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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
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
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
Cosmic ray energy spectrum
Ion populations in the Heliosphere
Gloeckler (2008)
Fluence spectrum
Mewaldt et al. (2007)
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)
Gloeckler & Fisk (2006)
Variability (100 keV-100 MeV)
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)
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
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
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
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
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)
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
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)
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)
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
SOHO
ERNE higher backgroundEPHIN: wide-anglevs parallel geometry
Valtonen et al (2001)
EPHIN
A > 0 A < 0
SOHO
Helios
1974/76-1985r: 0.29-0.98 CsEKiel experiment3.8-27 MeV/n
Proton energy spectrum vs radial profile
Ulysses
1990-2009r: 1.4-5.4 CsEinclination 80LET: 1.8-8.5 MeV PHA
Ulysses radial variation
radial minimum is observedbut in polar region
-45 + 30
polar
Ulysses latitudinal variation
Witcombe et al. (1995)
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
Energy spectrumUlysses energy spectrum
A < 0 fluxeslowerpolar spectrumflat
Voyager 1-2
Voyager-1 May 2012: 121 AU (heliopause?)
Voyager
energy spectrum radial profile
Radial profile 0,3-85 AU
near-ecliptic fluxes:shallow minimumat 2-5 AU?5-20 AU higher activity?polar fluxes: constant?
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
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)
Heavy ions
ions with anomalous componentalso in outer Heliosphere
no anomalous component flat: SH + galactic
ACE, 1 AU(Reames, 1999)
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
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
Thank you for your attention!