48 years have passed since the announced first flight of astronauts to the Moon, but humanity, doubting their reality, still asks hundreds of questions, most of which remain unanswered. Many are interested in how the Americans managed to solve the issue of radiation protection in such a way that for half a century this secret technology was never seen anywhere. NASA thought and pondered for a long time on the issue of the Allen belt and finally decided to throw the bone - all 11 flights were carried out with a “favorable green light”, through established corridors that were safe for movement:
The radiation belt seems to be not the same, and has different levels of radiation in different places, right? In addition, if you rush through quickly, you can avoid a large dose. In my amateurish opinion, of course
More recently, in 2014, another video was released where NASA was still solving problems with this harmful radiation.
Earth's radiation belt
Another name (usually in Western literature) is “Van Allen radiation belt”.
Inside the magnetosphere, as in any dipole field, there are areas inaccessible to particles with kinetic energy E, less than critical. The same particles with energy E < E kr, who are already there, cannot leave these areas. These forbidden regions of the magnetosphere are called capture zones. In the capture zones of the Earth's dipole (quasi-dipole) field, significant fluxes of captured particles (primarily protons and electrons) are indeed retained.
The Earth's radiation belt (inner) was predicted by Soviet scientists S.N. Vernov and A.E. Chudakov, as well as the American scientist James Van Allen. The existence of the radiation belt was demonstrated by measurements on Sputnik 2, launched in 1957, and also on Explorer 1, launched in 1958. To a first approximation, the radiation belt is a toroid, in which two regions are distinguished:
- an inner radiation belt at an altitude of ≈ 4000 km, consisting predominantly of protons with energies in the tens of MeV;
- outer radiation belt at an altitude of ≈ 17,000 km, consisting predominantly of electrons with energies in the tens of keV.
The height of the lower boundary of the radiation belt varies at the same geographical latitude in longitude due to the inclination of the axis of the Earth's magnetic field to the axis of rotation of the Earth, and at the same geographical longitude it changes in latitude due to the own shape of the radiation belt, due to different height of the Earth's magnetic field lines. For example, over the Atlantic, the increase in radiation intensity begins at an altitude of 500 km, and over Indonesia at an altitude of 1300 km. If the same graphs are plotted as a function of magnetic induction, then all measurements will fit on one curve, which once again confirms the magnetic nature of particle capture.
There is a gap between the inner and outer radiation belts, located in the range from 2 to 3 Earth radii. Particle fluxes in the outer belt are greater than in the inner one. The composition of the particles is also different: in the inner belt there are protons and electrons, in the outer belt there are electrons. The use of unshielded detectors has significantly expanded information about radiation belts. Electrons and protons with energies of several tens and hundreds of kiloelectronvolts, respectively, were discovered. These particles have a significantly different spatial distribution (compared to penetrating particles).
The maximum intensity of low-energy protons is located at a distance of about 3 Earth radii from its center. Low-energy electrons fill the entire capture region. For them there is no division into internal and external belts. It is unusual to classify particles with energies of tens of keV as cosmic rays, but radiation belts are a single phenomenon and should be studied in conjunction with particles of all energies.
The proton flux in the inner belt is quite stable over time. Early experiments showed that high energy electrons ( E> 1-5 MeV) are concentrated in the outer belt. Electrons with energies less than 1 MeV fill almost the entire magnetosphere. The inner belt is very stable, while the outer one experiences sharp fluctuations.
Radiation belts of planets
Due to the presence of a strong magnetic field, the giant planets (Jupiter, Saturn, Uranus and Neptune) also have strong radiation belts, reminiscent of the outer radiation belt
The beginning of astronautics was marked by a number of discoveries, one of which was the discovery of the Earth's radiation belts. The Earth's inner radiation belt was discovered by American scientist James van Allen after the Explorer 1 flight. The Earth's outer radiation belt was discovered by Soviet scientists S. N. Vernov and A. E. Chudakov after the Sputnik-3 flight in 1958.
At some altitudes, the first satellites fell into areas that were densely saturated with charged particles with very high energy, sharply different from previously observed cosmic particles, both primary and secondary. After processing data from satellites, it became clear that we are talking about charged particles captured by the Earth's magnetic field.
It is known that any charged particles, once in a magnetic field, begin to “wrap” around the magnetic field lines, simultaneously moving along them. The dimensions of the turns of the resulting spiral depend on the initial speed of the particles, their mass, charge and the strength of the Earth's magnetic field in the region of near-Earth space into which they flew and changed the direction of movement.
The Earth's magnetic field is not uniform. At the poles it “condenses” - becomes denser. Therefore, a charged particle that has begun to move in a spiral along the magnetic line “ridden” by it from a region close to the equator, as it approaches any pole, experiences more and more resistance until it stops. And then it returns back to the equator and further to the opposite pole, from where it begins to move in the opposite direction. The particle finds itself, as it were, in a giant “magnetic trap” of the planet.
These regions of the magnetosphere, where high-energy charged particles (mainly protons and electrons) and particles with kinetic energy E less than critical accumulate and are retained, are called radiation belts. The Earth has three radiation belts, and now a fourth has been discovered. The Earth's radiation belt is a toroid.
The first such belt begins at an altitude of approximately 500 km above the western and 1500 km above the eastern hemisphere of the Earth. The largest concentration of particles in this belt - its core - is located at an altitude of two to three thousand kilometers. The upper limit of this belt reaches three to four thousand kilometers above the Earth's surface.
The second belt extends from 10-11 to 40-60 thousand km with a maximum particle density at an altitude of 20 thousand km.
The outer belt begins at an altitude of 60-75 thousand km.
The given boundaries of the belts are still only approximately determined and, apparently, change periodically within some limits.
These belts differ from each other in that the first of them, closest to the Earth, consists of positively charged protons with very high energy - about 100 Moe. Only the densest part of the Earth's magnetic field could capture and hold them. The flow of protons in it is quite stable over time and does not experience sharp fluctuations.
The second belt consists mainly of electrons with energies of “only” 30-100 keV. Larger flows of particles move in it than in the inner belt, and it experiences sharp fluctuations.
In the third belt, where the Earth's magnetic field is weakest, particles with an energy of 200 eV or more are retained.
In addition, electrons with energies less than 1 MeV fill almost the entire capture region. There is no division into belts for them; they are present in all three belts.
To understand how dangerous charged particles in radiation belts are for all life on Earth, let’s give an example for comparison. Thus, ordinary X-ray radiation, used briefly for medical purposes, has an energy of 30-50 keV, and powerful installations for x-raying huge ingots and blocks of metal - from 200 keV to 2 MeV. Therefore, the most dangerous for future cosmonauts and for all living things when flying to other planets are the first and second belts.
That is why scientists are now trying so hard and carefully to clarify the location and shape of these belts, and the distribution of particles in them. So far only one thing is clear. The corridors for habitable spacecraft to enter routes to other worlds will be areas close to the Earth's magnetic poles, free from high-energy particles.
The natural question is: where did all these particles come from? They are mainly thrown out from its depths by our Sun. It has now been established that the Earth, despite its enormous distance from the Sun, is located in the outermost part of its atmosphere. This, in particular, is confirmed by the fact that every time solar activity increases, and therefore the number and energy of particles emitted by the Sun increase, the number of electrons in the second radiation belt increases, which, as if under the pressure of the “wind” of these particles, is pressed towards Earth.
The separation of charges into layers and the formation of the Earth's radiation belts occurs under the influence of the acousto-magnetoelectric effect, which consists in the fact that short-wave radiation from the Sun, passing through the plasma across the lines of force of the Earth's magnetic field, sorts the charges according to their energy state into different levels. The presence of a certain number of charges in each layer, including on the surface of the Earth, gives reason to assume that the Earth, together with the entire atmosphere, can be considered as an electrical machine, which in design can be identified with a spherical multilayer, multi-rotor, asynchronous electrical capacitive-inductive machine.
Particles captured in the Earth's magnetic trap under the influence of the Lorentz force undergo oscillatory motion along a spiral trajectory along the magnetic field line from the Northern Hemisphere to the Southern Hemisphere and back. At the same time, the particles move more slowly (longitudinal drift) around the Earth.
When a particle moves in a spiral in the direction of increasing magnetic field (approaching the Earth), the radius of the spiral and its pitch decrease. The particle velocity vector, remaining unchanged in magnitude, approaches a plane perpendicular to the direction of the field. Finally, at a certain point (called a mirror point) the particle is “reflected”. It begins to move in the opposite direction - to the conjugate mirror point in the other hemisphere.
A proton with an energy of ~ 100 MeV completes one oscillation along the field line from the Northern Hemisphere to the Southern Hemisphere in a time of ~ 0.3 sec. The residence time (“life”) of such a proton in a geomagnetic trap can reach 100 years (~ 3×109 sec), during which time it can make up to 1010 oscillations. On average, captured high-energy particles make up to several hundred million oscillations from one hemisphere to the other.
Longitudinal drift occurs at a much lower speed. Depending on the energy, the particles make a full revolution around the Earth in a time from several minutes to a day. Positive ions drift westward, and electrons drift eastward. The motion of a particle in a spiral around a magnetic field line can be represented as consisting of a rotation about the so-called. instantaneous center of rotation and translational movement of this center along the line of force.
Recently, American physicists solved the mystery of the Van Allen belts - special zones in which high-energy electrons and protons that penetrate the magnetosphere accumulate and are retained. It turned out that in fact they do not protect our planet at all from these very high-energy particles, since they become so after hitting the belts.
Higgs boson: scientists have found the “God particle”
Let me remind you that radiation belts in the magnetosphere of our planet were discovered in the 50s of the last century. American scientist James van Allen, as well as domestic physicists S.N. Vernov and A.E. Chudakov, having analyzed data from the Explorer-1 and Sputnik-3 satellites, came to the conclusion that there are belts near the Earth - mainly protons and electrons. And not one, but two - the first is located on average at an altitude of 4000 km above the earth's surface and consists mainly of protons with energies of tens of MeV.
The second belt is located much higher - somewhere at an altitude of 17,000 km, and it contains mainly electrons with energies of tens of keV. It is also known that between the inner and outer radiation belts there is a gap located in the range from 2 to 3 Earth radii. It should be noted that particle flows in the outer belt are more abundant than in the inner one. At the same time, there is no rigid boundary between the belts - for example, over the Atlantic, the lower belt can descend to an altitude of 500 km, and over Indonesia - up to 1300 km.
In English-language literature, these belts are traditionally called Van Allen belts - in honor of one of the discoverers. However, James van Allen, although he was able to detect streams of high-energy particles in the magnetosphere, still could not give an exact answer to the question of how they appear there. Later, a hypothesis was formulated that high-energy electrons from the far corners of our planet’s magnetosphere enter the outer belt. Once in the capture zone (regions inaccessible to particles with kinetic energy less than critical, from which electrons with these characteristics that have entered there can no longer escape), these particles accelerate and form the well-known ring-like structures of the belt itself.
However, evidence has recently accumulated that is somewhat inconsistent with this explanation. In particular, if everything were exactly like this, then many parameters of the Van Allen belts, for example, particle density, would change quite slowly, that is, over the course of days and weeks. However, this happens much faster - for example, when in 2012 NASA launched a pair of probes specifically designed to study the belts, it turned out that last October the same electron density in the outer one increased a thousand times in less than 12 hours!
After analyzing the results obtained, a group of physicists Jeffrey Reeves from Los Alamos National Laboratory (USA) came to the conclusion that everything happens somewhat differently. In fact, electric fields inside the belts strip electrons from atoms wandering in outer space and accelerate them to near-light speeds. The model they built showed that such processes can change the parameters of the belts in a time from a couple of seconds to several hours, that is, quite quickly.
It is interesting that similar versions have already been expressed by scientists before - for example, satellite observations in the 90s showed exactly the same rate of change in the electron density in the upper Van Allen belt. However, this was recorded only in small areas of this belt, which made physicists doubt that this process is a general pattern. As a result, they decided that the satellite instruments were dealing with some kind of local anomaly, the causes of which could not be established. However, now, since a sharp increase in density was recorded almost throughout the entire belt, it became clear that the hypothesis of electron capture from cosmic atoms is absolutely correct.
Moreover, the research of Dr. Reeves and his colleagues showed that electrons do not come from space already possessing high energies, but receive them already in the Van Allen belts, which, as it turns out, act as natural particle accelerators similar to those found in many earthly physical institutes. It also follows that the idea that radiation belts only protect the earth from the flow of cosmic particles is completely wrong - after all, in practice, most electrons (and, most likely, protons) become high-energy after they are captured, that is, entering the Van Allen belts.
Studies have shown that radiation belts in space begin at 800 km above the Earth's surface and extend up to 24,000 km. Since the radiation level there is more or less constant, the incoming radiation should be approximately equal to the outgoing radiation. Otherwise, it would either accumulate until it “baked” the Earth, as in an oven, or it would dry up. Regarding this, Van Allen wrote:
“Radiation belts can be compared to a leaky vessel that is constantly replenished from the Sun and leaks into the atmosphere. A large portion of solar particles overflows the vessel and splashes out, especially in the polar zones, leading to polar lights, magnetic storms and other similar phenomena.”
Radiation from the Van Allen belts depends on the solar wind. In addition, they seem to focus, or concentrate, this radiation within themselves. But since they can only concentrate in themselves what came directly from the Sun, one more question remains open: how much radiation is in the rest of the cosmos?
The Moon does not have Van Allen belts. She also has no protective atmosphere. It is open to all solar winds. If a strong solar flare had occurred during the lunar expedition, a colossal flow of radiation would have incinerated both the capsules and the astronauts on the part of the lunar surface where they spent their day. This radiation is not just dangerous - it is deadly!
In 1963, Soviet cosmologists told the famous British astronomer Bernard Lovell that they did not know of a way to protect astronauts from the deadly effects of cosmic radiation (15, p. 173). This meant that even the much thicker metal shells of the Russian devices could not cope with the radiation. How could the thin, almost foil-like metal used in our capsules protect our astronauts? NASA knew this was impossible. The space monkeys died less than 10 days after returning, but NASA has never told us the true cause of their death.
Most people, even those knowledgeable in space, are not aware of the existence of deadly radiation permeating its expanses. I believe that we owe our ignorance to those people who tell space stories.
In The Illustrated Encyclopedia of Space Technology, the phrase “cosmic radiation” does not appear even once. Moreover, none of the books I have read over the years, except Bill Mauldin's Perspectives on Interstellar Travel, published in 1992, and Astronautical Science and Technology, written by early NASA experts, even mention this serious obstacles to space flights. Looks like I'm getting to know the delicate workings of my government again...
The Russians definitely knew about radiation because as early as the spring of 1961 they had sensors sent to the far side of the Moon. Upon returning to London, Lovell sent the information he had to NASA administrator Hugh Dryden. Dryden ignored her!
Collins mentioned cosmic radiation only twice in his book:
“At least the Moon was far beyond the Earth’s Van Allen belts, which foreshadowed a good dose of radiation for those who visited there, and a fatal dose for those who lingered” (7, p. 62).
Thus, the Van Allen radiation belts surrounding the Earth and the possibility of solar flares require understanding and preparation so as not to expose the crew to increased doses of radiation (7, p. 101).
So what does “understand and prepare” mean? Does this mean that beyond the Van Allen belts, the rest of space is free of radiation? Or did NASA have a secret strategy for sheltering from solar flares after making the final decision on the expedition?