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. Continuous monitoring using gamma spectrometers in Apatity and Barentsburg were started in the summer-autumn period of 2009. During the observations we detected sporadic increases in the intensity of X-ray radiation. It was also noted that the increase events almost always were accompanied by intense precipitations, with dense and low altitude (200-600 meters) cloudiness, so called “nimbostratus clouds”, data on [] . Figure 1 shows typical profiles of the count rate increase in the X-ray channel > 20keV ^nd precipitations for the Apatity and Barentsburg stations. The good correlation between the strengthening of rain and increases of the X-ray intensity in Apatity is seen in Figure la. Similarly, the good correlation is observed between the X-ray increase and snowfall in Apatity, Figure lb. Curve 3 is the data of Geiger telescope channel which shows no any increase. It can specify lack of charged particles in the event, connected to precipitations. There were observed over 280 X-ray increase events from June 2009 to June 2011. The intensity increased up to 50% of the background and duration of an increase varied from one hour to two days. 97% of these events were accompanied by precipitations of varying duration and intensity. The amplitude of increases differs for different seasons. In winter the amplitude of increases was on the average less and there was not fixed any increase greater than 30%. 3. Observations 10 August 2009 si a i/i я <uuиe 221.00 221,25 221,50 221,75 431,25 431,50 431,75 432,00 Day o f ye a r D a y o f yea r F ig .l. Typical events of X-ray increases (1) related to precipitations (2). a) rainfall event of 10.08.2009 in Apatity; b) snowfall event of 8.03.2010 in Apatity, 3 is the G-M telescope channel. In addition, the connection of the type of precipitation with the increase amplitude was noted. Fine, dry snow with the wind (blizzard) or permanent drizzling rain rarely was accompanied with an increase. Most of the increase events were accompanied by heavy rains or snowfall with no strong wind. During 2010 in Apatity only 3 thunder-storms in the summer season were observed. Increases of photons in these thunder-storms were small, < 5-10 %, that is quite low for the summer season. The low bound of cumulus clouds in these thunder-storms exceeded 1000 m ( 122/ru), that we consider a reason, why X-ray increases were so small. 4. Check experiments For clearing up the nature of increases observed on detectors Nal(Tl) it was required to carry out a series of additional check experiments. In particular, lack of radioactivity in precipitations (rain and snow) during observation of increases has been proved. For check of connection of effect described here with a radio-activity of atmospheric precipitations we have used the data of the regional laboratory of radiochemical control. This laboratory carries out regular measurements for the last few years. Weekly samples of precipitations (all amount of precipitation, collected for the last week) are analyzed. We compared the weekly records of radioactivity in precipitations in Apatity with increases on our gamma-spectrometer. There is no regular connection of occasional radioactivity enhancements with increase events detected by our gamma-spectrometer and which we attributed to the X-ray bremsstrahlung events. In several cases of considerable X-ray increases the samples of precipitations in the form of rain and snow have been collected and analyzed with radiochemical methods. The radiometric analysis o f these samples showed no excess over the background level of beta and alpha activity. The gamma-spectrometric analysis has shown usual presence of the natural radio nuclides which activity does not exceed the background level observed before and after an event. Also lack of effect of radium emanation on observed X-ray radiation has been shown. It is known, for example, that rain scavenges radon progenies efficiently and it emits gamma radiation in the energy range of hundreds keV. Increases of X-rays during precipitations in the winter season are observed with the same effectiveness as in the 186