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Radiation is an important and dangerous factor in contemporary reality in some regions of industrial countries, after technological accidents at nuclear objects, chemical enterprises, etc. This is also the reality of some contemporary military activities and armed conflicts. Radiation damages of organisms can arise also due to the natural reasons — aviation or space flights at high altitudes or even long stay on mountain heights. Natural reasons of such effects have been studied insufficiently for today. Purpose. To outline briefly some results of studies of the characteristics of ionizing radiation at different heights above the Earth. To describe briefly the influence of radiation factors on biological organisms and main mechanisms of these effects. To describe effects that cause pathological changes in organisms of people exposed to the low doses of radiation for a long time and methods of post-radiation rehabilitation of affected people in highlands conditions. Methods. Space satellite exploring of the Earth atmosphere at different altitudes above sea level with measurements of different characteristics of solar and galactic radiation (mainly X-ray, gamma radiation, as well as other types of ionizing radiation in some other ranges). Comparative analysis of the results of longterm observation of patients in hospital conditions using many standard laboratory methods of their states examinations. The conducted scientific research consisted of a complex of methodological techniques and approaches: clinical and physiological studies of respiratory and cardiovascular systems, hematological and immunological states, and functional state of higher nervous activity, mental and neurotic state; administration of antihypoxants, histochemical, biophysical and other methods were used to evaluate oxybiotic processes. Mathematical processing of the results, as well as methods of mathematical modeling was applied. Results. The results of the measurements of ionizing radiation levels during the satellite exploring of the Earth atmosphere at different altitudes were analyzed and presented in schemes. The mechanisms of damaging radiation effects in organisms at nano level were described: water radiolysis, “oxygen effect” as radio sensitizer, formation of various types of free radicals and peroxides with future consequences for organic compounds, cells, tissues, organs, and organisms. The results of medical treatment and rehabilitation at the EMBS of the persons irradiated by the low doses of radiation were presented, observed and discussed. Many of represented results were obtained thanks to the collective work of the great commands of our predecessors in science who searched for the possibilities of medical treatment and rehabilitation of patients who obtained low doses of radiation during long time. The contemporary results of possibilities of some developed pathological states pharmacological corrections were discussed; practical recommendations were done. Conclusions. Some of results of fulfilled works, which can be valuable in the treatment and rehabilitation of people of various contingents exposed to low doses of radiation of various natures for a long time, were presented. The outlined recommendations can be offered to persons of various radiation risk contingents for the purposes of their rehabilitation, in practice of health care, etc.

Within the framework of a linear theory, the instability of an electron beam with a finite radius in a cold magnetised boundless plasma is considered. It is shown that a finite beam dimension influences the generation of quasi-potential waves in two aspects: the perpendicular wave number is quantised so that the frequencies of the waves are subjected to strong selection; a new kind of instability appears due to wave energy losses by emission into surrounding space. Growth rate dependence of wave numbers and frequencies is investigated for typical parameters of experiments with electron beams in space.

Within the framework of a linear theory, the instability of an electron beam with a finite radius in a cold magnetised boundless plasma is considered. It is shown that a finite beam dimension influences the generation of quasi-potential waves in two aspects: the perpendicular wave number is quantised so that the frequencies of the waves are subjected to strong selection; a new kind of instability appears due to wave energy losses by emission into surrounding space. Growth rate dependence of wave numbers and frequencies is investigated for typical parameters of experiments with electron beams in space.