Events 1 Figure 4 shows Left panel ndash Negative values of the electric field and data of high energy neutrons (upper panel) thermal neutrons (lower panel) during the passage of thunderstorm cloud over the high altitude Tien Shan station

Right panel ndash Change of the electric field polarity from negative to positive data of the neutron monitor (upper panel) thermal neutrons (lower panel) The zero line - average neutron intensity before thunderstorm red line ndash values of the electric field grey line ndash 1 min data of the neutron monitor blue line - smoothed of neutron monitor data (T- 3min) green line - 1 min data of thermal neutrons

Figure 4 Values of recorded parameters during the passage of charged clouds above the station with single lightning discharges

Neutron monitor data changes occurs in opposite phase with electric field Negative values of the electric field increases the neutron monitor count rate Positive values of the electric field decreases of the neutron monitor count rate Nature of the change in the count rate of the neutron monitor depending on the polarity of the electric field suggests the muon mechanism of impact based on the catching of soft negative muons by lead nucleons with escaping neutrons It is known that 7 of the standard neutron monitor count rate caused by negative muons

Variations of thermal neutrons excluding bursts due to lightning discharges are within the standard deviation under fair weather conditions The main difference of the thermal neutrons detector from the neutron monitor consists of in the absence of the lead These results are consistent with our conclusion about the muon mechanism of the neutron monitor sensitivity to impact of electric field of the thunderstorm atmosphere in these events

Events 2 In the active phase of a thunderstorm accompanied by powerful lightning discharges in the formed thundercloud the picture of distribution of charges is complex and multilayered Results of the analysis of the count rate of neutron detectors in events 2 dont correspond to the conclusions drawn on the basis of the analysis of events 1 Values of quasistatic electric field and a high-frequency field (records the return stroke the green line) during a thunderstorm with powerful positive discharges (the left panel) are given in figure 5 The powerful discharge which gave the greatest bursts of neutrons is submitted with high time resolution

Figure 5 Values of the electric field during thunderstorm with positiv lightning discharges (left panel) the intensity of high energy neutrons (18NM64) and thermal neutrons (DTN)

Since an electrical field is usually applied in a cloudndashearth gap with minimal conductance the positive values of the surface quasistatic electrical field mean the appearance of a positive charge in the cloud slowing the negative particles (muons) moving downward Figure 5 (the right panel) shows on the contrary bursts of neutrons in all detectors The mechanism of change of the neutron flux for events 2 is different from the mechanism for events 1

Conclusions Changes of neutron flux at different stages of thunderstorm activity are caused by different mechanisms Changes of the neutron flux during thunderstorm activity without lightning discharges but with large values of the electric field is described by the mechanism of the catching of soft negative muons by lead nucleons with escaping neutrons Bursts of low-energy neutrons in the active phase of thunderstorms due to the mechanism that triggers the production of neutrons during the lightning discharge However it still is discussed The low-energy neutron flux value obtained in our work is a challenge for the photonuclear channel of neutron generation in thunderstorm the estimated value of the needed high-energy γ-ray flux is about 3 orders of magnitude higher than that one observed [6]

Introduction The question of possible generation of neutrons in a strong atmospheric electric discharge (lightning) has quite long history and can be tracked before work [1] in which possibility of acceleration of particles in electric fields of a thundercloud up to the energies sufficient for initiation of nuclear reaction is discussed During recent decades increase of neutron flux during of thunderstorm activity both in orbital experiments at sea level and in the mountains have been measured The high-altitude cosmic rays station at Tien-Shan (ge 3340 m above sea level) is a unique site for investigations of the physics of lightning discharges Installation rdquoThunderstormrdquo is designed specially for the simultaneous recording of different kinds of radiation accelerated charged particles (electrons) gamma- and X-ray radiation thermal and fast neutrons atmospheric electric fields and the radio-emission in the frequency range of 01 minus 30 MHz also as well as in VHF range about 250 MHz [2-7] The presence of a wide-spread extensive air shower trigger set-up at the Tien-Shan station permits to study the role of energetic cosmic ray particles in lightning development The aim of this paper is the study of the impact of electric fields on results of the monitoring of high-energy and thermal neutrons at different stages of thunderstorm activity

1 Experimental complex Experimental installations used in this work are part of Thunderstorm complex the standard neutron monitor (the intensity of the neutron component of cosmic rays is recorded in six energy ranges) detectors of thermal neutrons (internal and external) detector of the quasistatic electric field detector of the high frequency component of electric field The detector of the atmospheric electric field according to the principle of operation is an electrostatic fluxmeter (laquofield millraquo) designed to measure the vertical component Ez The detector was contained in a waterproof case by working plates down in order to reduce the effect of precipitation on its operation The detector allows to measure electrical fields in the range of plusmn 50kVm sampling frequency of 20 Hz under ldquofair weather conditions and of 20103 Hz under ldquothunderstorm weather conditions The high-frequency component of the electric field is recorded for the registration of the return stroke in the thunderstorm atmosphere

2 Results of the monitoring at different stages of thunderstorm activity It is known that measured variations of electric field in a surface layer of the atmosphere are caused mainly by weather conditions Variations of the electric field under fair weather conditions arent comparable with variations in the thunderstorm atmosphere Conditions of ldquofair weatherrdquo are defined according to the following criteria the absence of thunderstorms precipitation and fog visibility of more than 4 km and wind velocity of no more than 6 ms Typical diurnal values of the electric field under ldquofair weather conditions at the high altitude station for summer are presented in fig 1 (left panel) Standard deviation of minute values of the cosmic rays neutron component does not exceed 05 under ldquofair weatherrdquo conditions It is presented in all figures for data of the neutron monitor by red horizontal lines During a thunderstorm the standard deviation is always greater than that under ldquofair weatherrdquo Fig 1 (right panel)

Figure 1 Diurnal variations of electric field and data of the neutron monitor under ldquofair weather ldquo conditions (left panel) during sunderstorm activity (right panel)

Figure 2 Recordes of the neutron monitor count rate and the electric field during the passage of the thunderstorm cloud systems (without lightning discharges) consisting of multiple cells

RESPONS OF THUNDERSTORM ACTIVITY IN DATA OF NEUTRON MONITORING AT TIEN-SHAN STATION

Valentina Antonova Sergey Kryukov and Vadim LutsenkoInstitute of Ionosphere of the National Center for Space Research and Technology Almaty Kazakhstan

E-mail valantaramblerru

Study of similar thunderstorm events at Tien Shan has shown that a change in the count rate of the standard neutron monitor occurs at values of electric field ge 10divide 15 kV m Fig 2 The intensity of the neutron component of cosmic rays is recorded in six energy ranges (200 MeV divide 30 GeV) It has been established experimentally that the sensitivity of the detected particles to a changes in the electric field Ez increases with decreasing their energy The response to the impact of the electric fields is absent in channels for neutron multiplicity ge6 that corresponds to the energy of particles ge 10 GeV Fig 3

References [1] CTRWilsonProceedings of Cambridge Phylosophycal S0city 22534-538 1924[2] A V Gurevich A N Karashtin et al Physics Letters A 325389-402 5 2004 [3] A P Chubenko et al Physics Letters A 373(39)2953-2958 6 2009 [4] A V Gurevich et al Physics Letters A 373(39)3550-3553 9 2009 [5] V P Antonova et al Radiophysics and Quantum Electronics 52(9)627-640 2009 [6] A V Gurevich V P Antonova A P Chubenko A N Karashtin et al Physical Review Letters 108125001-4 3 2012 [7] A V Gurevich V P Antonova A P Chubenko A N Karashtin et al Physical Review Letters 111165001 10 2013

We divided the results of monitoring high-energy neutrons (the neutron intensity measured by a standard monitor 18NM64) and thermal neutrons during the passage of thunderstorm clouds above the station depending on the stage of thunderstorm activityEvents 1 - The intensity of neutrons of different energies during the passage of thunderstorm clouds above the station without lightning discharges In these events change in the intensity of the particles is determined only by the electric field due to the charge distribution in the thundercloud and the earths surface Figure 4Events 2 - The intensity of neutrons of various energies during the passage of thunderstorm clouds over the station in the active stage of thunderstorm accompanied by powerful lightning discharges The generation of neutrons is possible in these events

Figure 3 Variations of the neutron intensity in six energy ranges for the 2nd event of Fig 4(the vertical dotted line is the instant at which the electric field polarity changes from negative to positive)

• Slide 1