Solar Physics with the PAMELA and CSES/Limadou Missions
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Solar physics with the PAMELA and CSES/Limadou missions ROBERTA SPARVOLI UNIVERSITY OF ROMA “TOR VERGATA” AND INFN PAMELA Payload for Matter/antimatter Exploration and Light-nuclei Astrophysics • Direct detection of CRs in space • Main focus on antiparticles (antiprotons and positrons) • PAMELA on board of Russian satellite Resurs DK1 • Orbital parameters: - inclination ~70o (low energy) - altitude ~ 360-600 km (elliptical) – now 500 km (circular) Launch from Baykonur à Launched on 15th June 2006 à PAMELA in continuous data-taking mode since then! à Soon celebrates 10 years! Main requirements à high-sensitivity antiparticle identification and precise momentum measure + - Time-Of-Flight plastic scintillators + PMT: - Trigger - Albedo rejection; - Mass identification up to 1 GeV; - Charge identification from dE/dX. Electromagnetic calorimeter W/Si sampling (16.3 X0, 0.6 λI) - Discrimination e+ / p, anti-p / e- (shower topology) - Direct E measurement for e- Neutron detector plastic scintillators + PMT: 2 GF: 21.5 cm sr - High-energy e/h discrimination Mass: 470 kg Size: 130x70x70 cm3 Spectrometer Power Budget: 360W microstrip silicon tracking system + permanent magnet It provides: - Magnetic rigidity à R = pc/Ze MDR up to 1.2 TV - Charge sign - Charge value from dE/dx e- Propagation of cosmic rays Diffusive shock acceleration Propagation through Galaxy Propagation through the Heliosphere �~�$% � ~�$%$' � variation < 30GeV PAMELA published results Antiproton flux + antiproton/proton ratio (100 MeV-300 GeV) Positron flux + positron/electron ratio (100 MeV-300 GeV) Electron flux (1 – 500 GeV) Proton and helium flux (1 GeV – 1.2 TeV) B/C ratio (500 MeV – 100 GeV) H and He isotope flux AntiHe/He ratio Proton/electron/positron ratio flux vs. time – solar modulation Trapped proton and antiproton flux, albedo protons SEP data (13 December 2006 and 17 May 2012 event) Anisotropy of positrons and electrons Adriani et al. - Science - 332 (2011) 6025 H & He absolute fluxes • First high-statistics and high-precision measurement over three decades in energy • Deviation from single power law @98% CL • Spectral hardening ~0.2÷0.3 @R~235GV PAMELA dataà Jul 2006 ÷ Mar 2008 Adriani et al. - Science - 332 (2011) 6025 H & He absolute fluxes • First high-statistics and high-precision measurement over three decades in energy • Deviation• Spectral featuresfrom single@injection ? power• Different law @98%astrophysical CL objects? • Spectral• Propagation hardeningfeature not ~0.2constrained÷0.3 by S/N ratio @R~235GVdata? PAMELA dataà Jul 2006 ÷ Mar 2008 Adriani et al. - Science - 332 (2011) 6025 H & He absolute fluxes • First evidence of different H and He slopes above 10 GV αHe-αp = 0.078 ±0.008 • Spectral features @injection? • Different astrophysical objects? • Propagation feature not constrained by S/N ratio data? B/C ratio B nuclei are of pure secondary origin Adriani C,N,O + ISM B + … et al. al. et B/C provides the - strongest constraint to ApJ propagation parameters - so far 791 93(2014) PAMELA data consistent with previous GALPROP code tuned to PAMELA B&C data measurements and with • Plain diffusion model (Vladimirov et al. 2012) a standard scenario • Solar modulation: spherical model ( φ=400MV ) Adriani et al. -- Nature 458 (2009) 607; Positrons -- Astropart. Phys. 34 (2010) 1 – PRL – 111 (2013) 081102 – PR 544 (2014) 323 First measurement ö extending up to 200 GV positron excess ö • Clear evidence for an hardening of positron ösolar modulationö spectra (charge-dependent) Adriani et al. -- Nature 458 (2009) 607; Positrons -- Astropart. Phys. 34 (2010) 1 – PRL – 111 (2013) 081102 – PR 544 (2014) 323 First measurement ö extending up to 200 GV positron excess ö • Clear evidence for an hardening of positron ösolar modulationö spectra (charge-dependent) Dark matter annihilation/decay • Lepton vs hadron yield must be consistent with p-bar observation Astrophysical processes • Pulsars, «tick» sources • Large uncertainties on environmental parameters • Must be consistent with otherCR components PAMELA Results 7 -1 10 106 s sr GeV/N) 2 105 Proton (SAA) All 10Flux (m 4 Proton (Flare) Proton particles 103 Helium 2 10 2 PAMELA H (rat.) 3He (rat.) 10 Antiproton (SAA) results Carbon Electron 1 Boron 10-1 Positron Results span 4 10-2 decades in Antiproton energy and 13 in 10-3 fluxes 10-4 10-5 10-6 10-7 10-1 1 10 102 103 E (GeV/N) CRs in the heliosphere LONG- TERM CR- FLUX VARIATION SOLAR- PARTICLE EVENTS ( SEPS) Solar cycles & CR modulation 22-year cycle 11-year cycle Cycle 20 Cycle 21 Cycle 22 Cycle 23 The solar wind • Convection with solar-wind velocity V • Adiabatic energy changes (∝ � * � ) Heliospheric magnetic field (HMF) A>0 magnetic-field reversal A<0 22-year cycle to return to the same polarity Drift & diffusion A>0 A<0 A<0 HP HP HP Strauss et (2012)al. HCS HCS HCS • Diffusion, driven by small-scale HMF irregularities • Drift caused by gradients and curvature in the global HMF Drift path GCR qA > 0 qA < 0 GCR • Drift path changes at each field reversal à 22-year cycle • Asimmetry between particle of opposite charge àcharge dependent solar modulation PAMELA observations during 23° solar cycle expected recovery A<0 PAMELA Cycle 23 Neutron Monitor counts Maximum inclination of HCS (N-S mean) Data from http://cosmicrays.oulu.fi/ Computed HCS tilt angle Data from http://wso.stanford.edu/ Long-term variation of GCR protons during (Potgieteret al. 2014) 23° solar • 3D model • Parker eq: convection, minimum drift, diffusion& adiabatic en.changes Evolution of the proton energy spectra §from July 2006 to December 2009 à Minimum solar activity Adriani et al. -- ApJ - 765 (2013) 91 Potgieter et al. – Solar Phys. – 289 (2014) 391 Potgieteret al. – ApJ – 810 (2015) 141 Long-term Adriani et al. -- ApJ -- 810(2015) 142 variation of GCR electrons during 23° solar minimum Evolution of the electron energy spectra §from July 2006 to December 2009 § à Minimum solar activity • 3D model • Parker eq: convection, drift, diffusion& adiabatic en.changes Measured down to 80 MeV Particle- dependent solar modulation • Larger modulation effect for protons than electrons • Proton modulation consistent with that of positrons (preliminary) PAMELA observations during 24° solar cycle A<0 A>0 PAMELA Cycle 23 Cycle 24 Neutron Monitor counts Maximum inclination of HCS (N-S mean) Data from http://cosmicrays.oulu.fi/ Computed HCS tilt angle Data from http://wso.stanford.edu/ Long-term variation of GCR protons towards 24° solar maximum Evolution of the proton energy spectra from 2006 to present à Modeling during solar maximum activity (not-stationary condition) O. Adriani et al., PRL, accepted 10 May 2016 – Highlighted !! Evolution of the electron charge ratio: sign- dependent solar modulation à -> Analysis from July 2006 to December 2015, covering the period from the minimum of solar cycle 23 (2006-2009) till the middle of the maximum of solar cycle 24. Results provide the first clear and continuous observation à à polarity reversal of the heliospheric magnetic of how drift effects on solar modulation have unfolded field took place between with time from solar minimum to solar maximum and 2013 and 2014. their dependence on the particle rigidity and the cyclic polarity of the solar magnetic field. Solar energetic particles (SEPs) Sun can accelerate particles up to relativistic energies • Magnetic reconnections • CME-driven shock SEPs can be observed in the interplanetary space Often associated to other solar phenomena, eg: • X and gamma-ray flares • Coronal-mass ejections (CMEs) • ... Magnetic fieldlines SEP observation on Earth: • Propagation of SEPs along IMF lines Earth must be magnetically connected • Anisotropic emission flux observed on Earth depends on geomagnetic location The acceleration of solar particles • The site/mechanisms of acceleration could be studied by analyzing the differential spectra of protons à fit with specific functions that describe different mechanisms • Try to disentangle from transport mechanisms • Events «well connected» (in which the Parker spiral connects directly the Sun with the Earth) are perfect because the transport effects are less important The event of June 7 2011 Preliminary The event of March 7 2012 Preliminary The event of April 11 2013 Preliminary Multi-particle measurements Helium and protons flux evolution vs. time and helium enhancement studies are possible for events that present traces of He Dec 13°-14° 2006 Adriani et al. - ApJ - 742 (2011) 102 SEP event First instrument to directly measure relativistic SEPs in near-Earth space. GLE It bridges the gap between low-energy direct space- based observations (GOES) with high-energy indirect gound-based measurements (NM GLEs) PAMELA observationdone during passages over high-latitude regions May 17°, 2012 SEP event Asymptotic direction during first polar pass after the event onset • First observed GLE of 24° solar cycle • Earth magnetically connected to the Sun • Associated to M1.5-class X-ray flare • Extended emission (>100MeV) seen by Fermi-LAT Unique possibility to measure pitch angle distribution over broad IMF direction energy range, to disentangle interplanetary Pitch angle transport process Adriani et al. - ApJL - 801 (2015) L3 Adriani et al. - ApJL - 801 (2015) L3 May 17°, 2012 SEP event First evidence of two simultaneous particle populations: § High rigidity component consistent with NM where particles are field aligned à Beam width ~40-60o (not scattered) § Low rigidity component shows significant scattering for pitch angles ~90o § The time coincidence of the two