Physics of auroral phenomena : proceedings of the 33rd Annual seminar, Apatity, 02 - 05 March, 2010 / [ed.: A.G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 206 с. : ил.

А. V. Germanenko at al. o f tens or hundreds of KeV in the air, it is expected that only particles produced no higher than 300-600 m can reach the ground level. This is also confirmed by the fact that almost all registered increases we observed in the overcast with the lower edge of the clouds from 200 to 600 m. The expression that describes the spectrum of X-ray radiation at the earth's surface after accounting for losses due to absorption o f both electrons and gamma rays is i N(h v) = | 0 where: I is height o f generation of accelerated electrons. /.и is linear attenuation coefficient of gamma - radiation. Q (E,hv) is differential cross section of bremsstrahlung. к is specific losses o f electrons in the air (220 keV/m). Calculations are made in the energy range of X-ray hv from 0 to 1000 keV (step 4 keV) and for the heights o f the generation of electrons from 100 to 1000 m (step 50 m). Figure 5 shows the results of model calculations according to formula (8) of the spectra o f bremsstrahlung photons at the earth surface, produced by accelerated electrons in the atmospheric layer o f thickness 1 for different values o f this parameter from 450 to 650 meters. Thick curve shows the spectrum o f photons measured in the event of March 8, 2010 (Fig. 5). It is evident that the measured spectrum agrees well with the model obtained for the generation altitude of 500 m with an integral exponential spectrum with E0= 100 keV. E n e r g y , K eV Fig.5. Comparison o f model spectra (color curves) with the experimental one (black line) 5. Conclusions Continuous measurements (monitoring) by X-ray spectrometer in the atmospheric surface layer o f the Arctic (Spitsbergen archipelago) and subArctic (Apatity) regions discovered systematic relationships between increases in the low-energy gamma (X-ray) background and precipitation as rains and snowfalls at a low and dense cloudiness. As the reason of X-ray increases the bremsstrahlung X-ray radiation produced by electrons, accelerated in electric fields inside rain clouds is suggested. The calculated X-ray spectrum obtained in the model assumptions, are in satisfactory agreement with measurements. R eferences 1.de Mendonga R.R.S., Raulin J.-P., Makhmutov V, Stozhkov Y, Kvashnin A., Maksumov O., Mizin S. and Fernandez G. Long-term and tranient time evolution of cosmic ray fluxes detected in Argentina in association with rain precipitation and atmospheric electricity time variations // Proc. 30th Russian cosmic ray conf., St. Petersburg, 2008. 2. Khaerdinov N.S.: Study o f short time variations o f secondary cosmic rays influenced by electric fields during thunderstorms. //PhD thesis, INR, Moscow, 2006. 3.L. L. Lazutin: Physics and chemistry in space; 14 - X-ray emission o f auroral electrons and magentospheric dynamics. Springer, Berlin (1986), 220 p. 4.J.A. Chalmers: Atmospheric Electricity / / Pergamon press, Oxford, 1974. 420p. 5. G.A. Bete, Y. Ashkin in Experimental Nuclear Physics (E. Segre ed.) // Wiley, New-York, 1953, p. 143-300. 6. W. Heitler: The Quantum theory of Radiation // Oxford, 1954, 492p. exp - E +(k-x) dE dx’ (8) 166