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Energy spectra of suprathermal and energetic ions at low solar activity

Károly Kecskeméty Wigner Research Centre for Physics, Budapest, Hungary. Energy spectra of suprathermal and energetic ions at low solar activity. 23rd European Cosmic Ray Symposium, Moscow, 5 July 2012. Outline. e nergy spectra suprathermal 100 keV -1 MeV energetic 1-30 MeV

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Energy spectra of suprathermal and energetic ions at low solar activity

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  1. KárolyKecskeméty Wigner Research Centre for Physics, Budapest, Hungary Energy spectra of suprathermal and energetic ions at low solar activity 23rd European Cosmic Ray Symposium, Moscow, 5 July 2012

  2. Outline • energy spectra • suprathermal 100 keV-1 MeV • energetic 1-30 MeV • variability, quiet-time periods • protons, radial variation: Helios, 1 AU, Ulysses, Voyager • latitude variation: Ulysses • 3He, heavy nuclei 1-30 MeV/n • populations, acceleration mechanisms • future prospects

  3. Energetic charged particles measurement: counting rates m,Z,q (E,r,,,t) fZ,m,q (x, v, t) differential fluxphase space densitym,Z elemental/isotopic compositionq charge state composition E energy spectrum r, heliocentric radial and latitudinal variationmpitch angle distribution/anisotropy tshort-term: transients, fluctuationslong-term: solar cycle, 22-year

  4. Cosmic ray energy spectrum

  5. Ionpopulations in the Heliosphere Gloeckler (2008)

  6. Fluence spectrum Mewaldt et al. (2007)

  7. Variability solar/interplanetary activity: fluctuating process high fluxes – localized source, low fluxes - global • solar wind proton flux density: 2x108 /cm2s (high-speed) 4x108 /cm2s (low-speed, Wang, 2010) • suprathermals: ~100 • 1-10 MeV >107 • 100 MeV ~103 • 1 GeV (galactic) factor of <2 (Feldman et al, 1978) ~3 GeV

  8. Variability (100 keV-100 MeV) Gloeckler & Fisk (2006)

  9. Questions, problems • Does a quiet Sun exist? • Which populations are present during quiet times? • How their contribution vary throughout the Heliosphere? • Do they exhibit a 11/22 year variation? • What are the element composition/ionization states? • What are the seed populations of energetic particles? • What is the source of suprathermal ions: continuous solar emission (micro/nano/pico SEP) or CIRs? • Suprathermals at <1 AU? • Heavy ion populations at quiet times (suprathermal + energetic) • Origin of 3He (present for extended time periods)

  10. Quiet time periods • Definition: - ”no event” (depends on solar activity) • - low particle flux (depends on energy) • - low fluctuation level • background problem: pulse-height analysis needed  • difficult at <1 MeV, small geometry factor  • poor statistics at >1 MeV IMP-8 protons (1-25 MeV)

  11. Particle sources at quiet times accelerated solar wind(suprathermalions) SEP eventremnants micro-/nano-/picoSEP events CIRs/GMIRs (backstreaming at <1 AU) interplanetary shocks turbulence magnetospheric – cometary ions ionizedneutralspick-up anomalous component, TSP

  12. Suprathermal energies solar wind plasma: in turbulent quasi-equilibrium Lorentziank-distribution superhalo: Lin (1998) Gloeckler (2003) up to 100 keV/n pickup: comets, dust, outer sources 1 AU Mason & Gloeckler (2011) ACE, Ulysses: universal spectrum f ~ v-5 J ~ E-1,5 up to ~150 keV particular case of k-distribution seed population for energetic particles

  13. Very quiet periods spectral slope: steepening at >300 keV/n protons -2.7 in 1977 -2.1 in 2007-09 4He -2.6 in 1977 -2.6 to 2.0 in 2007-09 composition: CIR-like 2007-09 1977 Mason & Gloeckler (2011)

  14. Interplanetary acceleration - models • Fisk & Lee (1980): CIR acceleration beyond 1 AU and transport back to 1 AU – shock compression ratio? upstream propagation at 100 keV? • Giacalone et al (2002): acceleration in compression regions • Fisk & Gloeckler (2006) acceleration from stationary isotropic turbulence reproduces the E-1.5 spectral tail (particular case of k-distribution) • Drake et al (2010): magnetic reconnection – also E-1.5 Mason &Gloeckler (2011)

  15. Spectral minimum: 1-30 MeV (1 AU) large fluctuations background (instrumental, neutrals, high-energy?) small size detectors  poor statistics <1 proton/day 1996 fluxes are lower at negative magnetic polarity (qA < 0, 1986) Logachev et al (2002)

  16. Protons at 1 AU IMP-8 energy spectrum: good fit with sum oftwo populations J(E) =AE-g+ CE-n solar/heliospheric galactic spectral parameters obtained from best fits to spectra • 1.3 for protons (force-field n = 1) Kecskeméty et al (2011) Gomez et al (2000)

  17. Variation of spectral parameters with solar activity minimum: SH moves downwards, galacticupwards  Emin is shifted to lower energies IMP-8,Logachev et al. (2002)

  18. Radial and latitude variation • Observations: use similar instrumentation - semiconductor telescopes • 1-30 MeV, same background reduction method (PHA) • IMP-8 CPME, EIS, CRNC 1 AU • SOHO ERNE, EPHIN 1 AU • Helios 1-2 Kiel exp 0.29-0.98 AU • Ulysses LET 1.4-5.4 AU, -80 to +80 • Voyager 1-2 CRS 1-85 AU, -25 to +30

  19. SOHO ERNE higherbackground EPHIN: wide-angle vs parallel geometry EPHIN Valtonen et al (2001)

  20. SOHO A > 0 A < 0

  21. Helios 1974/76-1985 r: 0.29-0.98 CsE Kiel experiment 3.8-27 MeV/n

  22. Proton energy spectrum vs radial profile

  23. Ulysses 1990-2009 r: 1.4-5.4 CsE inclination 80 LET: 1.8-8.5 MeV PHA

  24. Ulysses radial variation -45+ 30 polar radial minimum is observed but in polar region

  25. Ulysses latitudinal variation Witcombe et al. (1995)

  26. Ulysses latitudinal variation 1994-97 + 2006-07 asymmetric pedestal centred at 10 south for both polarities Heliospheric current sheet: shifted southward(Mursula,Hiltula, 2003) streamer belt: shifted towards positive hemisphere(Zieger & Mursula, 1998)

  27. Ulysses energy spectrum Energy spectrum A < 0 fluxes lower polar spectrum flat

  28. Voyager 1-2 Voyager-1 May 2012: 121 AU (heliopause?)

  29. Voyager energy spectrum radial profile

  30. Radial profile 0,3-85 AU near-ecliptic fluxes: shallow minimum at 2-5 AU? 5-20 AU higher activity? polar fluxes: constant?

  31. Fe suprathermal quiet-time energy spectra ACE ULEIS low-FIP ions: 3 distinct groups Zeldovich et al (poster no 451) Fe charge state: 15-16 SEP remnants? poor statistics (ACE SEPICA, B. Klecker) SEP sw corona

  32. 3He, He+ nearly absent in solar wind 3He:extended emission periods (Mason, 2007) 3He rich events without obvious solar source – flare remnants or reconnection - quiet Sun? Gomez et al (2000)

  33. Heavy ions ACE, 1 AU (Reames, 1999) ions with anomalous component also in outer Heliosphere no anomalous component flat: SH + galactic

  34. Origin of low-flux ions at 1-30 MeV/n • micro-nano-picoflareSEP events (inner Heliosphere, polarregions) • SEP fluence distribution E-a(Miroshnichenko et al, 2001) • a 1,0 (<103 pfu) a 1,53 (>103 pfu) • solar flare energy distribution • dn/dE = AE-a, a 1,8 (51019 - 31024 J)Hudson (1991) • microflares: a 2,3-2,6 (1027 - 1019 J)Krucker & Benz (1998) • continuation to lower energies? • other active structures below flare threshold: X-ray bright points,disappearing ribbons, etc. • remnants ofearlier large SEP events, CIR post acceleration • (streamer belt) • anomalous, termination shock particles

  35. Future prospects • Large geometry factor, low-background telescopes  • heavier nuclei • <1 AU: Solar Orbiter (0.28 AU, 2017), • Solar Probe Plus (0.03 AU, 2018) • Solar Sentinels (6 s/c, 4 at 0.25 AU, 2017?) • suprathermal spectrum • energetic ions: better resolution of small SEPs • exploration of 1-20 AU region (near-ecliptic) • polar regions<1 AU • charge-state measurements at low solar activity

  36. Thank you for your attention!

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