energy spectra of suprathermal and energetic ions at low solar activity
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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Energy spectra of suprathermal and energetic ions at low solar activity
Károly Kecskeméty Wigner Research Centre for Physics, Budapest, Hungary
23rd European Cosmic Ray Symposium, Moscow, 5 July 2012
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Outline
energy spectra suprathermal 100 keV-1 MeV energetic 1-30 MeVvariability, quiet-time periodsprotons, radial variation: Helios, 1 AU, Ulysses, Voyagerlatitude variation: Ulysses3He, heavy nuclei 1-30 MeV/npopulations, acceleration mechanismsfuture prospects
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measurement: counting rates
m,Z,q (E,r,,,t) fZ,m,q (x, v, t)
differential flux phase space density
m,Z elemental/isotopic compositionq charge state composition
E energy spectrum r, heliocentric radial and latitudinal variation pitch angle distribution/anisotropy t short-term: transients, fluctuations
long-term: solar cycle, 22-year
Energetic charged particles
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Cosmic ray energy spectrum
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Ion populations in the Heliosphere
Gloeckler (2008)
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Fluence spectrum
Mewaldt et al. (2007)
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Variability
• solar wind proton flux density: 2x108 /cm2 s (high-speed) 4x108 /cm2 s (low-speed, Wang, 2010)
• suprathermals: ~100• 1-10 MeV >107
• 100 MeV ~103
• 1 GeV (galactic) factor of <2
~3 GeV
solar/interplanetary activity: fluctuating processhigh fluxes – localized source, low fluxes - global
(Feldman et al, 1978)
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Gloeckler & Fisk (2006)
Variability (100 keV-100 MeV)
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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)
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Definition: - ”no event” (depends on solar activity) - low particle flux (depends on energy) - low fluctuation levelbackground problem: pulse-height analysis needed difficult at <1 MeV, small geometry factor poor statistics at >1 MeV
IMP-8 protons (1-25 MeV)
Quiet time periods
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accelerated solar wind (suprathermal ions) SEP event remnants micro-/nano-/pico SEP events CIRs/GMIRs (backstreaming at <1 AU) interplanetary shocks turbulence magnetospheric – cometary ions ionized neutrals pick-up anomalous component, TSP
Particle sources at quiet times
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Suprathermal energies
ACE, Ulysses: universal spectrumf ~ v-5 J ~ E-1,5 up to ~150 keVparticular case of -distribution
solar wind plasma: in turbulent quasi-equilibrium Lorentzian -distributionsuperhalo: Lin (1998)Gloeckler (2003) up to 100 keV/npickup: comets, dust, outer sources
1 AUMason & Gloeckler (2011)
seed population for energeticparticles
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Very quiet periods
Mason & Gloeckler (2011)
1977
2007-09
spectral slope:steepening at >300 keV/n
protons-2.7 in 1977-2.1 in 2007-094He-2.6 in 1977-2.6 to 2.0 in 2007-09composition: CIR-like
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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 -distribution)
Drake et al (2010): magnetic reconnection – also E-1.5
Mason & Gloeckler (2011)
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Spectral minimum: 1-30 MeV (1 AU)
large fluctuationsbackground (instrumental, neutrals, high-energy?)small size detectors poor statistics<1 proton/day
Logachev et al (2002)
fluxes are lower atnegative magneticpolarity (qA < 0, 1986)
1996
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Protons at 1 AU
energy spectrum: good fit with sum of two populations
J(E) = AE- + CE-
solar/heliospheric galactic
spectral parametersobtained from best fitsto spectra
1.3 for protons(force-field = 1)
Kecskeméty et al (2011)
IMP-8
Gomez et al (2000)
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minimum: SH moves downwards, galactic upwards Emin is shifted to lower energies
Variation of spectral parameters with solar activity
IMP-8, Logachev et al. (2002)
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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
Radial and latitude variation
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SOHO
ERNE higher backgroundEPHIN: wide-anglevs parallel geometry
Valtonen et al (2001)
EPHIN
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A > 0 A < 0
SOHO
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Helios
1974/76-1985r: 0.29-0.98 CsEKiel experiment3.8-27 MeV/n
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Proton energy spectrum vs radial profile
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Ulysses
1990-2009r: 1.4-5.4 CsEinclination 80LET: 1.8-8.5 MeV PHA
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Ulysses radial variation
radial minimum is observedbut in polar region
-45 + 30
polar
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Ulysses latitudinal variation
Witcombe et al. (1995)
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asymmetric pedestal centred at 10 south for both polaritiesHeliospheric current sheet: shifted southward (Mursula, Hiltula, 2003)
streamer belt: shifted towards positive hemisphere (Zieger & Mursula, 1998)
Ulysses latitudinal variation
1994-97 +2006-07
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Energy spectrumUlysses energy spectrum
A < 0 fluxeslowerpolar spectrumflat
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Voyager 1-2
Voyager-1 May 2012: 121 AU (heliopause?)
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Voyager
energy spectrum radial profile
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Radial profile 0,3-85 AU
near-ecliptic fluxes:shallow minimumat 2-5 AU?5-20 AU higher activity?polar fluxes: constant?
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Fe suprathermal quiet-time energy spectra
Zeldovich et al (poster no 451)
ACE ULEISlow-FIP ions:3 distinct groups
Fe charge state: 15-16SEP remnants?poor statistics(ACE SEPICA, B. Klecker)
SEP
sw
corona
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3He, He+
nearly absent in solar wind3He: extended emission periods (Mason, 2007)3He rich events without obvious solar source – flare remnants or reconnection - quiet Sun?
Gomez et al (2000)
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Heavy ions
ions with anomalous componentalso in outer Heliosphere
no anomalous component flat: SH + galactic
ACE, 1 AU(Reames, 1999)
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Origin of low-flux ions at 1-30 MeV/n
• micro-nano-picoflare SEP events (inner Heliosphere, polar regions) SEP fluence distribution E- (Miroshnichenko et al, 2001)
1,0 (<103 pfu) 1,53 (>103 pfu) solar flare energy distribution dn/dE = AE-, 1,8 (51019 - 31024 J) Hudson (1991)
microflares: 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 of earlier large SEP events, CIR post acceleration (streamer belt)• anomalous, termination shock particles
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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 SEPsexploration of 1-20 AU region (near-ecliptic)polar regions <1 AU charge-state measurements at low solar activity
Future prospects
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