Abstract and keywords
Abstract (English):
We have studied properties of sustained gamma fluxes having quantum energies of >100 MeV at different stages of flares with 1-min temporal resolution (Fermi/LAT). The most probable process of emergence of high-energy gamma-quanta during the impulsive phase of flares (6 events) has been confirmed. Acceleration of particles, produced by flare energy release (at dissipation of current sheet), occurs when they interact with a shock front of a coronal mass ejection (CME), which develops in the same active region at the same time. Nuclear interactions of accelerated protons (>500 MeV) with plasma ions lead further to the emergence of high-energy gamma-quanta. We have established that the interaction between a flare flux and a high-speed CME during the flare impulsive phase occurs within fairly limited periods — from 2 to 16 min. In the events considered, we have found a direct connection between maximum gamma flux F max (γ > 100 MeV) and CME velocity. High maximum values of gamma fluxes are typical of the flare impulsive phase: 3.5·10⁻⁴ cm⁻²s⁻¹ ≤ F max (γ > 100 MeV) ≤ 1.3·10⁻² cm⁻² s⁻¹. At the same time, the value F max (γ > 100 MeV) = 0.013 cm⁻²s⁻¹ was the highest for the events observed by Fermi/LAT from 2008 to 2017. During the development of CMEs moving with a supersonic speed, shock waves are formed which are the major power source of accelerated particles during the main phase of gradual flares. In some cases, however, the impact of shock waves on particle acceleration is the greatest in the short impulsive phase. To reveal parameters most effectively influencing the generation of high-energy gamma-ray emission, we have compared 17 flare events. The most significant parameter proved to be the time interval of joint action of flare process and CME shocks. We have established that during simultaneous development of flare process and CME attendant on the flare, the most efficient particle acceleration occurs which gives rise to maximum fluxes of high-energy gamma-quanta.

flares, coronal mass ejection, particle acceleration, gamma-ray emission
Publication text (PDF): Read Download

1. Ackermann M., Allafort A., Baldini L., Barbiellini G., Bastieri D., Bellazzini R., et al. Fermi-LAT observations of high-energy behind-the-limb solar flares. arXiv:1702.00577v1 [astro–ph.SR] 2 Feb 2017. 14 p.

2. Akimov V.V., Afanassyev V.G., Belousov A.S., Blokhintsev I.D., Kalinkin L.F., Leikov N.G., et al. Observation of high energy gamma-rays from the Sun with the GAMMA-1 telescope (E>30 MeV). Proc. 22nd ICRC. 1991, vol. 3, pp. 73–76.

3. Altyntsev A.T., Banin V.G., Kuklin G.V., Tomozov V.M. Solnechnye vspyshki [Solar Flares]. Moscow, Nauka Publ., 1982. 246 p. (In Russian).

4. Kurt V.G., Yushkov B.Yu., Kudela K., Galkin V.I. High-energy gamma emission of solar flares as an indicator of acceleration of high-energy particles. Proc. 31st National Conference on Cosmic Rays. Moscow, MSU, 2010, pp. 1–5. (In Russian).

5. Livshits M.A. Solar flares: observation results and gas-dynamic processes. Plazmennaya geliofizika [Plasma Heliophysics]. Moscow, Nauka Publ., 2008, vol. 1, pp. 60–81. (In Russian).

6. Priest E.R., Forbs T. Magnitnoe peresoedinenie. Magnitogidrodinamicheskaya teoriya i prilozheniya [Magnetic Reconnection. Magnetohydrodynamic Theory and Applications]. Moscow, Fizmatlit Publ., 2005. 591 p. (In Russian).

7. Golovko A.A., Kuklin G.V., Mordvinov A.V., Tomozov V.M. The role of shear motions in the production of a preflare situation. Contributions of the Astronomical Observatory Skalnate Pleso. 1986, vol. 15, pp. 243–250.

8. Gopalswamy N., Mäkela P., Yashiro S., Lara A., Xie H., Akiyama S., MacDowall R.J. Interplanetary type II radio bursts from Wind/WAVES and sustained gamma-ray emission from Fermi/LAT: evidence for shock source. Astrophys. J. Lett. 2018., vol. 868, L19, 8 p. DOI: 10.3847/2041-8213/aaef36.

9. Gopalswamy N., Mäkela P., Yashiro S., Lara A., Xie H., Akiyama S., MacDowall R.J. Fermi, Wind and SOHO observations of sustained gamma-ray emission from the Sun. URSI AP–RASC 2019, New Delhi, India, 09–15 March 2019. URL: https://arxiv.org/ftp/arxiv/papers/1810/1810.08958.pdf (accessed 01.04.2019).

10. Grechnev V.V., Kurt V.G., Chertok I.M., Uralov A.M., Nakajima H., Altyntsev A.T., Belov A.V., Yushkov B.Yu., Kuznetsov S.N., Kashapova L.K., Meshalkina N.S., Prestage N.P. An extreme solar event of 20 January 2005: properties of the flare and the origin of energetic particles. Solar Phys. 2008, vol. 252, pp.149–177. DOI: 10.1007/s11207-008-9245-1.

11. Knizhnik K.J., Antiochos S.K., DeVore C.R., Wyper P.F. The mechanism for the energy buildup driving solar eruptive events. Astrophys. J. Lett. 2017, vol. 851, L17, 6 p. DOI: 10.3847/2041-8213/aa9e0a.

12. Li Y., Sun X., Ding M.D., Qiu J., Priest E.R. Imaging observations of magnetic reconnection in a solar eruptive flare. Astrophys. J. 2017, vol. 835, 190, 8 p. DOI: 10.3847/1538-4357/835/2/190.1.

13. Manchester W., Kilpua K.J., Liu Y.D., Lugaz N., Riley P., Török T., Vršnak B. The physical processes of CME/ICME evolution. Space Sci. Rev. 2017, vol. 212, pp. 1159–1219. DOI: 10.1007/s11214–017–0394–0.

14. Minasyants G.S., Minasyants T.M., Tomozov V.M. Features of the development of gamma-rays in a solar flare February 25, 2014. News National Academy RK, Phys.-Math. Ser. 2018, vol. 4, no. 320, pp. 15–21.

15. Murphy R.J., Dermer C.D., Ramaty R. High-energy processes in solar flares. Astrophys. J. Suppl. 1987, vol. 63, pp. 721–748.

16. Omodei N., Pesce-Rollins M, Longo F., Allafor A., Krucker S. Fermi-LAT observations of the 2017 September 10th solar flare. arXiv: 1803.07654v1 [astro-ph.HE]. 2018, 6 p.

17. Share G.H., Murphy R.J., Tolbert A.K., Dennis B.R., White S.M., Schwartz R.A., Tylka A.J. Characteristics of sustained >100 MeV ray-emission associated with solar flares. arXiv:1711.01511v1 [astro-ph.SR]. 2017a, 83 p.

18. Share G.H., Murphy R.J., Tolbert A.K., Dennis B.R., White S.M., Schwartz R.A., Tylka A.J. Characteristics of thirty second-stage >100 MeV γ-ray events accompanying solar flares. ApJS in review, arXiv 1711.01511v1. 2017b, 34 p.

19. Shibata K. Reconnection model of flares. Solar physics with radio observations. Proc. of Nobeyama Symposium. 1998, pp. 381–389. (NRO Report N 479).

20. Somov B.V. Plasma Astrophysics: Reconnection and Flares. New York, Springer, 2013, 504 p. DOI: 10.1016/ S02731177(97)00968-X.

21. Tylka A.J., Share G.H., Dietrich W.F., Murphy R.J., Ng C.K., Shea M.A., Smart D.F. Solar protons above 500 MeV in the Sun’s atmosphere and in interplanetary space. Report EGU General Assembly, Vienna, Austria 27 April — 02 May 2014. 2014. EGU2014-16847, 41 p.

Login or Create
* Forgot password?