1. A Relation between Solar Flare Manifestations and the GLE Onset
Victoria G. Kurt 1*, Boris Yu. Yushkov1**, Anatolii Belov2, Ilya Chertok2,
Victor V.Grechnev3
1 Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, , Russia
2 Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation, Troitsk, Moscow Region, , Russia.
3 Institute of Solar-Terrestrial Physics SB RAS, Irkutsk , Russia * **

2. The main goal of this work is to determine the onset time of proton acceleration to high energies during large solar flares.
R = 2-4 R☼
Reames, Ap.J., 2009, 693, 812

3. Solar flare gamma radiation with energies
> 0.5 MeV is the direct indicator of accelerated particle appearance in the corona.
Electrons generate bremsstrahlung with energy up to energy of these electrons themselves.
Protons with energies MeV generate gamma-line radiation of excited nuclei as well as the neutron capture line 2.2 MeV.
Protons accelerated up to energies above 300 MeV generate the high-energy gamma radiation as a result of neutral pion decay. This emission is characterized by wide spectral maximum near 70 MeV and is originated in the density matter of the solar atmosphere.

4. Pion-decay Gamma-Ray Emission Spectrum
3 June 1982
28 October 2003

5. The Onset Time of the Pion-Decay Gamma-Ray Emission of Major Solar Flares (Poster 0287) V. Kurt, B. Yushkov, V. Grechnev
24 May 1990
28 October 2003

6. Acceleration of protons up to sub-relativistic energies in major flares, determined from observations of the pion-decay gamma-ray emission starts temporally close to the main flare energy release.
This conclusion can be used
in analyses of solar particle events and GLE onset,
to find the onset time of acceleration in events when the pion-decay emission was not observed.

7. We studied 42 GLE events and associated flares since 1972 (GLE 25)
The time of the main flare energy release To was determined
The GLE onset time Tonset was found.
First protons arrived the Earth could be observed by one or several neutron monitors (Kurt et al., Astron. Lett., 2010, 36, 520).
and therefore the onset time of proton acceleration up to high energies.

8. Assumptions
Accelerated protons can escape the Sun immedeately after their acceleration.
2. Path length of protons propagating with a small pitch angle without scattering could be shorter than a nominal length on magnetic field line.

9. Nominal length of field line (1.0) = 1.1 AU
From Pei et al., Ap.J., 2006, 614, 1222.

10. Given the spread in particle mean free paths and velocities, the delay time of the first recorded particles with respect to observed To time can be estimated as 1–8 min.

11. Determination of To and Tonset.
22 November 1977
15 April 2001

12. The Main Result

13. Distribution of difference between T0 and Tonset.
The Main Result-2
Distribution of difference between T0 and Tonset.
Time delay DT of the GLE onset vs heliolongitude of associated flare.

14. Conclusions
1. First solar protons can be observed at 1 AU with time delay 1-8 min after observation of electromagnetic emissions which manifest the main flare energy release.
2. Acceleration of high-energy protons (> 300 MeV) starts near the time of the main flare energy release.

15. Thank you for attention!
This work was supported by the Russian Foundation for Basic Research (project and )