Solar Crown: description, features, brightness and interesting facts

The sun is a huge sphere of hot gases that produce colossal energy and light and make life on Earth possible.

This celestial object is the largest and most massive in the solar system. From the Earth to it the distance is from 150 million kilometers. To get to us heat and sunlight takes about eight minutes. This distance is also called eight light minutes.

The star that warms our earth consists of several outer layers, such as the photosphere, the chromosphere and the solar corona. The outer layers of the Sun's atmosphere create energy on the surface that bubbles and bursts from the viscera of the star, and is defined as sunlight.

The components of the outer layer of the Sun

The layer that we see is called the photosphere or the sphere of light. The photosphere is marked by bright, boiling plasma granules and darker, colder sunspots that arise when solar magnetic fields break through the surface. The spots appear and move around the Sun's disk. Watching this movement, astronomers concluded that our luminary turns around its axis. Since the Sun does not have a solid base, different regions rotate at different speeds. The areas of the equator go full circle in about 24 days, while the rotation of the polar can take more than 30 days (to make a turn).

What is the photosphere?

The photosphere is also a source of solar flares: flames that extend hundreds of thousands of miles above the surface of the Sun. Solar flares produce bursts of X-ray, ultraviolet, electromagnetic radiation and radio waves. The source of the X-ray and radio emission is directly the solar corona.

What is the chromosphere?

The zone surrounding the photosphere, which is the outer shell of the Sun, is called the chromosphere. A narrow region separates the corona from the chromosphere. The temperature rises sharply in the transition region, from several thousand degrees in the chromosphere to more than a million degrees in the crown. The chromosphere radiates a reddish glow, both from the combustion of superheated hydrogen. But the red rim can be seen only during the eclipse. At other times, the light from the chromosphere, as a rule, is too weak to be seen against the background of a bright photosphere. The plasma density decreases rapidly, through the transition region it moves upward from the chromosphere to the corona.

What is the solar corona? Description

Astronomers are constantly carrying out research on the riddle, which conceals the solar corona. What is she like?

This is the atmosphere of the Sun or its outer layer. This name was given because its appearance becomes apparent when a total solar eclipse occurs. Particles from the crown extend far into space and, in fact, reach the Earth's orbit. The shape is mainly determined by the magnetic field. Free electrons in the corona motion along the lines of force of magnetic fields form a variety of different structures. Forms that are observed in the corona over sunspots often have horseshoe-shaped outlines, which again confirms that they follow the lines of the magnetic field. From the top of such "arches" long stretches can spread, at a distance of the diameter of the Sun or even more, as if some process pulls the material from the top of the arches into space. This involves the solar wind, which falls outside through our solar system. Astronomers called such phenomena "serpentine helmet" because of their similarity to the jagged helmets worn by knights and used by some German soldiers until 1918.

What does the crown consist of?

The material from which the solar corona is formed is extremely hot, consisting of a rarefied plasma. The temperature inside the crown is more than a million degrees, surprisingly, much higher than the temperature on the surface of the sun, which is about 5500 ° C. The pressure and density of the corona are much lower than in the Earth's atmosphere.

Observing the visible spectrum of the solar corona, bright emission lines were found at wavelengths that did not correspond to known materials. In this connection, astronomers have suggested the existence of a "crown" as the main gas in the crown. The true nature of this phenomenon remained a mystery until it was discovered that the coronal gases overheated above 1,000,000 ° C. In the presence of such a high temperature, the two dominant elements, hydrogen and helium, are absolutely devoid of their electrons. Even minor substances such as carbon, nitrogen and oxygen are stripped to bare cores. Only heavier components (iron and calcium) are able to retain some of their electrons under the influence of such temperatures. The radiation from these highly ionized elements, which form spectral lines, until recently remained mysterious for early astronomers.

Brightness and interesting facts

The solar surface is too bright and, as a rule, our solar atmosphere is inaccessible to our sight, the crown of the Sun too is not visible to the naked eye. The outer layer of the atmosphere is very thin and weak, so it can be seen only from the Earth at a time when there is a solar eclipse or by means of a special telescope-coronagraph that simulates an eclipse covering a bright solar disk. Some coronagraphs use ground-based telescopes, others are carried out by satellites.

The brightness of the solar corona in X-rays is due to its huge temperature. On the other hand, the solar photosphere emits very few X-rays. This allows us to view the corona on the disk of the Sun, when we observe it in X-rays. For this, special optics are used, which allows to see X-rays. In the early 1970s, the first US space station Skylab used an X-ray telescope, which clearly showed the solar corona and sunspots or holes for the first time. During the last decade, a huge amount of information and images on the Sun's crown was provided. With the help of satellites, the solar corona becomes more accessible for new and interesting observations of the Sun, its features and dynamic character.

Temperature of the Sun

Although the internal structure of the solar core is hidden from direct observations, it can be concluded, using various models, that the maximum temperature inside our star is about 16 million degrees (Celsius). The photosphere - the visible surface of the Sun - has a temperature of about 6000 degrees Celsius, but it increases very sharply from 6000 degrees to several million degrees in the crown, about 500 kilometers above the photosphere.

The sun is hotter on the inside than on the outside. However, the outer atmosphere of the Sun, the crown, is really hotter than the photosphere.

In the late thirties, Grotrian (1939) and Edlene discovered that strange spectral lines observed in the spectrum of the solar corona are emitted by elements such as iron (Fe), calcium (Ca), and nickel (Ni) in very high ionization stages. They came to the conclusion that the coronal gas heated up strongly with a temperature of more than 1 million degrees.

The question of why the solar corona is so hot remains one of the most exciting puzzles of astronomy in the last 60 years. There is no single answer to this question.

Although the solar corona is immeasurably hot, it also has a very low density. Thus, only a small part of the total solar radiation is required to make up the corona. The total power radiated in X-rays is only about one millionth of the total solar luminosity. An important question is how the energy is transported to the crown and which mechanism is responsible for transport.

Mechanisms of feeding the solar corona

Over the years, several different mechanisms for feeding the crown have been proposed:

• Acoustic waves.

• Fast and slow magneto-acoustic waves of bodies.

• Alfvén's waves.

• Slow and fast magneto-acoustic surface waves.

• Current (or magnetic field) - scattering.

• Streams of particles and magnetic flux.

These mechanisms were tested both theoretically and experimentally and to date only acoustic waves have been excluded.

So far, it has not been studied where the upper border of the crown ends. Earth and other planets of the solar system are located inside the crown. Optical radiation of the corona is observed at 10-20 solar radii (tens of millions of kilometers) and is combined with the phenomenon of zodiacal light.

Magnetic carpet of the solar corona

Recently, the "magnetic carpet" was associated with a puzzle of coronal heating.

Observations with high spatial resolution show that the surface of the Sun is covered by weak magnetic fields, concentrated in small areas of opposite polarity (carpet magnet). These magnetic concentrations are believed to be the main points of individual magnetic tubes carrying an electric current.

Recent observations of this "magnetic carpet" show interesting dynamics: the photospheric magnetic fields constantly move, interact with each other, dissipate and leave for a very short period of time. A magnetic reconnection between a magnetic field of opposite polarity can change the topology of the field and release magnetic energy. The reconnection process will also lead to the dissipation of electrical currents that convert electrical energy into heat.

This is a general idea of how a magnetic carpet can be involved in coronal heating. However, to assert that the "magnetic carpet" ultimately solves the problem of heating the corona is impossible, since the quantitative model of the process has not yet been proposed.

Can the sun go out?

The solar system is so complex and unexplored that sensational statements like "The sun will soon go out" or, on the contrary, "The temperature of the Sun rises and soon life on Earth becomes impossible" sounds at least ridiculous. Who can make such predictions, without knowing exactly what mechanisms are behind this mysterious star ?!