Emergence of hard X-rays at weak nonstationary processes in active regions
Tóm tắt
Using Suzaku and Reuven Ramaty High Energy Solar Spectroscopic Image (RHESSI) spacecraft data, we study the characteristics of X-ray emission of weak flares at energies when this emission is generated by fluxes of accelerated electrons. Of the 105 events recorded by a broadband monitor of the entire sky (WAM/Suzaku, with an effective area of ~800 cm2 in the energy range from 50 to 300 keV), we consider 64 B1to C3-class flares. The spectra of these events up to 30 keV are built from RHESSI data. We consider some examples of simultaneous recordings of weak flares occurring from 2005 to 2007. The radiation fluxes measured by WAM/Suzaku at 100 keV have been found to be consistent with those expected from the one-parameter approximation of spectra of the nonthermal radiation recorded by RHESSI at lower energies. The average spectral slope for all events under consideration is 4.30 ± 0.15; i.e., these rare events are significantly stricter than the majority of subflares. This can serve as proof of the fact that the particle acceleration in weak flares is more effective than was previously assumed. As in powerful events, these processes occur in the close vicinity of spots or in places where the neutral line separates hills with a large magnetic field strength.
Tài liệu tham khảo
Christe, S., Hannah, I.G., Krucker, S., McTiernan, J., and Lin, R.P., RHESSI microflare statistics. I. flare-finding and frequency distributions, Astrophys. J., 2008, vol. 677, pp. 1385–1394.
Endo, A., Minoshima, T., Morigami, K., et al., A catalog of Suzaku/WAM hard X-ray solar flares, Publ. Astron. Soc. Jpn., 2010, vol. 62, no. 2, pp. 1341–1349.
Grigor’eva, I.Yu., Livshits, M.A., Rudenko, G.V., and Mysh’yakov, I.I., Active regions near the recent solarcycle minimum: Relation between plasma heating and electrical current, Astron. Rep., 2013, vol. 57, no. 8, pp. 611–621.
Grigor’eva, I.Yu. and Livshits M.A., Weak solar flares with a detectable flux of hard X-rays: Specific features of microwave radiation in the corresponding active regions, Geomagn. Aeron. (Engl. Transl.), 2014, vol. 54, no. 8, pp. 1045–1052.
Ishikawa, S., Krucker, S., Ohno, M., and Lin, R.P., Suzaku/WAM and RHESSI observations of non-thermal electrons in solar microflares, Astrophys. J., 2013, vol. 756, no. 2, 143.
Kopp, R.A. and Pneuman, G.W., Magnetic reconnection in the corona and the loop prominence phenomenon, Sol. Phys., 1976, vol. 50, p. 85.
Lin, R.P., Dennis, B.R., Hurford, G.J., Smith, D.M., Zehnder, A., Harvey, P.R., Curtis, D.W., Pankow, D., Turin, P., and Bester, M., et al., The Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI), Sol. Phys., 2002, vol. 210, no. 1, pp. 3–32.
Livshits, M.A. and Kashapova, L.K., Relationship between nonthermal and gasdynamic processes in powerful solar flares, Geomagn. Aeron. (Engl. Transl.), 2012, vol. 52, no. 7, pp. 892–901.
Pisarenko, N.F. and Mirzoeva, I.K., X-ray flares and a possible scenario of weak solar flares, Cosmic Res., 2008, vol. 46, no. 1, pp. 90–93.
Sylwester, J., Kuzin, S., Kotov, Yu.D., Farnik, F., and Reale, F., SphinX: A fast solar photometer in X-rays, J. Astrophys. Astron., 2008, vol. 29, pp. 1–5.
Ulyanov, A., Kuzin, S., and Bogachev, S., The statistical analysis of energy release in small-scale coronal structures, Abstract Book of the 40th COSPAR Scientific Assembly, August 2–10, 2014, Moscow, Russia, Abstract E2.6-18-14.
Yamaoka, K., Endo, A., Enoto, T., Fukazawa, Y., Hara, R., Hanabata, Y., Hong, S., Kamae, T., Kira, C., Kodaka, N., Kokubun, M., et al., Design and in-orbit performance of the Suzaku wide-band all-sky monitor, Publ. Astron. Soc. Jpn., 2009, vol. 61, no. SP1, pp. S35–S53.