field (IMF) lines (the slant is known as B_z), being greater with southward slants.

Geomagnetic storms that ignite auroras actually happen more often during the months around the equinoctes. It is not well understood why geomagnetic storms are tied to Earth's seasons while polar activity is not. But it is known that during spring and autumn, the interplanetary magnetic field and that of Earth link up. At themagnetopause, Earth's magnetic field points north. When B_z becomes large and negative (i.e., the IMF tilts south), it can partially cancel Earth's magnetic field at the point of contact. South-pointing B_z's open a door through which energy from the solar wind can reach Earth's inner magnetosphere.

The peaking of B_z during this time is a result of geometry. The IMF comes from the Sun and is carried outward with the solar wind. The rotation of the Sun causes the IMF to have a spiral shape called the Parker spiral. The southward (and northward) excursions of B_z are greatest during April and October, when Earth's magnetic dipole axis is most closely aligned with the Parker spiral.

However, B_z is not the only influence on geomagnetic activity. The Sun's rotation axis is tilted 8 degrees with respect to the plane of Earth's orbit. The solar wind blows more rapidly from the Sun's poles than from its equator, thus the average speed of particles buffeting Earth's magnetosphere waxes and wanes every six months. The solar wind speed is greatest – by about 50 km/s, on average – around 5 September and 5 March when Earth lies at its highest heliographic latitude.

Still, neither B_z nor the solar wind can fully explain the seasonal behavior of geomagnetic storms. Those factors together contribute only about one-third of the observed semiannual variations.

posted by, aiNa..
thanks to, http://en.wikipedia.org/wiki/Aurora_(astronomy)
&http://www.google.com.my/search?q=aurora&hl=en&prmd=imvns&source=lnms&tbm=isch&ei=LOuKT9DTJ8uxrAf715CnCw&sa=X&oi=mode_link&ct=mode&cd=2&ved=0