1. Study of 20 January 2005 solar flare area by certain gamma-ray lines
Evgenia Troitskaia1, Irene Arkhangelskaja2, Weiqun Gan3, Jian Wu3
1Lomonosov Moscow State University Skobeltsyn Institute of Nuclear Physics, Russia
2National Research Nuclear University "MEPhI", Moscow, Russia
3Purple Mountain Observatory, Nanjing, China

2. Extreme solar event of 20 January 2005
Importance: X7.1/3B
Location: N14W61
Begin-peak-end: 06:36UT-07:01 UT-07:26 UT
CME, Proton event, GLE (ground level event)
Strong gamma-ray emissions: bremsstrahlung,
nuclear narrow + broad lines

3. CORONAS-F /SONG-D/AVS-F
[Arkhangelskaja, Kotov et al., SEE-2007, Greece, JASR: 43 (2009), 589–593]
Спектр гамма- излучения солнечной вспышки 20
января 2005 г.
RHESSI
[Share, Murphy,
AGU Monograph Series,
165, ,
2006]
RHESSI
[Share, Murphy, AGU Monograph Series,165, , 2006]

4. Data: registered from detector SONG-D by the AVS-F onboard CORONAS-F, up to 140 MeV
In the present work we analyze the time profile of MeV γ- line from neutron captures by hydrogen nuclei, we also use narrow de-excitation gamma lines from 12C at 4.44 MeV and 16O at 6.13

5. Radiative neutron capture by hydrogen:
De-excitation lines:

6. Modeling: Monte-Carlo simulation of processes with energetic neutrons, making allowance for:
possible energetic neutron escape from the Sun;
gravitational neutron-Sun interaction;
thermal motion of decelerated neutrons;
neutron decay;
neutron deceleration in elastic collisions with hydrogen nuclei, with due account for the energy and angular dependencies of cross-sections for np-scattering;
neutron captures by hydrogen 1H, with the production of deuterium 2H and gamma-quantum of MeV;
non-radiative neutron absorption on 3He
gamma-ray absorption in the solar atmosphere in dependence on solar flare central angle;
time profile of initial neutron production;
initial neutron spectra;
altitude dependence of surrounding matter density.
Details see: Kuzhevskij et al. (1998)

7. Using the time profile of 2.223 MeV line, we plan to derive:
● the model of altitude profile of solar atmosphere
● =n(3He)/n(1H);
● αT or s (spectral index of energetic protons)
5 density models are
used in the
calculations

8. The modeling with different parameters

9. Which one is the best: for the averaging through full time of 2
Which one is the best: for the averaging through full time of MeV line
Least square sums
results: αТ=0.1, m=5, κ=(1.4±0.15)10-4

10. Effect of Angular distribution of neutrons
Least square sums
Downward isotropic distribution versus
fan-shaped distribution: the later is worse than
the former

11. For better coincidence, three time intervals are separately fitted
II: κ=1.4×10-4,
αT=0.03,
m=5
III: κ=2.0×10-4,
αT=0.1,
Considering the evolution of the parameters,
the fitting looks quite well!

12. Conclusions By fitting the time profile of 2.223 MeV line, we got:
At the first stage the quiet non-disturbed atmosphere is more plausible; then the density in the deep atmosphere becomes increased;
The spectrum of accelerated protons becomes hardening with time;
The content of 3He changes from at the rising phase to at the decay phase;
For angular distribution of neutrons, downward isotropic distribution is better than fan distribution.