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Solar Modulation: A Theoretical Perspective

Solar Modulation: A Theoretical Perspective Modeling of cosmic ray charge-sign dependence in the heliosphere. Marius Potgieter Unit for Space Physics North-West University Potchefstroom, South Africa. Colaborators: Stefan Ferreira, Bernd Heber

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Solar Modulation: A Theoretical Perspective

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  1. Solar Modulation: A Theoretical Perspective Modeling of cosmic ray charge-sign dependence in the heliosphere Marius Potgieter Unit for Space Physics North-West University Potchefstroom, South Africa Colaborators: Stefan Ferreira, Bernd Heber Students: DuToit Strauss, Etienne Vos, Driaan Bisschoff, Rex Manuel, Edwin Mogadimisha PAMELA Workshop May 2009

  2. Cosmic Rays from the Galaxy Charged Particle Populations Inside the heliosphere

  3. Heliospace 500 AU Voyager 1: Dec 2004 250 AU Bow Shocks Voyager 2: Aug 2007 The heliosphere

  4. Hydrodynamic part A 5 fluid model based on the Kausch (1998) model : > mass density , velocity u, pressure P and Q sources related to the interaction between the various species. > describe the balance of mass, momentum and energy of the protons in solar wind and LISM, neutral hydrogen, pickup ions, and additional is GCR’s and ACR’s Realistic heliospheric geometry and solar wind flow profile Magnetic part > Magnetized flow is calculated by solving Faraday’s law assuming ideal MHD Magnetic field Cosmic ray transport part Cosmic ray transport and acceleration calculated by Parker (1965) TPE : > including all major modulation mechanisms : diffusion, drifts, convection and energy changes

  5. How is the heliosphere formed ? Allow the physics to tell us !

  6. Hydrodynamic modeling of major heliospheric structures HP 245 AU HP 140 AU TS 93AU TS 155 AU Scherer, K., & Ferreira, S. E. S. 2005, ASTRA, 1, 17 TS 205 AU Ferreira, S. E. S., & Scherer, K. 2004, ApJ, 616, 1215

  7. Termination shock changes position over a solar cycle Predictions of TS crossing for V1 and V2 V1 & V2 launched in 1977 AU V1 is presently at 107 AU, 34°N r V2 is presently at 86 AU, 28°S Time (years) V1 crossed the TS in Dec. 2004 at 94 AU V2 crossed the TS end of Aug. 2007 at 84 AU

  8. Cosmic rays are excellent indicators of solar cycle variations Modulation of galactic cosmic rays at Neutron Monitor energies

  9. Modulation-Acceleration Model Transport equation for the modulation and acceleration of cosmic rays in the heliosphere Time-dependent, pitch-angle-averaged distribution function Diffusion Convection with solar wind Particle Drifts Adiabatic energy changes Any local source Second order Fermi acceleration Parker (Planet. Space Science, 13, 9,1965)

  10. Heliospheric CR Modulation Processes As for electrons

  11. Heliosphere & Cosmic Ray Modulation Mechanisms The wavy current sheet (HCS)

  12. The wavy heliospheric current sheet (HCS) Extreme solar activity Maximum solar activity Moderate solar activity Minimum solar activity Tilt angle of the HCS: proxy for solar activity

  13. Computed Galactic Spectra (LIS?) Moskalenko and Strong, 2002. Langner, 2002, 2005;

  14. Solar modulation of galactic carbon Webber et al. (AIP-IGPP-2006)

  15. Major features of cosmic rays near Earth Observed spectra crossings at Earth, from A > 0 and A < 0 solar minima polarity cycles… Observed small latitudinal gradients, especially at low energies; compared to Ulysses-KET observations; for A > 0, solar minimum to maximum… Langner, Potgieter & Webber, JGR, 2003; ASR, 2004

  16. Effects of gradient and curvature drifts in the heliosheath-nose 200 MeV GCR protons Solar minimum conditions Conclusions: GC&CS-drifts may play a significant role in the HS….? Without drifts the TS seems insignificant for GCRs … The HP is more important to GCR modulation than the TS Langner, Potgieter & Webber, JGR, 2003

  17. Drifts during a complete solar activity cycle

  18. Long term modulation: charge-sign dependence Long-term modulation of 1.2 GV electrons and helium at Earth over 22 years. Electron measurements form ISEE/ICE (Clem et al., 1996; Evenson, 1998). He measurements form IMP (McDonald, 1998; McDonald et al., 2001).

  19. Computed radial gradients for galactic protons At Earth During solar minimum modulation; A > 0; A < 0 50 AU TS = 91 AU

  20. Computed proton polar gradients Earth During solar minimum modulation; A > 0; A < 0 50 AU 91 AU

  21. Modulation of galactic protons and anti-protons at solar minimum

  22. Modulation of galactic electrons and positrons at solar minimum

  23. Ratio of Electrons to Positrons At Earth Solar minimum modulation Two concecutive magnetic field polarities Ratio of Electrons to Positrons At Earth Solar maximum modulation Two concecutive magnetic field polarities

  24. Ratio of Electrons to Positrons At Earth vs. LIS Solar minimum modulation Two concecutive magnetic field polarities Ratio of Protons to Anti-protons At Earth vs. LIS Solar minimum modulation Two concecutive magnetic field polarities

  25. The Wonders of Heliospace Profile of the Latitudinal Solar Wind

  26. Electron Spectra at Earth and at increasing radial distances Contribution of Jovian Electrons

  27. Modulation of Jovian ElectronsJupiter is a strong source of low-energy electronsat 5 AU Illustration of electrons following the HMF spiral structure; paralllel and perpendicular diffusion

  28. Charged-sign Dependent Modulation over two Solar Maxima Electron measurements form ISEE/ICE (Clem et al., 1996; Evenson, 1998) and KET (Heber et al, this conference). He measurements from IMP (McDonald, 1998; McDonald et al., 2001).

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