Physics of auroral phenomena : proceedings of the 39th annual seminar, Apatity, 29 February-4 March, 2016 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2016. - 167 с. : ил., табл.

PROTON ACCELERATION IN THE SOLAR FLARE I.M . P o dgo rny1, A.I. Podgorny2 1 Institute f o r A stronom y RAS, Moscow , Russia 2Lebedev P hysical Institute RAS, Moscow , Russia Abstract. 100 years of research of high-energy particles coming from distant regions of space have not led to an understanding of the physics of acceleration of these particles. The most popular acceleration mechanisms are associated with shock waves. However, the possible acceleration mechanisms of cosmic rays in the shock waves are only hypotheses. Naturally, the discovery of sources of protons with energies up to 20 GeV, generated by the Sun, gives us hope for the opportunity to clarify the mechanism of the cosmic rays generation. The imported data about solar cosmic rays now obtained in PGI from the worldwide network of neutron monitors. The new information about the mechanism of proton acceleration in the Sun has been obtained by comparing the data of neutron monitors with the results of measurements on the GOES devices. Some analysis of GOES measurements have been reported by the authors in the Apatity seminar in 2015. The association of a proton event with a particular flare is beyond doubt. Measurements on GOES devices indicate propagation of high-energy protons from the flares on the western part of the solar disk without collisions. These protons move along helical magnetic field lines. Another part o f the protons comes to the Earth's magnetosphere with the solar wind velocity. The protons from flares on the back side of the Sun can also come to the Earth's magnetosphere. The front of proton flux from eastern flares comes to Earth with a delay of several hours. The series of 2-3 weeks long proton events consisting of several large proton events are observed two - three times in the 11 year cycle of solar activity. Nature of the trigger for series of proton events is not clear. Introduction. Explosive release of energy occurs in the solar corona above the active region at a solar flare. Just a few tens of minutes, the energy stored in the magnetic field of the current sheet [1-3] heats plasma with the density of ~ 10n cm 3 up to the temperature 3-5 keV. The main manifestations of the flare: pulses of thermal and beam (hv>100 keV) X-ray, coronal mass ejections, causing a shock wave, visible, ultraviolet, and microwave radiation at different frequencies, pulses of relativistic protons (solar cosmic rays), etc. Some of these events are manifested in some flares, but the other phenomena may be absent. Here we consider the generation of pulses of cosmic rays with energies up to 20 GeV. Solar energetic proton measurements provide information which is not available in the study of cosmic rays coming from distant regions of space. The shock waves are the most popular mechanisms of cosmic ray acceleration. Proton acceleration in shock waves is also considered by many authors as a mechanism o f the solar cosmic rays generation [4-7]. The shock wave is formed by a supersonic coronal mass ejection. However, any data on particle acceleration in a shock wave are based on some arbitrary assumptions. The acceleration of protons at reflection from magnetic inhomogeneities in the solar wind is also considered [8]. Measurements made on the world network of neutron monitors [9-11] showed that the front pulse of relativistic protons of the flares that have occurred in the western part of the solar disk (so-called "prompt" component) begins to register through time At -1 5 min after the pulse of thermal X-ray emission of the flare onset. This delay is determined by the time o f flight of the particles along the lines of the interplanetary magnetic field Archimedes spiral. Not all of the protons accelerated during a flare enter the interplanetary space. Some of them hit the surface of the Sun, causing a nuclear reaction with gamma-radiation release. Since, as a rule, the duration of gamma-radiation caused by nuclear reactions in the Sun, is no more than ten minutes, it can be argued that the duration of generation of relativistic particles are also not more than ten minutes. However, neutron monitors on the Earth show the relativistic proton flow during the several days. Such delayed protons can not belong to the direct stream from the flare. They come to Earth from the flare as a result of transfer by the solar wind or diffusion. The main result considered in [9-11] is the fundamental difference spectrum of fast and delayed proton flux components. The fast component enters the Earth's orbit only from the flare occurring in the western part of the solar disk. The prompt component consists of particles passing in small pitch angles along the lines of the interplanetary magnetic field without collision. It has the exponential spectrum -exp (-W/W0). Apparently, it is a spectrum of particles emitted from the source. After 15-20 minutes the velocity distribution recorded on the Earth's orbit becomes isotropic, and the spectrum becomes of a power type W'r. This delayed proton flux can last several days, and its distribution becomes a diffusive. The values of W0 are not much different for the different events are observed in the range 0.5-1 GeV, у is within 4-6. Numerical simulations have shown [20] that introduction of the magnetic turbulence leads to scattering of protons, and anisotropic velocity distribution at a later stage becomes isotropic. The conditions for the relativistic particles generation of solar cosmic rays are existed in the current sheet in the singular magnetic field line vicinity [2, 3]. In a particular case it is a line of zero magnetic field. The electric field - VxB / с in the current sheet occurs at the plasma inflow in the current sheet and reconnection of magnetic field lines Here, V -is the velocity of plasma inflow into the sheet, that is the reconnection velocity, В is the magnetic field of "P h y sic s o f A u r o r a l P h e n o m e n a " , P r o c . XXXIX A n n u a l Sem in ar, A p a tity , pp. 60-65,2016 © P o l a r G e o p h y s ic a l I n s t i t u t e , 2016 P o l a r G eophysical I nstitute 60