Results from the NINA and NINA-2 Space experiments Roberta Sparvoli * For the WiZard-NINA Collaboration * 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

Past,Present and Future Projects MASS-89, 91, TS-93, CAPRICE 94-97-98 PAMELA GLAST WiZard Program NINA-2 NINA M 89 M 91 TS 93 C 94 C 97 GLAST C 98 PAMELA … 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 ... SILEYE-1 NINA NINA-2 SILEYE-3 SILEYE-4 SILEYE-2 SILEYE-2 SILEYE-1 ALTEA: SILEYE-4 ALTEINO: SILEYE-3

The Cosmic Ray radiation

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.

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.

Solar Energetic Particles Particles emitted in SEPS are a sample of matter coming from the solar corona. They are originated by: 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.

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.

Trapped particles Origin:high energy CR interactions in atmosphere, producing neutrons and then protons and electrons. Also Solar Wind and influences of the ionosphere. Inner Radiation Belt: protons with E up to hundreds MeV. Mean life time: years. It extends to 1.5 RE. Outer Radiation Belt: electrons with E of a few MeV. Mean life time: days. It extends to 4.5 RE. Death: distortions in the magnetic field (also due to solar activity) bring particles to jump to different field lines which go down to dense atmosphere. Collisions. Also collisions among themselves.

South Atlantic Anomaly Above South America, about 200 - 300 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.

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. > one bounce: quasi-trapped 3. Trapped with almost equal fluxes (Grigorov, 1977).

Objectives of the missions NINA Study of the nuclear and isotopic component of Galactic Cosmic Rays (GCR): H-Fe --> 10-200 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

The mission NINA Russian satellite RESURS-01 n.4: Launch: 10 July 1998 PERIOD ~ 100 min ALTITUDE ~ 840 km INCLINATION 98.7 deg. MASS 2500 kg Launch: 10 July 1998 Base Baikonur (Kazakhstan) Zenith launcher First scientific data: 31st August 1998. End of the mission: 13th April 1999. 2.000.000 events taken

The mission NINA-2 Italian satellite MITA: Launch: 15 July 2000 PERIOD ~ 100 min ALTITUDE ~ 450 km INCLINATION 87.3 deg. MASS 200 kg Launch: 15 July 2000 Base Plesetsk (Russia) Cosmos launcher First scientific data: 21th July 2000 5 trasmissions per day End of the mission: 15th August 2001 >10^7 triggers taken

The instrument NINA The detector (D1) Basic element: a silicon wafer 6x6 cm2, 380 mm 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 mm thick (to lower the energy threshold) and 8.5 cm apart (to improve the trajectory reconstruction). Total weight = 40 kg Power = 40 W

Isotope identification Method of the Residual Range: the mass M of the isotope with charge Z is given by: 1/(b-1) M = a[Eb - (E - DE)b] Z2 Dx with E the total energy released in the detector, and a and b parameters optimized by fit. Dx is a particle path opportunely tuned, with energy deposit DE. Flight data in agreement with data taken at ground

Orbit analysis Polar regions: Mid-latitudes: GCR Trapped SEP Albedo ACR Mid-latitudes: Trapped Albedo

GCR flux measurements Particle relative abundances Particle fluxes Performed in the solar quiet periods, during passages over the polar cups. Particle relative abundances Particle fluxes The comparison with other instruments is consistent V. Bidoli etal., "In-orbit performance of the space telescope NINA and GCR flux measurements“, ApJS, 132 (2001), 365.

SEP events observations NINA 9 SEP events: Analysis complete NINA-2 10 SEP events: Analysis still in progress A. Bakaldin et al, “Light Isotope Abundances in Solar Energetic Particles measured by the Space Instrument NINA”, accepted by APJ NINA NINA-2

SEP by NINA: 3He and 4He NINA energy window for 4He: 10--50 MeV/n. SEP events with 3He/4He ratio 3 s greater than the solar coronal value (~4x10-4).

2H/1H and 3H/1H ratio NINA energy window for H isotopes: 9--12 MeV/n. 2H/1H ratio: (3.9 ± 1.4) x 10-5 averaged over all events, consistent with solar abundances. A previous measurement (IMP-5): 2H/1H ratio: (5.4 ± 2.4) x 10-5, in [10.5--13.5 MeV/n], averaged over several events [Anglin, ApJ, 198, 733, 1975]. First measurement of deuterium in SEPs! Only upper limits for the 3H/1H ratio.

Particles trapped in the SAA The E1 vs. Etot graph shows presence of H and He isotopes in SAA. Also 6Li is visible. The mass reconstruction algorithm, after background subtraction, confirms the presence of ‘real’ H and He isotopes in Radiation Belts. 3He is more abundant than 4He [see also Wefel et al., 24th ICRC 1995].

3He and 4He flux in SAA g (3He) = 2.30 ± 0.08 in [10--50 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. L-shell 1.18—1.22, B<0.22 G 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 3He content.

2H and 3H flux in SAA The 2H and 3H 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. First measurement of tritium trapped in radiation belts! L-shell 1.18—1.22, B<0.22 G A more detailed abundance analysis is not consistent with the existing models. New measurements are needed as input to the models (NINA-2). A. Bakaldin et al., “Geomagnetically trapped light isotopes observed with the detector NINA”, accepted by JGR

Albedo particles: protons The three hydrogen isotopes have been clearly detected and their spectra measured. 2H and 3H contribution to the 1H flux is not negligible ! ( ~10%)

NINA and NINA-2 vs altitude: Proton flux NINA and NINA-2: Albedo component comes from interaction of high energy CR with atmosphere, and only marginally affected by solar modulation. NINA – AMS: Energy spectrum at low energy not simply an extrapolation by a power-law from AMS. < 100 MeV spectrum flattens. NINA and NINA-2 vs altitude: the proton flux at 10 MeV does not depend appreciably on the altitude along a fixed L-shell, in the range from 200 km to 850 km. V. Bidoli et al., “Energy spectrum of secondary protons above the atmosphere measured by the instruments NINA and NINA-2 “, subm. to Annales Geophysicae

Albedo particles: helium 3He & 4He Flux: Power-law with g = 0.8±0.2 (3He) g = 1.5±0.2 (4He) NINA and NINA-2: Average value of 3He/4He ~1.5 [10-40 MeV/n]. NINA and AMS: ratio increasing with energy. V. Bidoli et al., “Isotope composition of secondary hydrogen and helium above the atmosphere measured by the instruments NINA and NINA-2”, subm. to GRL

Conclusions NINA and NINA-2 flew in space with performance according to expectations; The analysis of Galactic Cosmic Rays, SEP events, particles in the SAA and albedo particles provided very good results; Anomalous Cosmic Rays could not be detected due to solar modulation; NINA and NINA-2 results smoothly connect to the ~ GeV observations of the WiZard balloon program (cfr. E. Vannuccini, this morning); PAMELA will complement the NINA observations extending the energy range to hundreds of GeV (cfr. M. Pearce, tomorrow);. Visit our web site http://wizard.roma2.infn.it