The PAMELA Experiment: a Cosmic-Ray Experiment Deep Inside the Heliosphere Mirko Boezio INFN Trieste, Italy On behalf of the PAMELA collaboration ICRC 2017, Busan July 18th 2017

Mirko Boezio, ICRC 2017, Busan, 2017/07/18

Mirko Boezio, ICRC 2017, Busan, 2017/07/18

PAMELA scientific goals Precise measurements of protons, electrons, their antiparticles and light nuclei in the cosmic radiation Search for Dark Matter indirect signatures Search for antihelium (primordial antimatter) and new form of matter in the Universe (Strangelets?) Investigation of the cosmic-ray origin and propagation mechanisms in the Galaxy, the heliosphere and the terrestrial magnetosphere detailed measurement of the high energy particle populations (galactic, solar, geomagnetically trapped and albedo) in the near-Earth radiation environment

PAMELA Instrument Italy: Russia: Germany: Sweden: Bari Florence Frascati Trieste Naples Rome CNR, Florence Moscow St. Petersburg Russia: Germany: Siegen Sweden: KTH, Stockholm

1998:December, signed MoU between INFN and Russian Space Agency 2006:June 15, Launch 2016: January, downlink operation were terminated PAMELA had been in nearly continuous data-taking mode for nearly a solar cycle

Mirko Boezio, ICRC 2017, Busan, 2017/07/18 Quasi polar and elliptical orbit Inclination ~ 70° Altitude ~ 300 - 600 km From 2010 circular orbit PAMELA Resurs-DK1 Mass: 6.7 tonnes Height: 7.4 m Solar array area: 36 m2 Mirko Boezio, ICRC 2017, Busan, 2017/07/18

PAMELA J. Cronin ,T.K. Gaisser & S.P. Swordy, Sci. Amer. 276 (1997) 44

PAMELA Results: Positron Fraction Secondary production Moskalenko & Strong 98

PAMELA Results: Positrons Results confirmed by Fermi and, especially, AMS-02! Solar modulation

PAMELA Results: Antiprotons Secondary production calculations

PAMELA antiproton results vs BESS Polar & AMS-02: Agreement!

PAMELA Results: Protons and Helium Nuclei O. Adriani et al. 2011, PAMELA Measurements of Cosmic-Ray Proton and Helium Spectra

Results confirmed by AMS-02: p PAMELA data  Jul 2006 ÷ Mar 2008 AMS02 data  May 2011 ÷ Nov 2013 O. Adriani et al., Phys. Rep. 544 (2014) 323 M. Aguilar et al., PRL 114 (2015) 171103  solar modulation Mirko Boezio, ICRC 2017, Busan, 2017/07/18

Results confirmed by AMS-02: He PAMELA data  Jul 2006 ÷ Mar 2008 AMS02 data  May 2011 ÷ Nov 2013  solar modulation O. Adriani et al., Science 332 (2011) 6025 M. Aguilar et al., PRL 115 (2015) 211101 Mirko Boezio, ICRC 2017, Busan, 2017/07/18

PAMELA Results: Electrons Solar modulation e-+e+ e- Solar modulation Solar modulation Solar modulation O. Adriani et al., ApJ 810 (2015) 142 O. Adriani et al., to appear in Nuovo Cimento (2017)

Heliosphere Contribution PAMELA

Solar Cycle PAMELA SOLAR CYCLE nasa.gov: solarcycle-primer.html NOAA/Space Weather Prediction Center PAMELA SOLAR CYCLE Solar activity rises and falls over an 11 year cycle Can be shorter/longer Different events during the cycle Activity correlates with Sunspot Number PAMELA observations covers ~ one solar cycle

Heliospheric conditions during PAMELA observations Neutron Monitor counts data from http://cosmicrays.oulu.fi/ PAMELA observations covers ~ one solar cycle Mirko Boezio, ICRC 2017, Busan, 2017/07/18

Time Dependance - Electron Flux Evolution of the electron (e-) energy spectrum from July 2006 to December 2009 R. Munini SH132 M. Potgieter SH008 The ratios between the measured e- fluxes from January 2007 till December 2009 and the measured fluxes for the period July-November 2006 with the corresponding computed spectra. O. Adriani et al., ApJ 810 (2015) 2, 142; M. S. Potgieter et al., ApJ 810 (2015) 2, 141

Time dependance of the e-, e+ and p flux over the last solar minimum The PAMELA positron spectra over the last solar minimum Preliminary Variation of the e-, e+ and p flux between July 2006 and December 2009 R. Munini SH132 M. Potgieter SH008

Heliospheric conditions during PAMELA observations Neutron Monitor counts data from http://cosmicrays.oulu.fi/ PAMELA observations covers ~ one solar cycle Mirko Boezio, ICRC 2017, Busan, 2017/07/18

Time dependence of the proton flux July 2006-December 2014 Preliminary

Time dependence of the proton flux July 2006-December 2014 Preliminary! SEP removed Temporal period: 1 year M. Martucci & B. Panico, CRD087 Mirko Boezio, ICRC 2017, Busan, 2017/07/18

Mirko Boezio, ICRC 2017, Busan, 2017/07/18 PAMELA vs AMS-02: p PAMELA data  Jul 2006 ÷ Mar 2008 AMS02 data  May 2011 ÷ Nov 2013  solar modulation Mirko Boezio, ICRC 2017, Busan, 2017/07/18

PAMELA vs AMS-02: p 2011-2013 O. Adriani et al., to appear in Nuovo Cimento (2017)

Time dependence of Helium nuclei flux July 2006-December 2014 Preliminary! SEP removed Temporal period: 1 year M. Martucci & B. Panico, CRD087 Mirko Boezio, ICRC 2017, Busan, 2017/07/18

Positron-electron ratio time dependence R. Munini, SH 132 Mirko Boezio, ICRC 2017, Busan, 2017/07/18

Positron-electron ratio time dependence R. Munini, SH 132 Mirko Boezio, ICRC 2017, Busan, 2017/07/18

Time dependance of the positron fraction R. Munini, SH 132 See also J.-L. Raath, SH019 Mirko Boezio, ICRC 2017, Busan, 2017/07/18

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 field lines 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

List of PAMELA events (2006-2014) Event No. Date Class Location 1 2006 Dec 13 X3.4/4B S06W23 2 2006 Dec 14 X1.5/-- S06W46 3 2011 Mar 21 M3.7/-- >W90 4 2011 Jun 07 M2.5/2N S21W54 5 2011 Sep 06 M5.3/-- N14W07 6 2011 Sep 07 X2.1/-- N14W18 7 2011 Nov 04 ? 8 2012 Jan 23 M8.7/-- N28W21 9 2012 Jan 27 X1.7/1F N27W71 10 2012 Mar 07 X5.4/- N17E27 11 2012 Mar 13 M7.9/-- N17W66 12 2012 May 17 M5.1/1F N11W76 13 2012 Jul 07 X1.1/-- S13W59 14 2012 Jul 08 M6.9/1N S17W74 Event No. Date Class Location 15 2012 Jul 19 M7.7/-- S13W88 16 2012 Jul 23 ? >W90 17 2013 Apr 11 M6.5/3B N09E12 18 2013 May 22 M5.0/-- N13W75 19 2013 Sep 30 C1.3/-- N17W29 20 2013 Oct 28 M5.1 N08W71 21 2013 Nov 02 22 2014 Jan 06 23 2014 Jan 07 X1.2/-- S15W11 24 2014 Feb 25 X4.9/B S12E82 25 2014 Apr 18 M7.3/-- S20W34 26 2014 Sep 01 27 2014 Sep 10 X1.6/-- N14E02 All flares are associated with (halo) CMEs. Red=back-side events; blue=eastern limb events Flare data from https://cdaw.gsfc.nasa.gov/CME_list/sepe/ 7

SEP Energy Spectra 2006 December 13 Data were fit to both a single power law and an Ellison-Ramaty spectrum (1986), Φ(E)=N0 E –γ e–E/Ec M. Mergè, SH165 J. Ryan, APS 2017 In each case where statistics allow, pure power-law spectra are consistently rejected. SEP spectra, over the current PAMELA mission database, exhibit a terminus to the spectrum, probably indicative of the limits of the acceleration process. Cutoff energies fall above and below the GLE threshold (~1 GV). Three GLEs are among the group, but also some events falling above 1 GV that were not registered as GLEs, but might have. From the spectrum perspective, we see no qualitative distinction between those events that are GLEs, those that could be, or those that are not. preliminary! 6

Multiparticle observation of Forbush decrease 2006 December – 2007 January Preliminary The proton and the helium amplitude and recovery time are in good agreement while electrons on average shows a faster recovery. This could be interpreted as a charge-sign dependence due to the different global drift pattern between proton and electrons. R. Munini, SH153

Short and mid-term time variations in the proton flux A periodicity of about 410 days is observed in the proton flux which could be due to known variation in solar activity, called Quasi-Biennial Oscillations, but is also consistent with Jupiter periodicity. M. Ricci, CRD080 Preliminary 2006 December – 2007 January A 13:5 days periodicity is found in the proton flux between December 2006 and March 2007. This phenomenon could be interpreted as an effect of prominent structures of compressed plasma in the solar wind (CIRs) or to the latitudinal gradient due to the crossing of the HCS. R. Munini, SH153

Measured cutoff latitudes Time profile of the geomagnetic cutoff latitudes measured by PAMELA for different rigidity bins during December 13 2006 GLE event Data missing from 10:00 UT on Dec 13 until 09:14 UT on Dec 14 because of an onboard system reset of the satellite initial phase recovery phase main phase O. Adriani et al., Space Weather 14 (2016) 210, featured as a Research Spotlight on https://Eos.org

PAMELA overall results Review papers: O. Adriani et al., Phys. Rept. 544 (2014) 323 O. Adriani et al., to appear in Nuovo Cimento (2017)

Thanks!

Mirko Boezio, ICRC 2017, Busan, 2017/07/18 Spare Slides Mirko Boezio, ICRC 2017, Busan, 2017/07/18

PAMELA detectors Main requirements  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 3He tubes + polyethylene moderator: High-energy e/h discrimination Overview of the apparatus GF: 21.5 cm2 sr Mass: 470 kg Size: 130x70x70 cm3 Power Budget: 360W Spectrometer microstrip silicon tracking system + permanent magnet It provides: - Magnetic rigidity  R = pc/Ze Charge sign Charge value from dE/dx

Boron and carbon fluxes and B/C Tracking performance: σx = 14 μm, σy = 19 μm MDR = 250 GV Modelization of cosmic-ray propagation in the Galaxy O. Adriani et al., ApJ 791 (2014), 93

Lithium and Beryllium Isotopes β (ToF) vs. Rigidity or Multiple dE/dx (Calorimeter) vs. rigidity Lithium Beryllium Ratio 7Li / 6Li 7Be / (9Be + 10Be) W. Menn, CRD040