21 ECRS , Kosice, 12/09/2008

Trapped charge particles measurements in the radiation belt by PAMELA instrument

Vladimir V. Mikhailov (MEPHI)

for

PAMELA collaboration

PAMELA experimentSatellite ResursDK №1:

The launch 15/ 06/ 2006;

Elliptical orbit : 350- 610km with inclination ~700

3 axis stabilization. Information about the satellite

attitude is stored on-line every ~1-180sec

Count rate of top PAMELA counter: low energy ~MeV protons rate.South Atlantic Anomaly (SAA) is clearly seen Pitch angle count rate in SAA.

See Poster of V.Malakhov P2.08 for more details

Altitude 350 – 400km, L=1.10-1.15

Altitude 550 – 600km, L=1.10-1.15

Determination of SAA’s boundaries:For determination of SAA boundaries the protons count from geomagnetic coordinates L,B was plotted for different altitudes and rigidities.

Protons R<500MevProtons 0.5<R<1GevProtons 1<R<1.5GevProtons 1.5<R<2GevProtons R>2.5Gev

B,Gaus B,Gaus

L -shell

Altitude 350-400 km

PAMELA can observe low edge of the inner radiation belt

0.17<B<0.21Gs, L shell 1.-1.7

Size of SAA for altitudes between 350-600km

Altitudes changes from 350 to 600kmLongitude

Lat

itu

deB<0.21Gs, L-shell <1.2

Proton spectrum in SAA, polar and equatorial regions

Proton spectrum in SAA for different B values

B>0.24Gs

B=0.23Gs

B=0.21Gs

B=0.19Gs

L<1.2

PAMELA and AP8min model

AP8 model line was normalized at 0.1GeV to data point

L=1.2 B=0.2Gs

Pitch-angle distribution in SAA

1/(m2*sr*sec*MeV)

Data of August-September, 2006

Observed distribution of protons with E~200-250MeV

Distribution corrected for angular efficiency of the instrument, (red line)

Proton spectrum in SAA for different pitch-angles

Kinetic Energy,Gev

1/(m2*sr*sec*MeV)

August-September, 2006

Pitch angle distribution in SAA for different energies1/

(m2*

sr*s

ec*M

eV)

August-September, 2006

Pitch-angle, deg.

Solar modulation

• Proton spectra since August 2006 till September of 2007: effect of solar modulation is visible.

• Low energy proton intensity is increasing with time

The difference of solar modulation parameter. Since 07.2006 till 02.2008. Data of Apatity neutron monitor are taken from http://jag.cami.jccbi.gov/Helio/helio.asp (provided by Eduard Vashenuk)

Galactic proton spectra

trapped protons: modulation or boundary effects?

• It looks the flux of trapped high energy protons is decreasing in period of observation since August 2006 till September 2007

• It needs more study because conditions of observation vary month by month

0.2 0.20.5 0.5

Galactic proton spectra Trapped proton spectra

Trapped He and electrons

• electrons:

He nuclei

Observation at L<1.2. Preliminary data of PAMELA for August 2006. Comparison of data B>0.24Gs (equatorial subcut-off data) and B<0.21Gs (SAA data)

Conclusion

• 1) PAMELA observed geomagnetically trapped particles near lower edge of SAA 0.18<B<0.21Gs in wide energy range from ~100MeV

• 2) New data could be used to improve empirical and theoretical models of the inner radiation belt such as , AP-8, etc