Northern Lights

Article

July 5, 2022

The aurora borealis (often: aurora borealis in the northern hemisphere, aurora australis in the south) is a temporary light phenomenon caused by charged particles (mainly protons and electrons) entering the atmosphere at the north and south poles of the Earth. It is observed more often (but not constantly) north of the Arctic Circle and south of the Southern Arctic Circle from late autumn to early spring. It is usually not visible from Hungary. Auroras occur when the solar wind stirs up the magnetosphere so much that charged particles from the solar wind and magnetosphere penetrate into the upper atmosphere, attracted by the Earth's magnetic field, where they transfer some of their energy to the atmosphere. As a result, the components of the atmosphere are ionized and excited, emitting light in different colors. Its shape is determined by the movement of the ionized components. The incoming protons are transformed into hydrogen atoms by capturing electrons, thus emitting the colors characteristic of excited hydrogen atoms (red, blue, violet). This is more visible at lower latitudes. The colors of oxygen (red, green) and nitrogen (blue, violet), the most common components of the atmosphere, are also visible.

Location

The aurora is mostly visible at a distance of 10°-20° from the magnetic pole, at a latitude of 3°-6°. It is best observed in the dark sky, during long polar nights, but it can occur at any time of the year and during the day. The area that experiences the auroral light is called the auroral oval, although it is more ribbon-shaped. The connection with the solar wind was discovered during the study of statistics. It was described in more detail by Elias Loomis (1860) and Hermann Fritz (1881) after noticing that it was most often seen here. The daily position can be tracked on the Internet. In the Northern Hemisphere it is known as the Northern Lights. The name aurora borealis comes from Galileo. The name aurora australis was created as a counterpart to this, which appears similar to the northern lights and is created and changes with it. It is also seen at high latitudes in Antarctica, Chile, Argentina, New Zealand and Australia. After strong solar activity, during magnetic storms, the structure of the magnetosphere changes, in which case the aurora borealis can be observed at lower latitudes, so very rarely in Hungary. The aurora is best seen when the magnetic pole is between the observer and the Sun. This period is magnetic midnight, which can be distinguished from normal midnight. In most areas of the United States, this occurs one hour earlier. Magnetic storms in the 11-year cycle of sunspots intensify at the peak or three years after. Carl Størmer and his colleagues analyzed more than 12,000 auroras using cameras. By triangulation, they found that most lights originate between 90 and 150 km above the surface, and sometimes extend over 1,000 km. Green color is usually created at an altitude of 240 km, red above, blue below 100 km, and purple above.

Description

Its name was derived from the name of the Roman goddess of the dawn, Aurora, but it is also known as the Northern Lights (borealis means north and australis means south). The charged particles come predominantly from the Sun (solar wind), and a smaller proportion is made up of particles from outside the Solar System. The charged particles are largely deflected by the Earth's magnetosphere, but they enter the atmosphere in the region around the magnetic poles.

Colors

The particles collide with the atoms of the atmosphere, ionize and excite the atoms, and the excited atoms return to their ground state with light emission. The emitted light on the atom or molecule, respectively