What is the Aurora Borealis? - Seeker
These high-energy particles and radiations get released into space and travel throughout the solar system. When they hit the Earth, they encounter its magnetic . 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 Other aboriginal peoples believed that the lights were the spirits of their people. If you're near the North Pole, it is called an aurora borealis or northern The protective magnetic field around Earth shields us from most of the.
October 11, Shawn Malone The northern lights, or aurora borealis, offer an entrancing, dramatic, magical display that fascinates all who see it — but just what causes this dazzling natural phenomenon?Aurora Borealis in Hindi - Northern lights - aurora Borealis meaning
At the center of our solar system lies the sun, the yellow star that sustains life on our planet. The sun's many magnetic fields distort and twist as our parent star rotates on its axis. Usually, these sunspots occur in pairs; the largest can be several times the size of Earth's diameter.
This image from NASA's Solar Dynamics Observatory shows the sun as it appeared in extreme ultraviolet wavelengths on March 5, just after a major solar flare. As the temperature on its surface rises and falls, the sun boils and bubbles. Particles escape from the star from the sunspot regions on the surface, hurtling particles of plasma, known as solar wind, into space.
It takes these winds around 40 hours to reach Earth. When they do, they can cause the dramatic displays known as the aurora borealis. The gas giants in our solar system Jupiter, Saturn, Uranus and Neptune each have thick atmospheres and strong magnetic fields, and each have auroras — although these auroras are a little different from Earth's, given they are formed under different conditions.
Venus has an aurora generated by its stretched-out magnetic field a "magnetotail". Mars, which has too thin an atmosphere for global auroras, experiences local auroras due to magnetic fields in the crust.
Sunspots and cycles The sunspots and solar storms that cause the most magnificent displays of the northern lights occur roughly every 11 years. The solar cycle peaked inbut it was the weakest solar maximum in a century. Since record-keeping of the ebb and flow of the sun's activity began inthere have been 22 full cycles. Researchers monitor space weather events because they have the potential to affect spacecraft in orbit, knock out power grids and communications infrastructure on Earth, and amp up normal displays of the northern and southern lights.
Aurora Borealis: What Causes the Northern Lights & Where to See Them
Particles and polar attraction Earth is constantly bombarded with debris, radiation and other magnetic waves from space that could threaten the future of life as we know it. Most of the time, the planet's own magnetic field does an excellent job of deflecting these potentially harmful rays and particles, including those from the sun. Particles discharged from the sun travel 93 million miles around million km toward Earth before they are drawn irresistibly toward the magnetic north and south poles.
As the particles pass through the Earth's magnetic shieldthey mingle with atoms and molecules of oxygen, nitrogen and other elements that result in the dazzling display of lights in the sky.
An Expedition 30 crew member took this photo of the North Atlantic with an aurora on March 28, Their southern counterpart, which light up the Antarctic skies in the Southern Hemisphere, are known as the aurora australis. Joan Feynman deduced in the s that the long-term averages of solar wind speed correlated with geomagnetic activity.
The solar wind and magnetosphere consist of plasma ionized gaswhich conducts electricity. It is well known since Michael Faraday 's work around that when an electrical conductor is placed within a magnetic field while relative motion occurs in a direction that the conductor cuts across or is cut byrather than along, the lines of the magnetic field, an electric current is induced within the conductor.
The strength of the current depends on a the rate of relative motion, b the strength of the magnetic field, c the number of conductors ganged together and d the distance between the conductor and the magnetic field, while the direction of flow is dependent upon the direction of relative motion.
Dynamos make use of this basic process "the dynamo effect "any and all conductors, solid or otherwise are so affected, including plasmas and other fluids. The IMF originates on the Sun, linked to the sunspotsand 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 angles them at Earth by about 45 degrees forming a spiral in the ecliptic planeknown as the Parker spiral.
The field lines passing Earth are therefore usually linked to those near the western edge "limb" of the visible Sun at any time. However, this process is hampered by the fact that plasmas conduct readily along magnetic field lines, but less readily perpendicular to them. Energy is more effectively transferred by temporary magnetic connection between the field lines of the solar wind and those of the magnetosphere.
Aurora - Wikipedia
Unsurprisingly this process is known as magnetic reconnection. As already mentioned, it happens most readily when the interplanetary field is directed southward, in a similar direction to the geomagnetic field in the inner regions of both the north magnetic pole and south magnetic pole. Schematic of Earth's magnetosphere Auroras are more frequent and brighter during the intense phase of the solar cycle when coronal mass ejections increase the intensity of the solar wind. The high latitude magnetosphere is filled with plasma as the solar wind passes the Earth.
The flow of plasma into the magnetosphere increases with additional turbulence, density and speed in the solar wind.
This flow is favoured by a southward component of the IMF, which can then directly connect to the high latitude geomagnetic field lines. In addition to moving perpendicular to the Earth's magnetic field, some magnetospheric plasma travels down along the Earth's magnetic field lines, gains additional energy and loses it to the atmosphere in the auroral zones. The cusps of the magnetosphere, separating geomagnetic field lines that close through the Earth from those that close remotely allow a small amount of solar wind to directly reach the top of the atmosphere, producing an auroral glow.
On 26 FebruaryTHEMIS probes were able to determine, for the first time, the triggering event for the onset of magnetospheric substorms. It is not well understood, but geomagnetic storms may vary with Earth's seasons. Two factors to consider are the tilt of both the solar and Earth's axis to the ecliptic plane.
Northern Lights or Aurora Borealis Explained
As the Earth orbits throughout a year, it experiences an interplanetary magnetic field IMF from different latitudes of the Sun, which is tilted at 8 degrees. Similarly, the 23 degree tilt of the Earth's axis about which the geomagnetic pole rotates with a diurnal variation, changes the daily average angle that the geomagnetic field presents to the incident IMF throughout a year. These factors combined can lead to minor cyclical changes in the detailed way that the IMF links to the magnetosphere.
In turn, this affects the average probability of opening a door through which energy from the solar wind can reach the Earth's inner magnetosphere and thereby enhance auroras.
Auroral particle acceleration[ edit ] The electrons responsible for the brightest forms of aurora are well accounted for by their acceleration in the dynamic electric fields of plasma turbulence encountered during precipitation from the magnetosphere into the auroral atmosphere. In contrast, static electric fields are unable to transfer energy to the electrons due to their conservative nature. The increase in strength of magnetic field lines towards the Earth creates a 'magnetic mirror' that turns back many of the downward flowing electrons.
The bright forms of auroras are produced when downward acceleration not only increases the energy of precipitating electrons but also reduces their pitch angles angle between electron velocity and the local magnetic field vector. This greatly increases the rate of deposition of energy into the atmosphere, and thereby the rates of ionisation, excitation and consequent emission of auroral light.
Acceleration also increases the electron current flowing between the atmosphere and magnetosphere. One early theory proposed for the acceleration of auroral electrons is based on an assumed static, or quasi-static, electric field creating a uni-directional potential drop. Fundamentally, Poisson's equation indicates that there can be no configuration of charge resulting in a net potential drop.
Inexplicably though, some authors   still invoke quasi-static parallel electric fields as net accelerators of auroral electrons, citing interpretations of transient observations of fields and particles as supporting this theory as firm fact.
In another example,  there is little justification given for saying 'FAST observations demonstrate detailed quantitative agreement between the measured electric potentials and the ion beam energies Another theory is based on acceleration by Landau  resonance in the turbulent electric fields of the acceleration region. This process is essentially the same as that employed in plasma fusion laboratories throughout the world,  and appears well able to account in principle for most — if not all — detailed properties of the electrons responsible for the brightest forms of auroras, above, below and within the acceleration region.
Wikinews has related news: Aurora Borealis caused by electrical space tornadoes Other processes are also involved in the aurora, and much remains to be learned.
Such low energies excite mainly the red line of oxygen, so that often such auroras are red. On the other hand, positive ions also reach the ionosphere at such time, with energies of 20—30 keV, suggesting they might be an "overflow" along magnetic field lines of the copious "ring current" ions accelerated at such times, by processes different from the ones described above.
These ions are accelerated by plasma waves in directions mainly perpendicular to the field lines. They therefore start at their "mirror points" and can travel only upward.