The heliosphere and galactic cosmic rays: modulation, Forbush decreases

1. The heliosphere and galactic cosmic rays: modulation, Forbush decreases Belov IZMIRAN, Russia Athens, September 2009

2. Neutron monitors?Why? Jungfraujoch, Switzerland Lomnicky Stit, Slovakia

3. Welcome to research with us. • Our preferences: • worldwide neutron monitor network (created by Simpson); • system of the atmosphere-magnetosphere filtration and particle separation by energies (created by the Creator); • support from ionization chambers, muon detectors, stratosphere and satellite measurements; • stable conditions: a constant distance from the Sun and a narrow heliolatitude range; • engaged and qualified society • and much more

4. Construction of NM network

5. All neutron monitors John Simpson

6. Spectrum of galactic cosmic rays.Modulation.

7. Long-term cosmic ray variations.Modulation. Long-term CR variations (1953-2009)recorded by the Climax and Moscow neutron monitors.

8. Other CR measurements Long-term CR variations (1936-1998 years) recorded on ionization chambers

9. Other CR measurements Long-term CR variations (1957-1997 years)recorded in stratosphere (Bazilevskaya and Svirzevskaya, 1998) and by IMP-8 satellite (ftp://odysseus.uchicago.edu/WWW/Simpson/Imp8.html).

10. Heliosphereis huge

12. Modulating parametersHCS tilt, and mean solar magnetic field

13. Cosmic rays and Heliospheric Current Sheet (HCS) tilt Cosmic rays and Heliospheric Current Sheet (HCS) tilt 2002 - 2007 1982 - 1987

14. What creates CR modulation? Convection CR Scattering

15. What creates CR modulation? Sun, cosmic rays and mediators

16. Histeresis Cosmic ray dependence on sunspot number for 4 successive solar cycles.Interchange of broad and narrow hysteresis loops.

17. Histeresis – memory of heliosphere Relation of the 36-month running averaged cosmic ray variationsand sunspot numbers for one solar magnetic cycle. Nagashima and Morishita (1980) gave a simple explanation for this interchange. It is enough to admit that the CR intensity near the Earth on the whole is higher under the negative polarity. Then, if the solar activity – cosmic ray relation does not differ very much for the different polarities, the (+/-) transition shall broaden the hysteresis and (-/+) transition shall get it narrow.

18. Rigidity spectrum of long term CR variation Observed by neutron monitors and IMP-8 cosmic ray variations (January 1993 relative to 1996) versus the calculated variation for the simplest (R-1) spectrum On Figure, related to January 1993, data from NMs and from highest energy channel (>106 MeV) of IMP-8 are in excellent agreement as one with another so with the simplest model, where the primary variation is inverse related to rigidity. Such an agreement was observed not only on this month, but also from middle of 1992 to solar activity minimum (and base period) on 1996. Similar picture was emerged in the other cycles. So, along of many-year periods within the wide (two-three orders) rigidity range a primary CR variation can ideally suite to the simple power dependence close to R-1. But growth of solar activity and reversals of polarity destroy completely this simplicity.

19. Periodicity of modulation

20. Heliolatitudinal distribution of GCR 1994-1996 1998-2001 Meridional cut of the >2 GeV/n protons spatial distribution in a sphere of 5 AUduring solar minimum and solar maximum.Dark and light regions correspond to low and high intensities, respectively.

21. Cosmic ray anisotropy5 solar activity cycles, 3 solar magnetic cycles,442 704 arrows

22. >70 years,7 solar cyclesfrom Forbush effect discovery Forbush, S. E.: 1937, 'On the Effects in the Cosmic-Ray Intensity Observed During the Recent Magnetic Storm', Phys. Rev.51, 1108–1109. Forbush, S. E.: 1938, 'On the World-Wide Changes in Cosmic-Ray Intensity', Phys. Rev.54, 975. Lockwood, J. A.: 1971, 'Forbush Decreases in the Cosmic Radiation', Space Sci. Revs.12, 658–715. Cane H.V.,2000, CMEs and Forbush Decreases, in: ISSI Space Science Series, 10, “Cosmic Rays and Earth” Dorman L.I.

23. Database of Forbush effectsand interplanetary disturbances Cosmic ray charachteristics (10 GV rigidity), from world network of neutron monitors ~5900 events for 1957-2006

24. What is Forbush effect? Cosmic ray variation during the geomagnetic storm (from old textbooks) FORBUSH DECREASE. An abrupt decrease, of at least 10%, of the background galactic cosmic ray intensity as observed by neutron monitors. ON-LINE GLOSSARY OF SOLAR-TERRESTRIAL TERMS (NOAA)

25. What is Forbush effect? Variation of the background cosmic rays due to solar wind disturbances generated by CME and/or coronal hole

26. CMEs and Forbush decreases Cosmic ray decrease is created by expansion of disturbed region that partly screened from outside by strong and/or transverse magnetic fields Expansion and limited exchange

27. Coronal holes and Forbush decreases Other mechanism but similar result sometime.

28. Coronal hole effect Giant coronal hole in March 2003 and its influence on solar wind, cosmic rays and geomagnetic activity

29. Forbush decrease isthe largest galactic CR variation 23thcycle The largest FE in the last cycle and in history and full 11-year CR modulation in the same scale.

30. Size distributions of FEs

31. What is the big Forbush effect? minor strong extreme Comparing of FE and geomagnetic storm rates

32. Forbush effect is the most variable effect

33. The elephant and blind mens

34. Forbush effect is the most variable effect

35. Forbush effect – heliospheric phenomenon Forbush effect in September 1959 as it was observed from different directions

36. History of Forbush Effects >=15%

37. History of FEs. Cycle of solar activity. Monthly and yearly mean Forbush-effects magnitudes

38. History of FEs

39. Forbush effect seriesMarch-April 2001

40. Solar acivity burst index, combined fromX-ray flare and Forbush effect data Averaged burst probability along cycle of solar activity

41. Burst probability forecast Changes of burst probability in 3 last solar cycles and forecast for the next cycle

42. Forbush effect is the most anisotropic effect February 1978 Sometimes in Forbush decrease anisotropy of galactic CR go up to 10 % (20 times bigger than normal). In this example we saw also ~10 % second harmonic of anisotropy, that 2 orders higher usual values.

43. Anisotropy of FD. February 1978.

44. Cosmic ray anisotropy5 solar activity cycles, 2+ solar magnetic cycles,433 944 arrows

45. CR anisotropy in Forbush effects Abrupt changes of magnitude and direction of anisotropy near IP shock and in minimum of FD (abrupt change of CR gradient).

46. CR anisotropy in Forbush effects. Magnetic clouds. MC Example of complex behavior of CR anisotropy inside FE

47. CR anisotropy and gradient in Forbush effects Sometimes CR gradient in the period of large FE >100 %/a.e. Mostly across IMF.

48. Anisotropy. FD without D

49. Anisotropy. FD without D Sudden turn of CR anisotropy vector in the moment of shock arrival

50. FD. CR anisotropy. 2nd harmonic. Magnetic cloud. Variation of 10 GV cosmic ray flux and the amplitude of second order anisotropy during a Forbush-decrease in September 1978 presented together with solar wind speed Vsw, intensity (B) and BZ -component of IMF. REFF – effective rigidity used for calculating the second spherical harmonic Several tens of examples in (Richardson, Dvornikov, Sdobnov and Cane.: 2000).