1. Precursor signatures of storm sudden commencement observed by a network of muon detectors C. R. BRAGA 1, A. DAL LAGO 1, M. ROCKENBACH 2, N. J. SCHUCH 3, L. R. VIEIRA 1, K. MUNAKATA 4, C. KATO 4, T. KUWABARA 5, P. A. EVENSON 5, J. W. BIEBER 5, M. TOKUMARU 6, M. L. DULDIG 7, J. E. HUMBLE 7, I. S. SABBAH 8, H. K. AL JASSAR 9, M. M. SHARMA 9 1 National Institute for Space Research, São Jose dos Campos, Brazil 2 Universidade do Vale do Paraíba,São Jose dos Campos, Brazil 3 Southern Regional Space Research Center, Santa Maria, Brazil 4 Physics Department, Shinshu University, Matsumoto, Japan 5 Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, USA 6 Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, Japan 7 School of Mathematics and Physics, University of Tasmania, Tasmania, Australia 8 Department of Natural Sciences, College of Health Sciences, the Public Authority of Applied Education and Training, Kuwait - Department of Physics, Faculty of Science, Alexandria University, Alexandria, Egypt 9 Physics Department, Faculty of Science, Kuwait University, Kuwait City, Kuwait E-mail: crbraga@dge.inpe.br

2. 2 Detectors photographs (except Sao Martinho da Serra): private communication with Prof. K. Munakata, 2010 and Prof. I. Sabbah, 2011 Background source: http://earthsatellitemaps.com/wp-content/uploads/2009/06/mapofearth.jpg, 2010http://earthsatellitemaps.com/wp-content/uploads/2009/06/mapofearth.jpg Global Muon Detector Network (GMDN) São Martinho da Serra Kuwait Hobart Nagoya 4 x 7 6 x 6 3 x 3 (4 x 4) 3 x 3

4. Source: Yashin et al. (2006).

5. Methodology - Pressure effect correction; - Temperature effect correction; - Trailing moving average; - First order anisotropy; - Normalization by statistical error. Objective To study the possibility of observing cosmic ray precursors of a weak geomagnetic storm registered in November 24th 2008 with storm sudden commencement (SSC) at 23:51 UT.

6. Negative temperature effect ∆H: deviation of the altitude of 100 hPa Correlation=-0.95 Dev(%)=-5.9 (%/km) ∙ ∆H (km) + 97% Deviation Na V(%) Altitude (km) of 100 hPa layer

7. Temperature effect correction Correlation=-0.95 Nagoya: α≥ 0.95 -6.7 ≤ β ≤ -5.9 %/km São Martinho da Serra : α≥ 0.49 -4.8 ≤ β ≤ -3.7 %/km Hobart: α≥ 0.72 -5.0 ≤ β ≤ -3.6 %/km Kuwait: α≥ 0.89 -7.3 ≤ β ≤ -6.1 %/km Dev(%)=-5.9 (%/km) ∙ ∆H (km) + 97% Deviation Na V(%) Altitude (km) of 100 hPa layer β: regression coefficient (slope) α: correlation coefficient

8. High-altitude measurements sites High-altitude pressure measurements sites Muon station Approx. distance (km) Name Geographic coordinates (degrees) Shionomisaki33.5 N; 140.1 E Nagoya 200 Tateno36.0 N;140.1 E400 Wajina37.4 N; 136.9 E300 Porto Alegre30.0 S; 308.8 ESão Martinho da Serra260 Kuwait29.2 N; 48.0 EKuwait10 Hobart42.8 S; 147.5 EHobart30

9. Day of year (2008) Seasonal temperature effect correction Kuwait Dev (%) Nagoya Dev V(%) Hobart Dev V(%) SMS Dev V(%) NORTH HEMISPHERE SOUTH HEMISPHERE SUMMERWINTER SUMMERWINTER SUMMER WINTER

10. Trailing moving average (TMA) TMA of the reference directional channel (i=1) of the reference station (j=1) Uncorrected data Corrected data Directional Channel Station 10 Removing spurious diurnal variation (following Kuwabara et al., 2004; Okazaki et al., 2008)

11. Pitch angle calculation Pitch angle IMF direction SUN B Asymptotic direction of view of the i-th directional channel of the j-th station EARTH 11

12. First order anisotropy Nagoya (i=1, j=1,2,…,13) São Martinho (i=2, j=1,2,…,13 Kuwait (i=3, j=1,2,…,13 Hobart (i=4, j=1,2,…,13 52x1 52x5 5x1 : observed normalized deviation i є [1,4] (detector) j є [1,13] (directional channel) : effects common for all directional channels but different from one station to the other : first-order anisotropy : pitch angle (deg)

13. Results Systematic decrease for small pitch angles: loss cone signature! The diameter is proportional to the magnitude. IncreaseDecrease SSC: 2011/11/24 23h51min 0.3%

14. Average deviation (%) Results 1-6 h before the SSC 6-11 h before the SSC 11-16 h before the SSC 16-21 h before the SSC Average deviation (%) for all directional channels in 10-degree pitch angle regions in 5-hour periods in November 24 th 2008.

15. Summary and conclusions This work illustrates a methodology for visualization of loss cones signatures We used simultaneous observation of 4 multidirectional muon detectors; Total number of directional channels: 60; Pressure and temperature effect were removed; Daily variation was removed by using a trailing moving average; Weak geomagnetic storm: the most difficult case to show the precursors.

16. Acknowledgements This work was partially founded by FAPESP under project number 2008-08840-0, by CNPq under projects 303798/2008-4 and 481368/2010-8. Thanks to CAPES through the Graduate Program in Space Geophysics. Radiosonde data has been provided by UKMO and BADC. Dst index data were provided by the World Data Center for Geomagnetism, IMF and plasma data by the ACE mission and Kp and SSC data by the Helmholtz Centre Potsdam German Research Centre for Geosciences. References [1] T. Kuwabara et al., 2006, Space Weather, 4, S08001 [2] D. Ruffolo et al., 1999, Proceedings of the 26 th Int. Cosmic Ray Conf., 53. [3] L. I. Dorman: 1963 Geophysical and Astrophysical Aspects of Cosmic Rays, Prog. Phys., Cosmic Ray Elementary Particles, North-Holland. [4] K. Nagashima et al., 1992, Planet. Space Sci., 40: 1109-1137 [5] K. Munakata et al., 2000, J. Geophys. Res., 105 (A12): 27427-27468 [6] K. Kudela; M. Storini, 2006, Adv. Space Res., 37(8): 1443-1449 [7] A. V. Belov et al., 2001, Proceedings of the 27 th Int. Cosmic Ray Conf., 3507-3510 [8] Y. Okazaki et al., 2008, Astrophys. J., 681: 693-707 [9] A. Duperier, 1944, Terrestrial and Magnetic Atmospheric Electricity, 49: 1-7 [10] A. Duperier, 1949, Proceddings of the Physical Society, 62: 684-696 [11] P. M. S. Blackett, 1938, Phys. Rev. Let. 54: 973-974 [12] S. Sagisaka, 1986, Il Nuovo Cimento, 9C: 4809 [13] T. Kuwabara et al., 2004, J. Geophys. Res., 100: L19803. Thank you!

17. Pressure effect correction Pressure correction

18. First order anisotropy SSC: 2011/11/24 23h51min