Roberta Sparvoli, Sif 2001 - Milano La missione NINA: misure di raggi cosmici di bassa energia in orbita terrestre Roberta Sparvoli per la Collaborazione

Roberta Sparvoli, Sif 2001 - Milano

La missione NINA: misure di raggi cosmici di bassa

energia in orbita terrestreRoberta Sparvoli

per la Collaborazione WiZard-NINA*

* Univ. of Tor Vergata and INFN, Rome, ItalyMoscow Engineering Physics Institute, Moscow, RussiaUniv. of Trieste and INFN, Trieste, ItalyUniv. of Bari and INFN, Bari, ItalyUniv. of Firenze and INFN, Firenze, ItalyINFN Laboratori Nazionali di Frascati, Frascati, ItalyIROE CNR, Firenze, Italy


Balloon

MASS1 (89)MASS2 (91)

TS93CAPRICE94

CAPRICE97CAPRICE98

Scientific activitySatellite/Space Station

Life Science SilEye-1 SilEye-2

Cosmic rays NINANINA-2PAMELA

rays AGILE ALTEAGLAST

1990

1995

2000

2005


The Cosmic Ray radiation


Galactic Cosmic RaysGCRs 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 RaysThey 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

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:


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

• 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| R0-5/4 (4 R0-3)-1/4 ;


South Atlantic AnomalyAbove 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 particlesAlbedo 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. Trappedwith 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.


Objectives of the mission 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-1

Launch: 10 July 1998Launch: 10 July 1998Base Baikonur (Kazakhstan) Zenith launcher

First scientific data: 31st August 1998.

End of the mission: 13th April 1999.

2.000.000 events taken

Collaboration WiZard-NINA: Italy (INFN) - Russia (MEPhI)

Russian satellite RESURS-01 n.4RESURS-01 n.4::

PERIOD ~ 100 min

ALTITUDE ~ 840 km INCLINATION 98.7 deg. MASS 2500 kg


The instrument NINAThe detector (D1)Basic element: a silicon wafer 6x6 cm2, 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).


Total weight = 40 kgPower = 40 WInternal structure:

Whole structure is housed in a cylindrical aluminum vessel (300 m thick), filled up with N at 1.2 atm.


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.


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 NINA-1 worked always in Full Containment, whereas NINA-2 adopted also the Non-Containment operating mode.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.


Performance of NINA-1

Geometrical factor 10 cm2sr

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


Isotope identificationMethod of the Residual Range:the mass M of the isotope with charge Z is given by: 1/(b-1)

M = a[Eb - (E - E)b] Z2 x with E the total energy released in the detector, and aa and bb parameters optimized by fit. xx is a particle path opportunely tuned, with energy deposit EE. . Flight data in agreement with data taken on ground


Orbit analysis

Mid-latitudes:Trapped

Albedo

Polar regions:GCRSEPACR


GCR flux measurements

Performed in the solar quiet period: December 1998-March 1999, during passages over the polar cups.

- Particle relative abundancesrelative abundances estimated;- Spectra of 44HeHe, 1212CC and 1616OO reconstructed.


The comparison with other instruments is consistent

Particle relative abundances

Particle fluxes


SEP events observationsPeriod of observation: November 1998 -- April 1999. 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.


4He energy spectraNINA energy window for 4He: 10--50 MeV/n.Galactic

backgroundFlux (E): A E- + B(E)

Power-law

spectrum


3He/4He ratio

3He 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 3He/4He ratio 3 greater than the solar coronal value (~4x10-4).


2H/1H and 3H/1H ratioNINA 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.

Only upper limits for the 3H/1H ratio.

In 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].


Particles trapped in the SAA

Period of observation: November 1998--April 1999Passages into SAA: 7 revolutions/daySAA L-shell<1.2 and B<0.22 G

Local pitch-angle loc in SAAcorresponds to an equatorial pitch-angle < 0 > 75°.

At Resurs altitudes particles detected are permanently trapped (mirror points higher than atmosphere).

|sin 0| R0-5/4 (4 R0-3)-1/4


E1-Etot and mass reconstruction

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].

Roberta Sparvoli, Sif 2001 - MilanoL-shell 1.18—1.22, B<0.22 G

3He and 4He flux in SAA (3He) = 2.30 ± 0.08 in [10--50 MeV] (4He) = 3.4 ± 0.2 in [10--40 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 3He content.

Roberta Sparvoli, Sif 2001 - MilanoL-shell 1.18—1.22, B<0.22 G

2H and 3H flux in SAAThe 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.

2H/1H ~ 0.01 NINA 10 MeV/n2H/1H ~ 10-3 [Selesnick & Mewaldt, 1996]

3H/2H ~ 0.2 NINA 10 MeV/n3H/2H ~ 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.


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 http://wizard.roma2.infn.it/nina

Documents

Roberta Sparvoli, Sif 2001 - Milano La missione NINA: misure di raggi cosmici di bassa energia in orbita terrestre Roberta Sparvoli per la Collaborazione