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!