sign in sign up
<<
Home , Coronal mass ejection

PoS(ICRC2017)1091 , , 6 , , 8 , 15 5 18 , , 3 15 , , http://pos.sissa.it/ 16 13 , , A. Bruno 11 3 , B. Panico , M. Simon 5 1 13 , S. V. Koldashov ,V. Malakhov , E. Vannuccini 15 , G. A. Bazilevskaya 15 5 19 , , , S. Bottai 4 , M. Mergé 1 1 , G. Castellini 18 , N. Zampa 12 , G. Osteria , 1 3 11 , S. B. Ricciarini , A. Leonov 6 17 , A. Vacchi , A. V. Karelin , W. Menn 6 , N. Mori 15 15 8 , , V. Bonvicini 7 , G. Zampa 3 , 2 15 , G. C. Barbarino 3 , , M. Casolino 2 10 , M. Ricci 16 , 11 , M. Bongi , A. Monaco , A. N. Kvashnin , A. M. Galper , Y. I. Stozhkov 9 1 9 3 , 14 , A. G. Mayorov , Y. T. Yurkin , 2 11 17 , O. Adriani 15 , 1 , P. Carlson 16 5 , P. Picozza 10 ,E. Mocchiutti , S. Y. Krutkov , P. Spillantini , R. Munini 15 , V. Di Felice 15 1 ∗ 16 , 11 , S. A. Voronov , M. Martucci , E. A. Bogomolov , D. Campana 9 8 11 , 8 11 7 , M. Pearce 3 [email protected] Copyright owned by the author(s) under the terms of the Creative Commons INFN, Sezione di Trieste I-34149 Trieste,University Italy of Florence, Department of Physics,INFN, I-50019 Sezione Sesto di Fiorentino, Florence, Florence, I-50019 Italy SestoUniversity Fiorentino, of Florence, Naples Italy “Federico II”, DepartmentINFN, of Sezione Physics, di I-80126 Naples, Naples, I-80126 Italy Naples,Lebedev Italy Physical Institute, RU-119991, Moscow, Russia University of Bari, Department of Physics,INFN, I-70126 Sezione Bari, di Italy Bari, I-70126 Bari,Ioffe Italy Physical Technical Institute, RU-194021 St.KTH, Petersburg, Russia Department of Physics, and the Oskar Klein Centre for CosmoparticleINFN, Physics, Sezione AlbaNova di Rome “Tor Vergata”, I-00133RIKEN, Rome, Advanced Italy Science Institute, Wako-shi, Saitama,IFAC, Japan I-50019 Sesto Fiorentino, Florence, Italy Agenzia Spaziale Italiana (ASI) Science DataNational Center, Research I-00044 Nuclear Frascati, University Italy MEPhI, RU-115409University Moscow of Rome “Tor Vergata”, Department ofINFN, Physics, Laboratori I-00133 Nazionali Rome, di Italy Frascati, ViaUniversität Enrico Siegen, Fermi Department 40, of I-00044 Physics, Frascati, Italy D-57068University Siegen, of Germany Udine, Department of Mathematics and Informatics, I-33100 Udine, Italy c R. Sparvoli G. Vasilyev University Centre, SE-10691 Stockholm, Sweden E-mail: V. V. Mikhailov L. Marcelli P. Papini Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). C. De Santis S. Koldobskiy R. Bellotti F. Cafagna Mirko Boezio The PAMELA Experiment: A Cosmic Ray Experiment Deep Inside the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 PoS(ICRC2017)1091 Speaker. It was the 15th of June ofthe 2006 Baikonur when the cosmodrome PAMELA in -borne Kazakstan. experiment was Then,high-precision launched for from measurements nearly of ten the years, charged PAMELA hasera component been of of making precision the studies cosmic inproduction, opening cosmic acceleration and a rays propagation new of and cosmic challenging raysstudy in our of the basic the galaxy time and vision dependence in of of the the heliosphere. the23rd various The components mechanisms solar of of minimum the cosmic through radiation fromeffects the the as unusual maximum well as of charge solar signsolar cycle dependence. energetic 24 PAMELA particle measurement clearly events of fills shows themeasured the energy solar in existing spectra modulation energy space during gap and between thedifferent the ground-based regions highest domain. of energy Finally, particles the by , samplingmagnetosphere. PAMELA the In data particle this provide radiation highlight a in paper,solar detailed PAMELA and main study heliospheric results of physics as with the well PAMELA will as be s recent presented. progress about ∗ 35th International Cosmic Ray Conference 10-20 July, 2017 Bexco, Busan, Korea PoS(ICRC2017)1091 Mirko Boezio of 2006 from the He/He sensitivity th ) and with a period of about 94 ◦ 2 and comprises the following subdetectors (from top to 1 ), of new forms of matter, e.g. , was studied as well as possible structures in 7 − The PAMELA detector is built around a permanent magnet that hosts the tracking system In the following, PAMELA main results as well as recent progress about solar and heliospheric The apparatus is shown in Figure The PAMELA (a Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics) Initially planned for three years, PAMELA operation lasted until January 2016 when the data The PAMELA experiment is the results of the collaboration between Italian (Universities and The PAMELA main scientific objectives were the measurement of the energy spectra and 100 GeV/n. Furthermore, new physics such as existence of antinuclei (with a composed of six planes of double-sided silicon sensors, which form the magnetic spectrometer. bottom): a Time-of-Flight system (TOF),electromagnetic a imaging magnetic calorimeter, spectrometer, a an shower anticoincidence tail catcher system, scintillator an (S4) and a neutron detector. physics obtained with PAMELA data will be presented. 2. The PAMELA instrument of 10 cosmic ray (CR) spectra arising fromPAMELA was e.g. well dark suited matter to orthe new conduct astrophysical Galaxy, studies sources. solar of modulation Furthermore, CR effects, accelerationheliosphere the and and emissions investigate propagation of the mechanisms Solar particles in in Energetic the Particles Earth’s (SEPs) magnetosphere. inside the satellite experiment was designed toing study on the antiparticles. charged PAMELA component was of launched the with cosmic a Soyuz-U radiation, rocket focus- on June 15 transmission from the satellite to the ground stationproblems in with Moscow the was satellite. interrupted because The of operation technical withofficially the terminated satellite sometime and, in consequently, with 2016. PAMELA were January The 2016. last PAMELA data were transmitted to ground on 24 Istituto Nazionale di Fisica Nucleare(Lebedev I.N.F.N. Physical Structures), Institute, German Ioffe (Universitätversity Physical Siegen), MEPhI) Russian Technical Institute, and Swedish Nationalresearchers Nuclear (KTH from other Research Royal institutes Uni- Institute in Germany(North-West of University, (Christian-Albrechts-Universität, Potchefstroom) Kiel), and Technology) USA South institutes. (NASA Africa Goddard Space Flightico Center, Over State New University, Mex- the University of years, New Hampshire)science joined topics the ranging PAMELA Collaboration from on solar specific physics to studies of solar modulation effects. composition of the charged cosmic radiationSpecifically, from the few data tens allowed of the MeV studyspectrum up of up to the 1 to antiproton TeV 200 spectrum in GeV, kinetic upclei of energy. to spectra the 350 up GeV, of to spectrum the 1.2∼ up positron and to 0.6 600 TeV/n GeV, of respectively and the of and the helium nuclei nu- spectra (from Li to O) up to The PAMELA Experiment: A Cosmic Ray Experiment Deep Inside the Heliosphere 1. Introduction Baikonur cosmodrome (Kazakhstan). Thelite, apparatus a is commercial hosted Earth-observation on spacecraft. thebetween Russian 355 At Resurs-DK1 and first 584 satel- the km)minutes. orbit and In semipolar was 2010 (inclination elliptical the of (altitude orbit about varying was 70 set to be circular with an almost fixed altitude of about 550 km. PoS(ICRC2017)1091 ] and 4 Mirko Boezio ], here we will revise the 3 and the ionization energy , 6 interaction lengths) and is 1 2 . ]. 1 3 3 radiation lengths (0 . PAMELA and its sub-detectors. Figure 1: . The shower tail catcher and the neutron detector beneath provide 4 − shows the original PAMELA results on the galactic cosmic ray (GCR) positron frac- 2 p and Ze are respectively the particle momentum and charge, and c the speed of light. More details about the apparatus can be found in [ Reviews of most PAMELA results have already been published [ Figure The sampling imaging calorimeter has 16 1 references within). the main sub-detector used for hadron-lepton separation.of The the topological and shower energetic development information inpositron the of calorimeter the allows to order reach ofadditional a information 10 rejection for the power discrimination. of An protonevents anticoincidence in against system the is off-line used phase. to reject spurious 3. Review of PAMELA main scientific results most significant ones with a focus on their relevance for studies oftion solar along and with heliospheric other physics. previous measurements and a theoretical secondary prediction (see [ The magnetic spectrometer measureslosses the (dE/dx). The particle rigidity measurement rigidity is ron done through the = the impact reconstruction pc/Ze of points the on trajectoryto based the the tracking Lorentz planes force. andscintillator the The paddles resulting with Time-of-Flight determination the (ToF) first of systemspectrometer. two the comprises placed The curvature three above ToF due double and system layers the providestime third of the of immediately plastic measurements passage below of information the the with magnetic the particle the information velocity track on combining the length particle the derived incoming fromcharged direction the particles and are magnetic the distinguished curvature spectrometer. from in From positively the charged spectrometer particles. negatively The PAMELA Experiment: A Cosmic Ray Experiment Deep Inside the Heliosphere PoS(ICRC2017)1091 Mirko Boezio ] below about 14 ], along with other previous 4 ] and references within). 4 ] and, especially, by the AMS-02 magnetic 5 4 . ]. Solar modulation has large effects on low energy CRs 3 9 ]), here the differences at low energies will be addressed and explained 8 shows the all-electron ( plus positrons) spectrum measured by 4 ] as can be seen in Figure 6 Galactic cosmic ray positron fraction measured by PAMELA [ Undoubtedly the best known PAMELA result, these positron fraction data were extremely The significance of the high energy positron fraction PAMELA data have been extensively Traversing the heliosphere, GCR are scattered by the irregularities of the turbulent heliospheric PAMELA along with other recent measurements. The difference with AMS-02 [ intriguing because of the differencesteractions with of expectations for CR positrons nuclei produced withat by the low the interstellar inelastic energies medium in- respect at tosults high the were energies majority but proven also of correct for the by the older the differences measurements. Fermi telescope In [ subsequent years, the re- discussed elsewhere (e.g. [ as result of sign-charge dependence of the solar modulation. magnetic field (HMF) embedded intoeration the in solar the expanding and solar undergo wind.respect convection As to and a the adiabatic consequence, local decel- the interstellar intensity spectrum of [ CR at Earth decreases with spectrometer [ (less than a few GeV),negligible while above a the few effects tens of significantly GeV. Moreover, decreasesity because of of as CRs the the 11-year inside solar energies the activity heliosphere increase cycle, changesof the becoming with cosmic inten- time. rays. This can Figure be clearly seen in the energy spectra Figure 2: measurements and a theoretical secondary prediction (see [ The PAMELA Experiment: A Cosmic Ray Experiment Deep Inside the Heliosphere PoS(ICRC2017)1091 , ] ] 5 11 15 , 10 Mirko Boezio 1000 3 10 × 2 Energy [GeV] 3 10 300 Kinetic Energy [GeV] ], along with the recent Fermi [ 7 200 ] along with other recent results [ 2 3 10 100 × 2 2 10 40 5 30 40 30 20 BETS (1997+1998+2004) BETS (1997+1998+2004) ATIC (2001+2003)ATIC (2001+2003) H.E.S.S.(2004-2007)H.E.S.S.(2004-2007) Fermi-LAT(2008-2009)Fermi-LAT(2008-2009) AMS-02 PRL (2014)AMS-02 PRL (2014) PAMELA (new analysis) PAMELA (new analysis) 20 10 10 9 PAMELAPAMELA AMS-02AMS-02 FermiFermi 8 8 . Also in this case the differences at low rigidities can be ascribed 7 7 5 6 6 5 5 4 4 3 3 2 ], see Figure 2 1 17 , -1 ] measurements. Only statistical errors are shown. 16 1 10 6 2 × 5 10

0.1 10

0.3

0.2

All electron energy spectrum measured by PAMELA [ 0.15 0.05 0.25 0.35

Galactic cosmic ray positron fraction measured by PAMELA [ e ) e + (e /

s sr GeV) sr s [(m Flux ] ] GeV E ]. Only statistical errors are shown.

× × +

- + 2 -1 3 3 14 , A similar behavior, excellent agreement at high rigidities (above tens of GV) and differences at 13 , and AMS-02 [ lower rigidities, is found also in the proton and helium nuclei spectra measured by PAMELA [ 12 Figure 4: and AMS-02 [ 10 GeV respect to theconsidering excellent agreement that at PAMELA higher data energies referand can to AMS-02 be to a ascribed a period to period of solar of significantly modulation solar higher minimum solar (July activity (May 2006-December 2011-November 2009) 2013). Figure 3: The PAMELA Experiment: A Cosmic Ray Experiment Deep Inside the Heliosphere PoS(ICRC2017)1091 ]. 16 2000 2000 Mirko Boezio ] and AMS-02 15 ] and AMS-02 [ 1000 1000 15 Rigidity [GV] Rigidity [GV] Rigidity [GV] Rigidity [GeV] results from a linear fit between results from a linear fit between 0 0 300 300 PAMELAPAMELA AMS-02AMS-02 0.01 0.01 ± ± 200 200 = 1.01 = 0.98 0 0 P P 100 100 6 50 50 PAMELAPAMELA AMS-02AMS-02 40 40 30 30 p He 20 20 10 10 9 9 8 8 7 7 6 6 a 5 5 (b) 4 4 (a) (a) Top panel: comparison of the proton fluxes measured by PAMELA [ 1 1 1.1 1.1 0.8 0.8 0.9 1.2 0.9

1000 2500 2000 1500 3000 8000

12000 10000 14000

AMS / PAM / AMS AMS / PAM / AMS

Flux Flux s sr GV) sr s [(m R ] GV s sr GV) sr s [(m R Flux ] GV

× × × ×

-1 2 -1 2 2.7 2.7 2.7 2.7 ]. Lower panel: AMS-02 and PAMELA He flux ratio. The value of P 17 50 GV and 1 TV. Lower panel: AMS-02 and50 PAMELA GV proton and flux 1 ratio. TV. (b)[ Top The panel: value comparison of of P the helium fluxes measured by PAMELA [ Figure 5: The PAMELA Experiment: A Cosmic Ray Experiment Deep Inside the Heliosphere PoS(ICRC2017)1091 Mirko Boezio 1 GeV) particles < . The solar cycle can be 2 ]. In addition, long-term changes in the solar 18 7 that shows PAMELA trigger rate and neutron monitor counts 6 PAMELA trigger rate and Oulu neutron monitor count rate (data taken from Precise measurements of the time-dependent CR spectra are essential to understand the cosmic Cosmic rays colliding with molecules in the produce air showers of secondary particles including Another conclusion that can be drawn from these comparisons is the striking agreement be- As previously discussed, because of the interaction with the the CR intensity mea- 2 ray propagation through the heliosphere.tion Furthermore, of the this experimental system and provides theoretical informationThe investiga- that possibility can of be performing easily in-situ measurements appliedvironment makes to to the larger test interplanetary astrophysical the medium systems. theory the of ideal propagation en- of charged particles in magnetic fields underneutrons. conditions The neutron monitor count rate is thus proportional to the intensities of the CR flux at Earth. activity, i.e. the 11-year solarbehavior cycle, is produce illustrated time in variations in Figure the near-Earth CR intensity.clearly This noticed in both setsminimum) of followed data: by a increasing sharpdifferent counting decrease relative rate with increase from a over mid the leveling 2006only out solar in till in minimum PAMELA late trigger as mid 2009 rate well 2013 are (solar as (solarof due PAMELA the maximum). to instrument spikes the respect The (SEPs) higher to neutron sensitivity noticeable to monitors. nearly low energies ( (both normalized to mid 2006) measured by the Oulu neutron monitor tween various measurements, especially those of PAMELAquality and and AMS-02, which reliability is of testament these of results the and of the conclusion that can be drawn4. from them. Propagation in the heliosphere sured at Earth decreasesmeasured with just respect outside to the the heliospheric boundary local [ interstellar spectrum, i.e. the CR intensity as to different period of solar activity:for July AMS-02. 2006-Mar 2008 for PAMELA, May 2011-November 2013 Figure 6: http://cosmicrays.oulu.fi/) Data are normalized to July 2006. The PAMELA Experiment: A Cosmic Ray Experiment Deep Inside the Heliosphere PoS(ICRC2017)1091 ]. More 19 Mirko Boezio 2014 ]). It was expected 18 Time [Year] 2013 2012 24th 2011 shows this new proton spectrum compared 8 8 27 days time period. Holes are due to missing data from 2010 ∼ 2009 4 GV) with an increase of about a factor 3 with respect to July . 2008 , above 50 GV the agreement between PAMELA and AMS-02 proton 5 23th 2007 3.3 GV3.3 GV 4.2 GV4.2 GV 6.2 GV6.2 GV 10 GV10 GV 16 GV16 GV 30 GV30 GV 0.4 GV0.4 GV 0.5 GV0.5 GV 0.7 GV0.7 GV 0.8 GV0.8 GV 1.0 GV1.0 GV 1.3 GV1.3 GV 1.7 GV1.7 GV 2.1 GV2.1 GV 2.7 GV2.7 GV were collected. The high statistic allowed to sample the proton fluxes over shows the proton intensity at different rigidities (normalized to July 2006) measured 8 1 3 2 7

2006

Time-dependent proton intensities (normalized to July 2006) measured by PAMELA between 0.5 1.5 2.5 10 2006] Sept to [Norm Flux Proton × As showed in Figure Figure with the AMS-02 results. Now, an excellent agreement can be noticed also at low rigidities (e.g., fluxes is within 2%. However, belowulation this effects. rigidity, In the order measurements to differs because comparewith the of the PAMELA solar proton data mod- fluxes collected below between 50 Mayresponding GV, 2011 a to and new AMS-02 November analysis 2013, published was i.e. spectrum. performed the time Figure period cor- Figure 7: July 2006 and May 2014. Eachsatellite point or represents to a the off-line exclusion of sudden transient from thenon operation as of solar flares. either theduring PAMELA solar instrumentation events or were theenced satellite. excluded from at Furthermore, the the time analysis. lowest periods 2006. rigidity At The (0 higher major rigidities the modulation solartime-independent effects modulation within effects are the decrease experi- and experimental above uncertainties. 30consequent The GV minimum the 23rd modulation proton solar conditions flux minimum for is activity CRsthat and were the unusual the 24th (e.g. solar see cycle [ wouldcontinued begin until in the early end 2008. of Instead 2009from solar when the minimum PAMELA beginning measured modulation of the conditions the highest space cosmicintensity age. ray showed From proton 2010, a spectrum as decrease the up solarsolar to activity cycle started the to beginning was increase, of reached. the 2013, proton trend After when as the mid a maximum 2014, consequence activity of the of the lowest solar the energy activity 24th protons decrease. showed again an increasing The PAMELA Experiment: A Cosmic Ray Experiment Deep Inside the Heliosphere which approximate typical cosmic condition. Hence,origin very useful and information propagation for of understanding cosmic the rays in the Galaxy can beby derived. PAMELA from the beginning of thethan data-taking, 2 in July 2006, until Septembera 2014 [ Carrington Rotation (period of 27.27 days). Holes in the presented data are due to periods of PoS(ICRC2017)1091 , 21 Mirko Boezio ]. 400 Rigidity [GV] 23 300 Rigidity [GeV] 200 100 results from a constant fit on the flux ratio 0 polarity cycles such as 23, when 60 3 50 9 40 PAMELAPAMELA AMS-02AMS-02 30 5 GeV) an increase of the ratio was observed up to the end . 0.003 20 ± , present the first clear indication of the evolution of drift effects 9 ]. Only statistical errors are showed. The agreement between PAMELA = 0.995 16 0 P 10 9 ]). During so-called A < 0 5 - 1 and 1 - 2 8 . 20 7 (0 6 9 5 4 The PAMELA proton flux evaluated between May 2011 and November 2013 compared with 1 1.1 0.9 1.05 0.95 0.85 1.15 resulting from a constant fit to the flux ratio between 3 and 50 GV). 0 6000 8000

Strong evidence of charge-sign dependent solar modulation was provided by PAMELA mea- In the complex sun magnetic field the dipole term nearly always dominates the magnetic field of the solar wind. A The results show a time dependence of the positron to electron ratio. In the first two energy On top of the time dependence, a charge sign dependence of the solar modulation is expected.

12000 10000 14000

3 PAM / AMS / PAM

Flux Flux s sr GV) sr s [(m R ] GV

×

× ]. These data, shown in Figure 2 -1 2.7 2.7 surements of the positron to electron ratio, performed between July 2006 and December 2015 [ is defined as the projection of this dipole on the solar rotation axis. the heliospheric magnetic field ischarge directed particles toward undergo drift the motion Sun mainly inalong from the the the heliospheric northern current sheet. to hemisphere, the Positively negatively charged equatorialThe particles regions drift situation and mainly reverses outwards in opposite when directions. theHence, solar the magnetic charge-sign field dependence introduces changes a its 22-years polarity cycle. at each solar maximum. 22 during different phases of the solarmalized activity and to the the dependence values on measured particle betweenthe rigidity. July time Data and interval were December during nor- 2006. which The the process red of shaded polar area field represents reversal took place [ of 2009. During this time period positrons at Earth increased about 20% more than electrons. For intervals of Figure Figure 8: recent AMS-02 measurement [ and AMS-02 is excellent along the whole energy range. P between 3 and 50 GV. see P The gradients and curvatures presentcharge in sign the (e.g. HMF induce see drift [ motions that depend on the particle The PAMELA Experiment: A Cosmic Ray Experiment Deep Inside the Heliosphere PoS(ICRC2017)1091 ]. 23 where 9 Mirko Boezio 2016 2016 2016 2016 Time [Year] Time [Year] Time [Year] Time [Year] 2015 2015 2015 2015 A>0 A>0 A>0 2014 2014 2014 2014 10%. can be interpreted in terms of particle 2013 2013 2013 2013 9 ∼ A<0 A<0 A<0 2012 2012 2012 2012 decreased slowly to reach a minimum value at 4 10 2011 2011 2011 2011 2010 2010 2010 2010 0 GeV) this increase was 2009 2009 2009 2009 . 5 - 5 . 2008 2008 2008 2008 PAMELA 2.5 GeV - 5.0 GeV PAMELA 0.5 GeV - 1.0 GeV 0.5 GeV - 1.0 GeV PAMELA - 2.5 GeV PAMELA 1.0 GeV 2007 2007 2007 2007 1 1 1 0 2 2 2 80 60 40 20 1.8 1.6 1.4 1.2 0.8 1.8 1.6 1.4 1.2 0.8 1.8 1.6 1.4 1.2 0.8

The positron to electron ratios normalized to July - December 2006 measured at Earth by the

Norm to Jul-Dec 2006 2006 Jul-Dec to Norm /e e Norm to Jul-Dec 2006 2006 Jul-Dec to Norm /e e Norm to Jul-Dec 2006 2006 Jul-Dec to Norm /e e Tilt Angle [Degree] Angle Tilt

+ + + - - - In the context of this charge-sign dependent modulation, the tilt angle of the wavy heliospheric current sheet is the Until the middle of 2013 the ratio remained constant and slowly increased up to the middle of The trends in the observational data shown in Figure 4 most appropriate proxy for solar activity. Bottom panel: the tilt angle as a function of time. the third energy interval (2 drifts. For the period 2006 to 2009, the tilt angle 2014 when a sudden rise was observed up to late 2015 for the first two panels of Figure Figure 9: PAMELA experiment for three different energypoints intervals. to guide The the colored eye. lines The provide shaded connection area among corresponds the to the period with no well defined HMF polarity [ positrons increased respectively about 80%observed and for 50% the more highest than energy electrons. interval,electrons. where This The the sudden sudden positrons rise rise increased measured is only during not reversal about this of period 20% the appears more HMF. to than be a consequence of the polarity The PAMELA Experiment: A Cosmic Ray Experiment Deep Inside the Heliosphere PoS(ICRC2017)1091 ]. 6 became were the − e 10 / Mirko Boezio + ], AMS-02 [ 5 e 0) the positrons decreased. This 27 − > e 0 magnetic polarity A / 4 + < e 0 to A ], Aesop [ Energy [GeV] < 26 A 3 ]), January-December 2015, along with 6 AMS-02 (2011 - 2013) PAMELA (2006 - 2009) PAMELA (2011 - 2013) PAMELA (2015) CAPRICE94 (1994) HEAT94+95 (1994-1995) AMS-01 (1998) CLEM (1999) CLEM (2000) CLEM (2006) . During this ], AMS-01 [ 9 25 2 0 solar cycle. 11 > 0 solar cycle in the 90’s. ], CAPRICE94 [ 24 > 1 ] refer to the previous A 26 , 25 , ] from the previous A 24 -1 26 , ]), May 2011-November 2013 (as AMS-02 results [ 10 7 × 25

5 The PAMELA positron fraction for three time periods: July 2006-December 2009, (solar min- 0.1 0.2

, 0.05 0.15

Positron Fraction e Fraction Positron ) +e /(e

+ + 24 - PAMELA data are currently under analysis to study the temporal variation of additional parti- The charge-sign dependence introduced by drift motion is also visible in Figure The results from [ cycle, positrons drifted towards the Earthencountering mainly the through the changing equatorial wavy regions current of sheet,polar the while regions heliosphere, electrons of drifted the inwards heliosphere mainlypositron through and flux the were therefore consequently increased less relatively more influenceduntil than by the the the end electron current flux of sheet. withflux 2009. a also The decreasing decreased From proportionally tilt 2010 faster angle than onwards,continued the until the electron increased flux tilt solar and angle the activity ratio influenced increased both sharply fluxes so equally and that the the ratio positron positron fractions measured byshown. PAMELA in A various good agreement time cansame periods be time and noticed period. by between other PAMELA Moreover, andments the experiments AMS-02 [ positron are results fraction taken measured over in the 2015 draws near to the measure- cle species, focusing in particular on the solar modulation of GCR helium nuclei fluxes. Figure 10: imum, as in [ other recent measurements: HEAT94+95 [ the end of 2009 as shown in the bottom panel of Figure steady. From the end of 2012,until the the solar beginning magnetic of field 2014. had After gonegradually this into started turbulent a to reversal drift reversal phase phase, inwards (from through which theelectrons lasted polar started regions to of drift the heliosphere inwards toproportionally through the more the Earth than equatorial while for regions the electrons. so that the positron flux increased The PAMELA Experiment: A Cosmic Ray Experiment Deep Inside the Heliosphere PoS(ICRC2017)1091 -class 40% . ]. Table M 2 GeV/n) − 32 ]. ∼ Mirko Boezio 35 - and , X 34 events which also rep- th and 14 th ]. Such phenomena can last up to several ]. The helium and proton intensities show a 33 36 ]. This kind of uncertainty involves both low 12 29 , -class), and with full halo CMEs except for the 2011 28 C ]. 30 3 GeV/n. Solar helium nuclei (up to 1 GeV/n) and protons (up to ∼ ]. Since then, several other SEP events were measured by PAMELA [ 31 GeV range start a nuclear cascade through the Earth’s atmosphere that can be observed by 80 MeV/n to ∼ ∼ On top of the long-term solar modulation, short-term modulation effects also occur. For ex- In addition to the SEP event observed by PAMELA on December 13 2006, a significant For- PAMELA fills the largely unexplored energy gap between the particles detected in space (be- In addition to modulate the GCR energy spectra, the Sun contributes to the particle intensities Recurrent short-term GCR decreases have also been measured in association with the passage reports the list of the 28 major SEP events observed by PAMELA between 2006 July and 2014 ample, the near Earth GCR intensityronment. is In greatly particular, modified interplanetary by transients transientsudden phenomena such suppression in as of the CMEs GCR solar can intensity envi- induce near Forbush the decreases, Earth i.e. [ bush decrease was observedpassed when Earth. the PAMELA instrument full-halo measured the CME effectrigidity of produced range this from transient by 400 in the the MV GCR to solarstatistics intensity 20 in allowed event GV. the The to reached rigidity perform and reconstructioncomponents: a accuracy and rigidity protons, the helium dependent high nuclei collected study and of electrons [ the for various CR September 06, the 2012 July 08 and the 2013 October 284.2 events (partial Short-term halo variation CMEs). in the galactic cosmic ray intensity low few hundreds of MeV) and particlesobservation detected of at SEPs ground occurred level in (above few late GeV). 2006 First with PAMELA the December 13 September. For each event,along the with class/location the information related about CME the speed source and flare width. are All displayed, events were associated with energy particles measured inenergetic situ phenomena called and Ground the Level Enhancements. higherin These the energy are produced populations when which solardetectors protons lead at ground to level, particularly such asby neutron ordinary monitors, galactic as cosmic an rays increase above [ the background produced resent the first direct measurementfrom of SEPs in space withwere a recorded [ single instrument in1 the energy range flares except for the 2013 September 30 ( days and suppress the GCR intensity measured during quite Sun condition of about 30% in the heliosphere emitting a population offew particles GeV. with These energy solar ranging from energetic a particles few(CME). are tens associated of These keV with to events solar a inject flares andevent large coronal to amounts mass event of ejection and nuclei it isSun into accelerates heavily space, particles linked at whose to low the composition altitudeslayers through production varies magnetic of mechanisms from reconnection its that or atmosphere take higher (like place. in thean the corona) Whether outermost admixture through the coronal of mass the ejection-driven shocks, two, or perhaps is still unclear [ of Co-rotating Interaction Regionsleading (CIRs). edges of high-speed Such solar wind regions streamsthe of originating preceding from slow compressed coronal solar holes , wind, and are interacting formed a with well at known the cause of periodic CR decreases [ The PAMELA Experiment: A Cosmic Ray Experiment Deep Inside the Heliosphere 4.1 Solar Particle Events PoS(ICRC2017)1091 Mirko Boezio H H H H H H H H H H H H H H H H H H H H 157 N.A. N.A. N.A. N.A. N.A. N.A. N.A. Width CME 861 N.A. N.A. N.A. N.A. N.A. N.A. N.A. 1179 1402 1830 2145 1203 1267 1774 1042 1341 1255 2175 2508 2684 1884 1582 1828 1497 1631 2003 1466 Speed W90 W90 W90 W90 N.A. N.A. N.A. N.A. N.A. N.A. > > > > S12E82 N14E02 N17E27 N09E12 S15W11 S20W34 S06W23 S06W46 S21W54 S13W59 S17W74 S13W88 Location N17W29 N28W21 N27W71 N17W66 N11W76 N13W75 Flare 13 C1.3 N.A. N.A. N.A. N.A. N.A. N.A. X1.2 X4.9 X1.6 X3.4 X1.5 X2.1 X1.7 X5.4 X1.1 X1.4 M5.1 M7.3 M2.5 M5.3 M8.7 M7.9 M5.1 M6.9 M7.7 M6.5 M5.0 Class Date 2012 Jul 12 2012 Jul 19 2012 Jul 23 2012 Jul 06 2012 Jul 08 2014 Jan 06 2014 Jan 07 2012 Jan 23 2012 Jan 27 2011 Jun 07 2013 Oct 28 2014 Sep 01 2014 Sep 10 2013 Sep 30 2014 Feb 25 2011 Sep 06 2011 Sep 07 2014 Apr 18 2013 Apr 11 2006 Dec 13 2006 Dec 14 2011 Mar 21 2012 Mar 07 2012 Mar 13 2013 Nov 02 2011 Nov 04 2013 May 22 2012 May 17 SEP Event 6 7 8 2 3 4 5 9 # 1 21 22 23 24 25 26 27 28 10 11 12 13 14 16 17 18 19 20 15 List of the major SEP events observed by PAMELA between 2006 July and 2014 September. Table 1: For each event, thelated CME class/location speed information (km/s) abouthttps://cdaw.gsfc.nasa.gov/CME_list/sepe/. and the width source (deg, flare or “H” are in displayed, case along of with full the halogood CMEs). re- agreement for Flare/CME both data theaverage are amplitude a and from faster the recovery recovery time time. withThis On respect effect to could the be protons contrary interpreted and electrons as helium show athe nuclei on charge GCRs with sign a dependence during introduced similar their by amplitude. addition drift propagation motions to through that the affect the temporal heliosphere variationof produced during by about a the 13 negative CME polarity days propagationperiodicity cycle. in was heliosphere, lasted observed a In for in periodicity about the twovariation proton was months and compared and helium with had flux the athe after the mean SW the temporal velocity, amplitude the evolution Forbush of proton of decrease. abouttween density, the the 7%. the GCR solar This HMF temporal This wind variation intensity temporal (SW) andof and parameters prominent some others. structures like specific of SW A compressed features correlation plasma who was in could the found point heliosphere be- to like the CIR. passage However, since the he- The PAMELA Experiment: A Cosmic Ray Experiment Deep Inside the Heliosphere PoS(ICRC2017)1091 Mirko Boezio ]. ], on solar modulation of GCR deuterons 40 38 (2013) 3 400 days. This effect was also reported by the 10 ∼ 14 (2017) (2012) 011103 ]. 37 (2014) 121101. 108 (2013) 081102 (2007) 296 113 (2009) 105023 (2014) 323 27 111 (2001) 973 11 Nuovo Cimento 544 (2009) 607 559 (2008) 362 458 456 Phys. Rev. Lett. Phys. Rev. Lett. Phys. Rev. Lett. Phys. Rept. Nature New J. Phys. Astropart. Phys. Living Reviews in Nature Astrophys. J. We would like to thank E. C. Christian, G. A. de Nolfo, M. S. Potgieter, J. M. Ryan and It was the 15th of June of 2006 when the PAMELA satellite-borne experiment was launched Finally, a distinct feature was found in the low energy (80 MeV - 10 GeV) proton fluxes ] and on effects due to the Earth’s magnetosphere [ [8] M. Boezio et al., [9] M. S. Potgieter, [6] L. Accardo et al., [7] O. Adriani et al., [2] O. Adriani et al., [3] O. Adriani et al., to appear[4] in O. Adriani et al., [5] M. Ackermann et al., [1] P. Picozza et al., 39 [10] S. Torii et al., [11] J. Chang et al., S. Stochaj for fruitful collaborationknowledge partial on financial the support from study The ofgramma Italian Space solar PAMELA Agency - physics (ASI) attivitá under and the scientifica solarfrom program Deutsches di modulation. "Pro- fur analisi Luft- We und dati Raumfahrt ac- in (DLR),Research The Council, fase Swedish The E". National Russian Space Space Board, We Agency The (Roscosmos) also Swedish and acknowledge Russian support Science Foundation. References [ from the Baikonur cosmodromemaking in high-precision Kazakstan. measurements of Then, thea charged for new component era nearly of of ten precision the years,of studies cosmic in production, PAMELA radiation cosmic acceleration has opening rays and been and propagationIn challenging of our addition cosmic basic to vision rays the of inpresented results the the results mechanisms discussed galaxy on in and lithium this in and the paper, beryllium heliosphere. at isotopes the [ conference the PAMELA Collaboration 5. Conclusions and acknowledgments worldwide network of Neutron Monitors but,observed to in space our at knowledge, this it low isthe energies. heliosphere. the first This However, it time effect is could that worth be itEarth noticing linked that has intersected to the been the larger the IMF proton turbulent lines fluxes environment comingfrom were of the from observed when intense Jupiter the Jupiter hinting magnetosphere to [ a possible, surprising, contribution measured by PAMELA with a peculiar period of The PAMELA Experiment: A Cosmic Ray Experiment Deep Inside the Heliosphere liospheric current sheet (HCS) isbe often incorporated crossed into in the the CIR slowintensity along variation solar and with wind the the preceding HCS slow a crossing solar cannot CIR, be wind, and excluded. a may correlation between this periodic PoS(ICRC2017)1091 (2017) this this Mirko Boezio this conference (2015) 114 (2007). 798 2017 012034 798 (2004) 744 (2017) Astrophys. J. (1976) 91 603 2014 581 15 207 (2017) (2004) 267 44 (1990) 600 (2013) 53 111 (2014) 221102 (2008) 261104 (2017) (2017) 345 this conference (1997) L191 (200) 55 (2009) 181101 (2015) 171103 (2015) no.21, 211101 175 (2016) 241105 Astrophys. J.. 113 93 101 (2011) 102 (2000) 653 482 (2000) 10 102 114 115 116 Astrophys. J. Nature 742 532 this conference 484 (2011) 69 (2017) 332 Proc. 30th Intl Cosmic Ray Conf., Merida this conference this conference Astrophys. J. Journal of Physics: Conference Series Phys. Rev. Lett. Phys. Rev. Lett. Phys. Rev. Lett. Phys. Rev. Lett. Phys. Rev. Lett. Space Science Reviews Astrophys. J. Science Phys. Rev. Lett. Astrophys. J. Phys. Lett. B Brazilian Journal of Physics Space Science Reviews this conference Space Science Reviews (2017) (2017) conference PAMELA experiment”, PAMELA experiment”, PAMELA space experiment”, the PAMELA magnetic spectrometer”, conference experiment.”, [39] S. Koldobskiy et al., “Solar modulation of the galactic deuteron spectrum measured with the [36] R. Munini et al., “Short-term variation in the galactic cosmic ray[37] intensity measuredM. with Ricci the et al., “Effect of the Jupiter magnetosphere on the[38] Cosmic RayW. protons Menn measured et with al., the “Cosmic-Ray Lithium and Beryllium Isotopes in the PAMELA-Experiment”, [40] V. Mikhailov et al., “Measurements of electron and positron fluxes below the geomagnetic cutoff by [28] T. Mathews and D. Venkatesan, [26] J. Alcaraz et al., [27] J. Clem and P. Evenson, [29] G. A. Bazilevskaya, [31] O. Adriani et al., The PAMELA Experiment: A Cosmic Ray Experiment Deep Inside the Heliosphere [12] F. Aharonian et al., [24] S. W. Barwick et al., [25] M. Boezio et al., [30] D. V. Reames, [32] M. Mergé et al., “PAMELA measurements[33] of solarH. energetic particle V. Cane, spectra”, [34] C. W. Barnes and J. A.[35] Simpson, I. G. Richardson, [13] A. A. Abdo et al., [14] M. Aguilar it et al., [17] M. Aguilar et al., [18] M. S. Potgieter, [20] S. E. S. Ferreira and M. S. Potgieter, [15] O. Adriani et al., [16] M. Aguilar et al., [21] O. Adriani et al., [22] R. Munini et al., “Ten years of positron and electron solar[23] modulation measured byX. the Sun PAMELA and J. T. Hoeksema and Y. Liu and J. Zhao, [19] B. Panico et al., “Time dependence of the proton and helium flux measured by PAMELA”,