Ionizing particle fluxes in the near-ground atmosphere

1. Ionizing particle fluxes in the near-ground atmosphere BAZILEVSKAYA G.A., KRAINEV M.B., KVASHNIN A.N., MAKHMUTOV V.S., STOZHKOV Y.I.,SVIRZHEVSKAYA A.K., SVIRZHEVSKY N.S. Lebedev Physical Institute, RAS, Leninsky prospect, 53, 119991, Moscow, Russia

2. Motivation and goal • Ionization in the near-ground atmosphere is of interest for the cosmic ray physics and mechanisms of weather formation. • There is a discrepancy between the results of charged particle fluxes observation and simulation near the ground. • We try to understand the source of this discrepancy.

3. Long-term cosmic ray observations in the Earth’s atmosphere by Lebedev Physical Institute (Russia) • Light balloon launchings several times a week at polar (Murmansk, Arctica, and Mirny, Antarctica) and mid-latitudes (Moscow region). • Latitudinal surveys during sea expeditions. Here we use data of 1987 sea survey. • Occasional measurements with a “B1” device with high statistics at polar (Arkhangelsk region) and mid-latitudes (Saratov region). Measurements with omnidirectional Geiger tubes and with Geiger tube telescopes beginning from 1957

4. Radio-sound detectors

6. Main latitude surveys 19621965 19681969 19701971 19751976 19791980 19861987 After Golenkov, A. E., Svirzhevskaya, A. K., Svirzhevsky, N. S., and Stozhkov, Yu. I.: 1990, Proc. 21st Int. Cosmic Ray Conf., Adelaide 7, 1417.

8. L. Desorgher et al., Int.J.Mod Phys. A, 20(29),6802-6804, 2005

9. Makhmutov , 2009

10. Discrepancy between the observed and simulated particle fluxes in the near-ground level (Bazilevskaya et al., 31 ICRC, Lodz, 2009) 13-14 km Cosmic ray fluxes and CRII normalized at averages for the whole period of observations 2.3 km Cosmic ray induced ionization: Usoskin et al. Acta Geophysica, 57(1), 88-101, DOI: 10.2478/s11600-008-0019-9, 2009.

11. Assumption:Ionizing radiation in the near-ground level (below 3 km – 700 g/cm2) Cosmic rays from the atmosphere Natural radioactivity

12. Approach • A telescope is not sensitive to radioactivity. • Sea water is much less radioactive than ground or rock. • In Mirny, Antarctica, radioactivity is lower because the ground is mostly covered by glacier.

13. Data used • Data of single Geiger counters Moscow and Murmansk regions 07.1957-2010. Mirny observatory, Antarctica, 03.1963-2009. Sea survey 1987. Arkhangelsk and Saratov regions, Set of 240 Geiger counters and a NaI scintillator (1970s, Charakhchyan et al., 1975, in Russian). • Data of telescopes: Moscow and Murmansk regions, Mirny observatory, 1964-2009. Sea survey 1987.

14. It is rightful to average the data of observations at various latitudes (various geomagnetic cutoffs) over sea at atmospheric pressures >400 g/cm2 (altitude < 7 km).

19. Ratio of count rates of an omnidirectional counter and a telescope Ratio for cosmic rays

22. There is a transition effect while cosmic ray particles pass through a boundary between air and soil (rock) because differences in the critical energy for electrons in these media. • There is virtually no transition effect for cosmic rays passing from air to water.

25. Ionizing radiation in the near-ground level (below 3 km – 700 g/cm2) Cosmic rays from the atmosphere Natural radioactivity effect from the air-ground transition

26. Difference between observational data omnidirectional component) and GEANT 4 results (Desorgher et al., 2005): • Contribution from the transition effect; • Contribution from the natural radioactivity.

27. Difference between the observed X-ray fluxes at Arkhangelsk region and Mirny (Antarctida): 3. Contribution from the transition effect; 4. Contribution from the natural radioactivity.

28. Conclusion • Difference between GEANT 4 results of Desorgher et al., 2005, and results of Makhmutov, 2009 is ~ 25% - need tuning. • Divergence of results of GEANT 4 (Desorgher et al, 2005) from observations of omnidirectional fluxes of charged particles over ground begins at ~800 g/cm2 (altitude of ~2.1 km) and reaches ~30% at ~980 g/cm2 (altitude ~450 m). This is due to transition effect of cosmic rays between air and ground. • Below ~ 500 m (pressure > ~970 g/cm2) the divergence is growing due to contribution of natural radioactivity which depends on location and changes with time.

29. Conclusion (continuation) • The observational results of omnidirectional charged particle fluxes over sea surface are virtually free from the transition effect. They are in reasonable agreement with the results of GEANT 4 simulation (Desorgher et al., 2005)

30. Conclusion (continuation) • The results of X-ray observations over the ground surface demonstrate contributions from the CR transition effect (air-ground) and from natural radioactivity. • The CR transition effect should be included into GEANT 4 simulations.

31. Thank you for your attention!

33. 916 811 715 630 г/см2 Измерения сцинтил. счетчиком у берегов Австралии на самолете. 5.06.59 – после 5 дней ветра с моря, остальные дни – ветер с континента. J.A. Walburton et al., Nature, 207(4993), 181, 1965

34. Stations of the cosmic ray measurements in the atmosphere

35. The results of observations with a set of 240 Geiger tubes on the large-volume balloons (in Russian: А.Н. Чарахчьян, Г.А. Базилевская, А.Ф. Красоткин, Т.Н. Чарахчьян. Геомагнетизм и аэрономия, 15 (2), 197-202, 1975)