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.

“P hysics o f Auroral P hen om ena”, Proc. XXXIII A nnu al Seminar, Apatity, pp. 163 - 166, 2011 © Kola Science Centre, Russian Academy of Science, 2011 Polar Geophysical Institute STUDY OF GAMMA-RADIATION CONNECTED TO ATMOSPHERIC PRECIPITATION A.V. Germ anenko, Yu.V . Balabin, B.B. Gvozdevsky, L.I. Schur, E.V. Vashenyuk (Polar Geophysical Institute KSC RAS, 15, Khalturina Str., Murmansk, 183010, Russia; E-mail: germanenko@pgia. ru). Abstract. Increases in the intensity of gamma - radiation in the surface layer of the atmosphere during precipitation in the arctic and subarctic regions were studied. A clear link between rising and rain (snow) cloud was found out. The mechanism of generation of X-rays during precipitation is supposed. Preliminary evaluations are obtained. 1. Introduction The existence o f excess radiations associated with precipitations and thunderstorms is a well known fact [1- 2]. It was shown that the main cause of the excess radiation during thunderstorms is the particles accelerated by strong electric fields within thunderclouds [2]. We organized monitoring of low-energy gamma (X-ray) background on the ground level and recorded increases, usually associated with precipitations. It should be noted that in the subArctic (Apatity) and Arctic (Spitsbergen) regions, where observations were made, thunderstorms are almost not observed. Nevertheless, as the cause of the increases associated with precipitations, we assume the electric field of the clouds (though not as strong as in thunderstorm clouds), which accelerates electrons and creates the bremsstrahlung radiation penetrating to the ground level. 2. Instrum entation 2.1. Scintillation spectrom eter To monitor gamma (X-ray) - background at the ground level, we used the scintillation spectrometer based on the Nal (Tl), crystal o f 6 cm in diameter and 2 cm thick. The instrument was previously developed and used to measure the auroral X-rays from balloons in the stratosphere [3]. The signal after the photomultiplier and the amplifier comes to the input of 4096 channel pulse analyzer V4K-SATSP-USB, based on the high-speed spectrometric ADC for 4096 channels. The signal after the photomultiplier and the amplifier also is continuously recorded in 4 integral channels with a threshold photon energies> 20,> 60,> 100 and> 200KeV. Outputs of these channels enter a computer through through the interface module and a special programmed extension card AD LINK 7233. Detection in integral channels allows us continuous estimation of the integral spectrum of gamma (X-ray) radiation. Power supply for photomultiplier and an amplifier for it is made using a special circuit of voltage converter with pulse-width modulation, providing good stability of high voltage supply for photomultiplier. Measures are taken for stabilize the temperature inside the instrument container, which is made of aluminum and hermetically sealed. Photomultiplier output pulse enters the amplifier. Parameters of the input amplifier circuit were chosen in such a way that for each 1 KeV at the photomultiplier input had to be 1 mV at the amplifier input. The gain of amplifier was set to 10. Thus, the photon with energy of 100 keV causes at the amplifier output a pulse with amplitude of 1 V. The spectrometers were tested with a source of gamma radiation Am241, which has a weak line at 27 KeV and the main line at 60KeV. The detector is installed in Apatity on the loft, right under the 1 mm thick iron sheet roof. Along the sides and bottom it is surrounded by lead bricks 5 cm thick, for shielding them from the surrounding radiation from buildings and the ground, and placed inside a polyfoam box with a wall thickness of 8 cm. The detector in Barentsburg was installed in the housing of the central section of the neutron monitor and placed inside cylindrical steel "cup" with a wall thickness of 8 mm, which allows registration of arriving X-rays only from the top hemisphere. 2.2 Add itional equipm ent Together with spectrometers in Apatity a precipitation gauge was installed that allowed us to evaluate the intensity o f precipitation in the form o f rain and snow. The neutron monitor housing in Barentsburg also incorporates sensors outside and inside temperatures. 3. O b servations Continuous monitoring using gamma spectrometers in Apatity and Barentsburg (archipelago Spitsbergen) were started in the summer-autumn period of 2009. The data is continuously, registered by the neutron 163