Physics of auroral phenomena : proceedings of the 34th Annual seminar, Apatity, 01 - 04 March, 2011 / [ed.: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 231 с. : ил.

А. V. Germanenko et al. I ou N (h v )= J[exp(u(Ai/) •(/-* ))• jQ (E ,hv)-ex p 0 hv -------- (k -x) +AE) dE\bc (3) where: / is height of generation of accelerated electrons, // is linear attenuation coefficient of gamma - radiation, Q(E,hv) is differential cross section of bremsstrahlung, к is specific energy losses of electrons in the air, AE is extra energy of electrons from acceleration in electric field in clouds. Calculations are made in the energy range of X-ray hv from 0 to 1000 keV (step 5 keV) and for the heights of the generation of electrons from 100 to 1000 m (step 50 m). Figure 2 shows the results of model calculations according to formula (3) of the spectra of bremsstrahlung photons at the earth surface, produced by accelerated electrons in the atmosphere at height 1 for different values of this parameter from 300 to 500 meters. Thick curve shows the spectrum of photons measured in the event of March 8, 2010 (Fig. lb). It is evident that the measured spectrum agrees well with the model obtained for the generation altitude band of 200-300 meters with an integral exponential spectrum with E0= 100 keV. According to our model calculations under the formula 3 the increase of field gradient Ez at 1 kV/m, gives increasing of a flux of X-rays on the ground level approximately at 1%. This agrees well with the data of observations. 100 300 meters 400 meters 500 meters experimental spectrum 50 100 150 200 250 300 350 400 Energy, keV Fig. 2. Comparison of model spectra for different altitudes (1, 2 and 3) with the experimental one (black line). 7. Conclusions Continuous measurements (monitoring) by X-ray spectrometer in the atmospheric surface layer of 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 the secondary cosmic ray 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. References [1] Alexeenko V.V. et al. Physics Letters, 2002, A301, 299-306. [2] de Mendoza R.R.S., et al. JATSTP, 2010, doi:10.1016 /j.jastp. 2010.09.034. [3] Chilingarian A., et al., Phys. Review, 2010, D82, 043009 1-11. [4] Grefenstette B. W., et al., J. Geophys. Res., 2009 114, A02314, doi: 10.1029/2008JA013721. [5] Lehtinen N.G., et al. Geophys. Res. Lett. 24, 1997, №21, 2639-2642. [6] Gurevich, A. V., et al. Phys. Lett. A , 1992, 165,463-468. [7] Rust W.D. and Trapp R J, Geophys. Res. Lett. 29,2002, №20, 1959. [8] Lazutin L.L. X-ray emission of auroral electrons and magentospheric dynamics. Springer, Berlin, 1986, 220 p. 188