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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
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