How does auroras form in the ionosphere?

Answer 1

The Aurora Borealis is made when storms on the the sun form solar winds, or large streams of charged particles streaming toward the earth.These streams could have upward of ten million megawatts of electrical power. That is enough power to light up Los Angeles. It generally takes about three days for these streams of particles to reach the earth's upper atmosphere, or ionosphere. When these charged particles hit the earth's atmosphere, they excite the atoms contained in the atmosphere. These excited atoms have a higher energy state that usual and so want to get back to a more normal energy state. The excited atoms give off excess energy in the form of heat, or the case of the aurora borealis, light.

Answer 2

Aurora Borealis (the famous 'Northern Lights') are caused when solar flares emanating from the sun, strike the ionosphere surrounding the Earth. The ionosphere contains many types of chemical molecule, which when heated by the Sun's rays undergo a brief chain reaction. This reaction creates the brilliant and beautiful 'moving light displays' that can be seen from the Earth's far Northern hemisphere.

Answer 3

How is the Ionosphere Formed?

At the outer reaches of the Earth's environment, solar radiation strikes the atmosphere with a power density of 1370 Watts per meter2 or 0.137 Watts per cm2, a value known as the "solar constant." This intense level of radiation is spread over a broad spectrum ranging from radio frequencies through infrared (IR) radiation and visible light to X-rays. Solar radiation at ultraviolet (UV) and shorter wavelengths is considered to be "ionizing" since photons of energy at these frequencies are capable of dislodging an electron from a neutral gas atom or molecule during a collision. The conceptual drawing below is a simplified explanation of this process.

Incoming solar radiation is incident on a gas atom (or molecule). In the process, part of this radiation is absorbed by the atom and a free electron and a positively charged ion are produced. (Cosmic rays and solar wind particles also play a role in this process but their effect is minor compared with that due to the sun's electromagnetic radiation.)

At the highest levels of the Earth's outer atmosphere, solar radiation is very strong but there are few atoms to interact with, so ionization is small. As the altitude decreases, more gas atoms are present so the ionization process increases. At the same time, however, an opposing process called recombination begins to take place in which a free electron is "captured" by a positive ion if it moves close enough to it. As the gas density increases at lower altitudes, the recombination process accelerates since the gas molecules and ions are closer together. The point of balance between these two processes determines the degree of "ionization" present at any given time.

At still lower altitudes, the number of gas atoms (and molecules) increases further and there is more opportunity for absorption of energy from a photon of UV solar radiation. However, the intensity of this radiation is smaller at these lower altitudes because some of it was absorbed at the higher levels. A point is reached, therefore, where lower radiation, greater gas density and greater recombination rates balance out and the ionization rate begins to decrease with decreasing altitude. This leads to the formation of ionization peaks or layers (also called "Heaviside" layers after the scientist who first proposed their existence).

Because the composition of the atmosphere changes with height, the ion production rate also changes and this leads to the formation of several distinct ionization peaks, the "D," "E," "F1," and "F2" layers.

Answer 4

The sun produces continuous solar winds that vary in intensity with the events happening on the surface. These winds are made up of charged particles moving away from the sun at high velocity. The solar wind extends outside of our solar system to be pushed against by the interstellar winds.

Earth has a strong magnetic field. The poles are located near Earth's north and south poles. When the solar wind encounters Earths magnetic field, it compresses the side its coming from. This is called bow shock. It also stretches the opposite side into a long tail. Most of the charged particles are redirected by, and flow along, our magnetic field lines. Since the field is concentrated at the poles, the charged particles are focused at the poles. The effect this interaction of the solar wind with our magnetic field creates a dynamo effect in the space surrounding Earth. If the solar wind is particularly strong, it can fold the forward field back behind the planet which causes greatly increased aurora activity.

When the particles interact with our atmosphere, they ionize some of the gas molecules in the air and make them glow. When the volume of particles traveling down the field lines at the poles increases, it increases the brightness of the aurora and produces more sheets; they also cover more geographical area which allow them to be seen from lower latitudes.

This is how the aurora are formed and sustained.

Answer 5

They are formed by the Earth's Magnetic Field, the Magnetic Field is generated inside the core of the planet.

Answer 6

The Aurora Borealis is in the Thermosphere.

Answer 7

It is formed because of the magnetic field of earth. As charged particles from the sun collide with our magnetic field it makes light.

Answer 8

Charged particles within the solar wind are trapped at the Earth's poles and ionize the molecules in the outer layers of the atmosphere.