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Galactic and Anomalous C osmic R a ys in the Heliosheath

● V-1. 21 st ECRS, Ko šic e, September 2008. ● V-2. Galactic and Anomalous C osmic R a ys in the Heliosheath. J ózsef K ό ta University of Arizona Tucson, AZ 85721-0092, USA Thanks to : J.R. Jokipii, J. Giacalone. kota@lpl.arizona.edu.

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Galactic and Anomalous C osmic R a ys in the Heliosheath

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  1. ● V-1 21st ECRS, Košice, September 2008 ● V-2 Galactic and Anomalous Cosmic Rays in the Heliosheath József Kόta University of Arizona Tucson, AZ 85721-0092, USA Thanks to : J.R. Jokipii, J. Giacalone kota@lpl.arizona.edu

  2. Motivation: where is the source?is history repeating itself ?? ACR fluxes continued to increase beyond TS Source outside Shock V. Hess 1912 Voyager-1 December 2004 Similar result from V-2 (2007)

  3. ● Are Anomalous Cosmic Rays (ACRs) indeed accelerated at the solar wind termination shock (TS) ? Likely yes but ● Bluntness of TS counts ● Topology between Shock & Field lines counts

  4. Heliosphere: our cosmic environment < 1000 AU (10 lightdays) > Pristine ISM ● V1 TS Solar material Perturbed ISM 26 km/s

  5. Global structure of Heliosphere VLISM: partially ionized H,He 0.1/cc μG B ? ACR SEP GCR

  6. ACRs are accelerated at the solar wind Termination ShockSame Physics as SNR ACRs SNR Diffusive Shock Acceleration: 1st order Fermi Energy gain from crossing the shock many times

  7. LECP Low energy charged particles (Decker JHU-APL)

  8. Voyager-1 after crossing the TS ACR fluxes continued to increase into the Heliosheath ● Temporal variaton (Florinski Zank,2006) ● Magnetic topology (McComas & Schwadron, Kόta & Jokipii) ● Combination of the two?

  9. First Signature of Blunt Shock • Voyager-1 observed large beaming anisotropies seemingly from the sunward direction. • Interpreted in terms of multiple intersection between the Parker spiral field and the blunt TS • Hint for a deformation of the shock (likely due to interstellar B).

  10. How do we understand “anti-sunward” anisotropies?Magnetic field line may intersect the TS multiple times. Jokipii, Giacalone, and Kota 2004, Kóta and Jokipii 2004 Multiple intersection also explains the two population spectrum V-2 V-1 Displacement of the ‘nose’ helps

  11. McComas and Schwadron (2006) Blunt Shock: acceleration at Flanks ? Short time for acceleration

  12. Topological effects on ACR spectrum • Acceleration ineffective at the nose due to lack of time fof acceleration. • ACR spectrum does not unfold at the TS • ACR flux continues to increase into the heliosheath • Could have been anticipated

  13. 2-D Model: TS = Offset Circle • In the modeling we select an offset sphere for the TS Another possibility is bullet shape (McComas & Schwadron, 2006) • Nose region (V1 and V2) is similar in either case • Differences can be expected for the tail region. Tail region turn effective for sphere and probably less effective for bullet shape. • Consider preferential injection at flanks

  14. Blunt Shock (offset circle)perpendicular diffusion included (η=0.02) Polar contours of simulated 200keV fluxes & spectrum along the TS

  15. 2-DSimulation – Blunt shock Model: 2-D plane, TS offset circle, uniform injection at 10 keV, η=0.02 V-2 Radial variation at fixed azimuth: fluxes continue increase beyond TS V2 V1 V-1

  16. Larger perpendicular diffusion: η=0.05 effect smaller but still there

  17. Summary: ●V-1 ●V-2 ● Magnetic field lines cross the blunt TS multiple times. This explains: ● Upstream field-aligned anisotropies - away from the Sun (V-1) – TS offset helps - toward the Sun (V-2) if TS is offset ● Two-population spectrum: low energy particles are accelerated at nearby “fresh” shock. ACRs are accelerated farther away are still modulated at the TS, and continue to increase into the heliosheath. ● 2-D Shock differs from 1-D shock (topology) Think in 2 D (at least) ● Topology may be important at other shocks too.

  18. Motto: ● “Make everything as simple as possible, but not simpler “ “Topology counts”

  19. Voyager-1 in the Heliosheath ● V-1 crossed the Termination Shock on December 16, 2004 After Crossing: ●small anisotropies ● small day-to-day variability ● ACRs still modulated ● Double power law spectra with break around few MeV/n (He:H=1:10) Before Crossing: ● large beaming anisotropies from sunward direction ● large day-to-day variability ● ACRs still modulated – two-population!? ● Voyager-2 crossed the TS on DOY 244, 2007

  20. Voyager -1 & -2 reached the TS 2004/2007 SW Plasma LECP CRS radio Launched in 1977 B Interestingly in the same year as the theory of shock acceleration

  21. Where is the Termination Shock ? Very different methods all predict ~100 AU range Shock is not steady but moves in response of solar input E.C. Stone 2001

  22. Uneven injection: preferential injection at flanks Injection at 10 keV, q~sin(θ)**2

  23. Preferential injection at flanks contn’d

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