Coronal mass ejections

Coronary mass ejection - the ejection of matter from the solar corona . Observation of coronal mass ejections from the Earth's surface is difficult. Apparently, the first observation of coronal ejections in the visible wavelength range was made in the early 1970s using a coronograph installed at the seventh orbital solar observatory . The SMM station continued to study this phenomenon in 1980 ^[1] .

Until the data from these two stations appeared, no one realized that coronal mass ejections are so important and widespread.

Since the eclipse disk of the coronograph cuts out the bright disk of the Sun from the field of view of the device, observations of the source of the coronal ejection on the surface of the Sun with the help of the coronograph are impossible, and assumptions about its possible source are made on the basis of observations by other instruments in other wavelength ranges ^[2] . This fundamental difficulty leads to the fact that, according to observations from a satellite near the Earth, in some cases it is impossible to determine the direction of the ejection: whether it is moving toward the Earth or from the Earth. To overcome this difficulty, a pair of spacecraft of the STEREO project are currently being used, which are separated at large angles in the Earth’s orbit.

During the maximums of solar activity, the frequency of coronal mass ejections reaches three per day, while in periods of a quiet Sun this frequency can decrease to one ejection in 5 days ^[3] .

Unlike solar flares , during which the magnetic energy accumulated in active areas on the Sun is realized mainly in the form of electromagnetic radiation, during coronal mass ejections this energy is spent on the acceleration of huge masses of matter. Coronal mass ejections, which can only be observed outside the solar disk (outside the eclipse disk of the coronograph), are often compared with solar flares that are observed on the solar disk. Since such a comparison is ambiguous, there are 2 points of view on the relationship of these phenomena. According to an earlier point of view, coronal mass ejections and solar flares are different manifestations of the same process. According to the second point of view, these phenomena can have a common energy source, and if there is enough energy accumulated in the energy source to realize 2 phenomena, they occur in intervals close in time and space. However, there are a number of observations when coronal mass ejections are recorded without any phenomena on the solar disk, including without solar flares ^[4] .

The ejection includes a plasma , consisting mainly of electrons and protons, along with a small number of heavier elements - helium , oxygen , and others. Some ions often have lower ionization states (for example, singly ionized helium atoms) than the surrounding quiet plasma of the corona , which indicates that a significant part of the ejection mass can be accelerated from regions with a lower temperature, i.e., from the level of the chromosphere . A characteristic feature of the ejection is that the general ejection topology is in the form of a giant loop, both of which are fixed to the solar atmosphere, and the magnetic field in the ejection is usually higher than in a calm solar wind , and is a magnetic force twisted into a bundle lines. Each coronal mass ejection can contain up to 10 billion tons of matter that flies in space at an average speed of 400 km per second (fast ejections - up to 2000 km / s. If the ejection is directed towards the Earth, it reaches our planet within one to three days. Fast coronal ejections passing through a slower regular solar wind create powerful shock waves in it ^[3] .

There are also distinguished coronal ejection in interplanetary space . One of the varieties of such an ejection is a magnetic cloud. When an ejection reaches the Earth , it can have a strong effect on its magnetosphere , causing various phenomena of space weather . Possible effects include auroras , magnetic storms , disturbances in the operation of electrical equipment, and deterioration of the propagation conditions of radio waves .