Roberta Sparvoli, Sif Milano La missione NINA: misure di raggi cosmici di bassa energia in orbita terrestre Roberta Sparvoli per la Collaborazione WiZard-NINA* * Univ. of Tor Vergata and INFN, Rome, Italy Moscow Engineering Physics Institute, Moscow, Russia Univ. of Trieste and INFN, Trieste, Italy Univ. of Bari and INFN, Bari, Italy Univ. of Firenze and INFN, Firenze, Italy INFN Laboratori Nazionali di Frascati, Frascati, Italy IROE CNR, Firenze, Italy

Roberta Sparvoli, Sif Milano Balloon MASS1 (89) MASS2 (91) TS93 CAPRICE94 CAPRICE97 CAPRICE98 Scientific activity Satellite/Space Station Life Science SilEye-1 SilEye-2 Cosmic rays NINA NINA-2 PAMELA  raysAGILE ALTEA GLAST

Roberta Sparvoli, Sif Milano The Cosmic Ray radiation

Roberta Sparvoli, Sif Milano Galactic Cosmic Rays GCRs are a directly accessible sample of matter coming from outside the Solar System. The energy spectrum is a power-law for E > 1 GeV/n; at lower energy it is attenuated by the action of the Solar Wind ( solar modulation ). GCRs are produced in the primordial nucleosynthesis (light elements) or in explosions of supernova stars. At the end of their nuclear evolution, some stars explode as violent supernova event, dispersing most of the star's matter. Some of this material is accelerated to form cosmic rays. Particles are most probably accelerated by interactions with shocks waves from the supernova event.

Roberta Sparvoli, Sif Milano Anomalous Cosmic Rays They represent a sample of the very local interstellar medium. Have a lower speed and energy than GCRs. ACRs include He, O, Ne and other elements with high FIP. While interstellar plasma is kept outside the heliosphere by an interplanetary magnetic field, the interstellar neutral gas flows through the solar system. When closer to the Sun, its atoms undergo the loss of one electron in photo-ionization or by charge exchange. Once these particles are charged, the Sun's magnetic field picks them up and carries them outward to the solar wind termination shock. The ions repeatedly collide with the termination shock, gaining energy in the process. This continues until they escape from the shock and diffuse toward the inner heliosphere. Those that are accelerated are then known as Anomalous Cosmic Rays.

Roberta Sparvoli, Sif Milano Solar Energetic Particles Solar Flares : until the 90ies thought to be responsible of the most intense SEPs and geomagnetic storms. The Solar Flare is an explosive release of energy (both electromagnetic and charged particles) within a relatively small (but greater than Earth-sized) region of the solar atmosphere. Coronal Mass Ejections (CMEs): violent eruptions of coronal mass, known to be the very responsible of particle acceleration. Often, not always, associated to a flare. The fast CME explosion in the slow Solar Wind produces a shock wave which accelerates particles. Particles emitted in SEPS are a sample of matter coming from the solar corona. They are originated by:

Roberta Sparvoli, Sif Milano The influence of the Earth magnetic field Originated by electric currents running inside the Earth core. To a first approximation it is a dipolar field : -> Coordinates: 79°N, 70°W and 79°S, 110°E, reversed with respect to geographic Poles, about 11° inclined with Earth axis and shifted by 320 km. Latitude effect : the CR flux depends on the latitude, is higher at the poles than at the equator. Each latitude has a cut-off rigidity (p/z) below which no vertically arriving particles can penetrate.

Roberta Sparvoli, Sif Milano Trapped particles Drift : longitudinal. It is due to dishomogeneity of the field and variations of the gyroradius. Positive particles drift westward, negative eastward. Combination of 3 periodic motions: Gyration : a helix around the field line; Bounce : oscillation around the equatorial plane between almost symmetrical mirror points. Only small oscillations are possible, the mirror point cannot hit the Earth surface. Pitch-angle  0 : angle between p and B at the equator. Condition for trapping: |sin  0 |  R 0 -5/4 (4 R 0 -3) -1/4 ;

Roberta Sparvoli, Sif Milano South Atlantic Anomaly Above South America, about kilometers off the coast of Brazil, and extending over much of South America, the nearby portion of the Van Allen Belt forms what is called the South Atlantic Anomaly. This is an area of enhanced radiation caused by the offset and tilt of the geomagnetic axis with respect to the Earth's rotation axis, which brings part of the radiation belt to lower altitudes. The inner edge of the proton belt dips below the line drawn at 500 km altitude.

Roberta Sparvoli, Sif Milano Albedo particles Albedo particles are produced by cosmic ray interactions in atmosphere (40 km). They are rebound to space by the Earth magnetic field and have energies below the cut-off. According to pitch-angle, we can have: 1. Only one bounce: albedo 2. More than one bounce: quasi-trapped 3. Trapped with almost equal fluxes (Grigorov, 1977). Differences between albedo and trapped: - the origin traces back into atmosphere or ground level; - shorter flight time (from source to sink). - energy up to GeV.

Roberta Sparvoli, Sif Milano Objectives of the mission NINA Study of the nuclear and isotopic component of Galactic Cosmic Rays (GCR): H-Fe --> MeV/n in full containment H-Fe --> 10-1 GeV/n out of containment Study of Solar Energetic Particles (SEPs) in a long portion of the 23 solar cycle, and transient solar phenomena Study of particles trapped in the magnetosphere (in SAA) and albedo particles Study of Anomalous Cosmic Rays (ACRs) Mission organized in two steps

Roberta Sparvoli, Sif Milano The mission NINA-1 Launch: 10 July 1998 Base Baikonur (Kazakhstan) Zenith launcher First scientific data: 31 st August End of the mission: 13 th April events taken Collaboration WiZard-NINA: Italy (INFN) - Russia (MEPhI) RESURS-01 n.4 : Russian satellite RESURS-01 n.4 : PERIOD ~ 100 min ALTITUDE ~ 840 km INCLINATION 98.7 deg. MASS 2500 kg

Roberta Sparvoli, Sif Milano The instrument NINA The detector (D1) Basic element: a silicon wafer 6x6 cm 2, 380  m thick with 16 strips, 3.6 mm wide in two orthogonal views X -Y. 32 wafers arranged in 16 planes, 1.4 cm apart. The first two 150  m thick (to lower the energy threshold) and 8.5 cm apart (to improve the trajectory reconstruction).

Roberta Sparvoli, Sif Milano Total weight = 40 kg Power = 40 W Internal structure: Whole structure is housed in a cylindrical aluminum vessel (300  m thick), filled up with N at 1.2 atm.

Roberta Sparvoli, Sif Milano Positioning into Resurs D1: the detector, composed of 32 silicon layers and the electronics for signal processing; D2: the on-board computer, a dual microprocessor dedicated to data processing and to the selection of the trigger and the acquisition mode configuration; E: the interface computer, which rearranges the data coming from box D2 and delivers them to the satellite telemetry system; P: the power supply, which distributes the power supply to the different subsystems.

Roberta Sparvoli, Sif Milano Operating Modes Containment: - the strips 1 and 16 of each plane form the Lateral AC, always ON; - Plane 16 forms the Bottom AC, ON in normal operations. NINA-1 worked always in Full Containment, whereas NINA-2 adopted also the Non-Containment operating mode. Trigger: - the main trigger requires a particle to reach the first view of the second silicon plane, i.e. requires a particle to hit at least 3 silicon detectors.

Roberta Sparvoli, Sif Milano Performance of NINA-1 Geometrical factor 10 cm 2 sr Maximum aperture ± 34º Pointing accuracy 5º Time resolution 2  s Energy resolution (containment) 1 MeV Mass resolution H --> 0.1 amu He --> 0.15 amu

Roberta Sparvoli, Sif Milano Isotope identification Method of the Residual Range: the mass M of the isotope with charge Z is given by: 1/(b-1) M = a[E b - (E -  E) b ] Z 2  x ab  x  E. with E the total energy released in the detector, and a and b parameters optimized by fit.  x is a particle path opportunely tuned, with energy deposit  E. Flight data in agreement with data taken on ground

Roberta Sparvoli, Sif Milano Orbit analysis Mid-latitudes: Trapped Albedo Polar regions : GCR SEP ACR

Roberta Sparvoli, Sif Milano GCR flux measurements Performed in the solar quiet period: December 1998-March 1999, during passages over the polar cups. relative abundances - Particle relative abundances estimated; 4 He 12 C 16 O - Spectra of 4 He, 12 C and 16 O reconstructed.

Roberta Sparvoli, Sif Milano The comparison with other instruments is consistent Particle relative abundances Particle fluxes

Roberta Sparvoli, Sif Milano SEP events observations Period of observation: November April SEP events are identified by increases of at least one order of magnitude in the counting rate. Protons E>10 MeV 9 such increases have been recorded in this period. Other space instruments confirm the SEP detection. Some events are very close in time but show different characteristics.

Roberta Sparvoli, Sif Milano 4 He energy spectra NINA energy window for 4 He: MeV/n. Galactic background Flux (E): A E -  + B(E) Power-law spectrum

Roberta Sparvoli, Sif Milano 3 He/ 4 He ratio 3 He Background subtraction : Solar quiet BG: measured during passages over the polar cups in solar quiet periods. Secondary production: in the Al cover. About 10% of the solar quiet BG (estimations). SEP events with 3 He/ 4 He ratio 3  greater than the solar coronal value (~4x10 -4 ).

Roberta Sparvoli, Sif Milano 2 H/ 1 H and 3 H/ 1 H ratio NINA energy window for H isotopes: MeV/n. 2 H/ 1 H ratio : (3.9 ± 1.4) x averaged over all events, consistent with solar abundances. Only upper limits for the 3 H/ 1 H ratio. In a previous measurement (IMP-5): 2 H/ 1 H ratio : (5.4 ± 2.4) x 10 -5, in [ MeV/n ], averaged over several events [Anglin, ApJ, 198, 733, 1975].

Roberta Sparvoli, Sif Milano Particles trapped in the SAA Period of observation: November April 1999 Passages into SAA: 7 revolutions/day SAA  L-shell<1.2 and B<0.22 G Local pitch-angle  loc in SAA corresponds to an equatorial pitch-angle  75°. At Resurs altitudes particles detected are permanently trapped (mirror points higher than atmosphere). |sin  0 |  R 0 -5/4 (4 R 0 -3) -1/4

Roberta Sparvoli, Sif Milano E 1 -E tot and mass reconstruction The E 1 vs. E tot graph shows presence of H and He isotopes in SAA. Also 6 Li is visible. The mass reconstruction algorithm, after background subtraction, confirms the presence of ‘real’ H and He isotopes in Radiation Belts. 3 He is more abundant than 4 He [see also Wefel et al., 24 th ICRC 1995].

Roberta Sparvoli, Sif Milano L-shell 1.18—1.22, B<0.22 G 3 He and 4 He flux in SAA  ( 3 He) = 2.30 ± 0.08 in [ MeV]  ( 4 He) = 3.4 ± 0.2 in [ MeV] Reasonable agreement with data from MAST on SAMPEX [Cummings et al., AGU Fall Meeting, 1995] at L-shell=1.2, all averaged over local pitch-angles. Data are in agreement with models of proton interaction with the residual atmospheric helium [Selesnick and Mewaldt, 1996, JGR, 101, 19745]. The sum of He and O interaction sources in atmosphere seems to overestimate the 3 He content.

Roberta Sparvoli, Sif Milano L-shell 1.18—1.22, B<0.22 G 2 H and 3 H flux in SAA The 2 H and 3 H fluxes are compared with models based on atmospheric interaction and models combining the effect of atmospheric interaction and radial diffusion [Spjeldvik et al, 1997, 25th ICRC]. The global agreement is quite good. 2 H/ 1 H ~ 0.01 NINA 10 MeV/n 2 H/ 1 H ~ [Selesnick & Mewaldt, 1996] 3 H/ 2 H ~ 0.2 NINA 10 MeV/n 3 H/ 2 H ~ 0.05 [Spjeldvik et al, 1997]. Nevertheless a more detailed abundance analysis is not consistent with the existing models. For L-shell=1.2: SAMPEX results on deuterium [Looper et al., Radiation Measurements, 1996] were also higher than calculations.

Roberta Sparvoli, Sif Milano Conclusion NINA-1 flew one year in space with performance according to expectations; The analysis of Galactic Cosmic Rays, SEP events and particles in the SAA provided excellent results; Anomalous Cosmic Rays could not be detected owing to the solar modulation; The albedo particle analysis is still in progress; NINA-2 is continuing NINA-1 observations in a different period of the 23rd solar cycle; PAMELA will complement the NINA observations extending the energy range. Visit our web site