The sun is a huge sphere of hot gases that produce tremendous energy and light and make life on Earth possible.
This celestial object is the largest and most massive in the solar system. From Earth to it, the distance is from 150 million kilometers. It takes about eight minutes to reach us with heat and sunlight. This distance is also called eight light minutes.
The star warming our earth consists of several outer layers, such as the photosphere, chromosphere and solar corona. The outer layers of the atmosphere of the Sun create energy on the surface that bubbles and escapes from the insides 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 sphere of light. The photosphere is marked by bright, boiling plasma granules and darker, colder sunspots that occur when solar magnetic fields break through the surface. Spots appear and move across the disk of the Sun. Observing this movement, astronomers concluded that our luminary rotates around its axis. Since the sun does not have a solid foundation, different regions rotate at different speeds. The equatorial regions go full circle in about 24 days, while the polar rotation 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 X-ray and radio emission is directly the solar corona.
What is the chromosphere?
The area surrounding the photosphere, which is the outer shell of the Sun, is called the chromosphere. A narrow region separates the corona from the chromosphere. Temperature rises sharply in the transition region, from several thousand degrees in the chromosphere to more than a million degrees in the corona. The chromosphere emits a reddish glow, as from the combustion of superheated hydrogen. But the red rim can only be seen during an eclipse. At other times, the light from the chromosphere is usually too weak to see it against the background of the bright photosphere. Plasma density drops rapidly, moving through the transition region upward from the chromosphere to the corona.
What is a solar corona? Description
Astronomers tirelessly conduct research on the mystery that the solar corona conceals. 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 corona extend far into space and, in fact, reach the Earth’s orbit. The shape is mainly determined by the magnetic field. Free electrons in coronal motion along the lines of force of magnetic fields form many different structures. The forms that are observed in the corona above sunspots often have a horseshoe-shaped shape, which once again confirms that they follow the lines of the magnetic field. From the top of such “arches,” long stretch marks can spread, at a distance of the diameter of the Sun or even more, as if some process was pulling the material from the top of the arches into space. This involves the solar wind, which gets out through our solar system. Astronomers called these phenomena the “serpentine helmet” because of their similarity to the serrated 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 rarefied plasma. The temperature inside the corona 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 detected at wavelengths that do not correspond to known materials. In this regard, astronomers have suggested the existence of "coronium" as the main gas in the corona. The true nature of this phenomenon remained a mystery until it was discovered that coronal gases were superheated above 1.000.000 ° C. With such a high temperature, the two dominant elements - hydrogen and helium - are completely devoid of their electrons. Even minor substances such as carbon, nitrogen and oxygen are stripped to bare nuclei. Only the heavier constituents (iron and calcium) are able to retain some of their electrons under the influence of such temperatures. The radiation from these highly ionized elements that form the 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 eyes; the corona of the sun is also 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 a solar eclipse occurs or with the help of a special telescope-coronograph that simulates an eclipse, covering a bright solar disk. Some coronographs use ground-based telescopes, others are conducted on satellites.
The brightness of the solar corona in x-rays is due to its enormous temperature. The solar photosphere, on the other hand, emits very few x-rays. This allows you 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 you to see x-rays. In the early 70s, the first US space station Skylab used an X-ray telescope, with which the sun's corona and sunspots or holes were clearly visible for the first time. Over the past decade, a wealth of information and images have been provided on the corona of the sun. With the help of satellites, the solar corona becomes more accessible for new and interesting observations of the Sun, its features and dynamic nature.
Sun temperature
Although the internal structure of the solar core is hidden from direct observation, 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 corona, in the region of 500 kilometers above the photosphere.
The sun is hotter on the inside than on the outside. However, the outer atmosphere of the Sun, the corona, is indeed hotter than the photosphere.
In the late thirties, Grotrian (1939) and Edlen discovered that the 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 stages of ionization. They concluded that coronal gas is very hot with a temperature of over 1 million degrees.
The question of why the solar corona is so hot remains one of the most exciting astronomy puzzles in 60 years. There is no clear answer to this question yet.
Although the solar corona is disproportionately hot, it also has a very low density. Thus, only a small fraction of the total solar radiation is required to replenish the corona. The total power emitted in x-rays is only about one millionth of the total luminosity of the sun. An important question is how energy is transported to the corona and what mechanism is responsible for transport.
The mechanisms of nutrition of the solar corona
Over the years, several different mechanisms for feeding the crown have been proposed:
Acoustic waves.
Fast and slow magneto-acoustic waves tel.
Alfvén wave bodies.
Slow and fast magneto-acoustic surface waves.
Current (or magnetic field) - dissipation.
Particle flows and magnetic flux.
These mechanisms have been tested both theoretically and experimentally and to date only acoustic waves have been excluded.
It has not yet been studied where the upper border of the crown ends. Earth and other planets of the solar system are located inside the corona. The optical radiation of the corona is observed over 10–20 radii of the Sun (tens of millions of kilometers) and combines with the phenomenon of the zodiacal light.
Magnetic Carpet of the Solar Corona
Recently, the "magnetic carpet" has been associated with the puzzle of coronal heating.
Observations with high spatial resolution show that the surface of the Sun is covered with 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 electric current.
Recent observations of this “magnetic carpet” show interesting dynamics: photospheric magnetic fields are constantly moving, interacting with each other, scattering and coming out for a very short period of time. A magnetic reconnection between a magnetic field of opposite polarity can change the field topology 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, it cannot be argued that the “magnetic carpet” ultimately solves the problem of heating the corona, since a 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 such as: “The sun will go out soon” or, conversely, “The temperature of the sun will rise and life on Earth will soon become impossible” sounds at least ridiculous. Who can make such predictions without knowing exactly what mechanisms are at the heart of this mysterious star ?!