1. 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

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

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

4. 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

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

6. 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

7. Mirko Boezio, ICRC 2017, Busan, 2017/07/18
Quasi polar and elliptical orbit
Inclination ~ 70°
Altitude ~ 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

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

9. PAMELA Results: Positron Fraction
Secondary production Moskalenko & Strong 98

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

11. PAMELA Results: Antiprotons
Secondary production calculations

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

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

14. 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)
 solar modulation
Mirko Boezio, ICRC 2017, Busan, 2017/07/18

15. 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)
Mirko Boezio, ICRC 2017, Busan, 2017/07/18

16. 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)

17. Heliosphere Contribution
PAMELA

18. 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

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

20. 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

21. 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

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

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

24. 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

25. 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

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

27. 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

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

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

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

31. 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

32. 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 7

33. 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

34. 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

35. 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

36. Measured cutoff latitudes
Time profile of the geomagnetic cutoff latitudes measured by PAMELA for different rigidity bins during December 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

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

38. Thanks!

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

40. 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

41. 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

42. 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