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Quiet-time proton fluxes in the streamer belt: information from Ulysses

Quiet-time proton fluxes in the streamer belt: information from Ulysses. K. Kecskeméty KFKI Research Inst. for Particle and Nuclear Physics, Budapest, Hungary Yu.I. Logachev, M.A. Zeldovich Skobeltsyn Institute of Nuclear Physics, Moscow State University, Russia.

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Quiet-time proton fluxes in the streamer belt: information from Ulysses

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  1. Quiet-time proton fluxes in the streamer belt: information from Ulysses K. Kecskeméty KFKI Research Inst. for Particle and Nuclear Physics, Budapest, Hungary Yu.I.Logachev, M.A. Zeldovich Skobeltsyn Institute of Nuclear Physics, Moscow State University, Russia 21stECRS, Košice, 11 September 2008

  2. Energy spectrum Suprathermal and energetic ions ~100 keV - ~30 MeV: always present in interplanetary space, power-law tail of Maxwellian, pick-up from Mewaldt et al. (2001)

  3. Experimental difficulties very low fluxes/small detectors instrumental background + energy misidentification ~2-10 MeV 2 detectors/PHA >10-20 MeV – galactic/anomalous contribution Data sets used twofold coincidences, dE/dx vs. E technique, PHA analysis instrumental background determined with the same method as for other detectors (SOHO EPHIN) Ulysses COSPIN/LET (1.8-8.1 MeV) R= 1 - 5.4 AU solar activity minima 1994-1997 and 2006-2007 fast latitude scan transient events removed, only the quietest periods analyzed

  4. Radial variation 0.3 - 85 AU

  5. Ulysses: variation with radial distance

  6. Latitudinal variation

  7. 1994-97 + 2006-07 quiet periods

  8. Variation along the orbit

  9. Conclusions Radial variation Ulysses 2-8 MeV quiet fluxes are lower by ~5 to 10 than at Helios and Voyager, but only by ~2 lower than at Earth  probably only partially due to a latitude effect Latitudinal distribution Lowest fluxes are 20-30 times lower beyond the streamer Pedestal between 45S and 30N Favours interplanetary/CIR origin vs solar/microflare Asymmetry: gradual increase in northern hemisphere abrupt change in southern hemisphere Relation to the southward drift of heliospheric current sheet? (Mursula and Hiltula, 2003)

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