The laboratory was founded in 1964 as a sector of theoretical research, under the leadership of N. I. Osipov. In 1967, the sector was headed by G. F. Krymsky. In 1967  the sector was transformed into a theoretical department. In 1987  E. G. Berezhko was elected as Head of the department. In 1993, the department was transformed into the laboratory of the theory of space plasma. Since 1993  S. I. Petukhov is Head of the laboratory

Research areas:

– propagation and acceleration of cosmic rays in the Galaxy

– generation of solar cosmic rays by shock waves in the solar atmosphere and propagation in the heliosphere

– dynamics of the intensity of high-energy galactic cosmic rays in transient solar wind regimes of various scales

– large-scale solar wind disturbances and their influence on the course of geomagnetic processes

Results

Dynamics of cosmic ray fluctuations

Acceleration of charged particles by shock waves in the heliosphere

Nonlinear theory of cosmic ray acceleration in supernova remnants

Acceleration of charged particles in shear plasma flows

Regular acceleration of charged particles on shock fronts

Dynamics of cosmic ray fluctuations

1.The “Cyber-FORSHOCK” robotic system for prediction of extreme events of  space weather in real- time on the Internet in advance of  ~1 day has been created.

2. A precursor of growth phase of the current (No. 24) 11-year cycle with  the advance time of ~1 solar revolution has been revealed.

3. In the 22nd solar activity cycle a “low-frequency drift” of the 11-year cycle period was detected, which made it possible to predict an “extraordinary failure” of the 11-year cycle at the end of the 23 cycle, i.e. a “phase catastrophe”, according to G. V. Kuklin’s terminology , approximately 3 years in advance (ISTP SB RAS Preprint, 1982).

 Acceleration of charged particles by shock waves in the heliosphere

As shown by numerous experiments carried out aboard spacecraft, shock waves resulting from solar flares produce intense flows of suprathermal particles (ions), the energy of which significantly exceeds the thermal energy of plasma particles when the solar wind flows around the planetary magnetospheres, as well as when the solar wind interacts with the interstellar medium (see Figure 1).

The discovery of process of regular acceleration ( G.F.Krymskii, Soviet Physics Doklady 22, 327,  1977) made it possible to understand the nature of these phenomena and describe them in detail. For this purpose, ShICRA has developed a self-consistent nonlinear theory of particle acceleration by shock waves in the heliosphere, which consistently takes into account the main physical factors affecting the acceleration process, namely, the geometry of system and its evolution in time, the generation of Alven waves by accelerated particles. The implementation of the theory required the development of a complex

 numerical algorithm, with no analogues currently . The calculations performed on the basis of this theory are in good agreement with the available experimental data (see Fig. 2, 3 for the case of near-Earth and interplanetary shock waves, respectively). An actual problem of solar physics and solar-terrestrial physics is to find out the nature of solar cosmic rays (SCR), namely, the intense fluxes of charged particles that occur during sporadic events on the Sun. There are indications that the so-called “gradual” increases of SCR fluxes are generated in the solar corona at the fronts of shock waves generated by coronal ejections of the matter. The application of theory developed in ShICRA to this case made it possible to achieve a good agreement of the theoretical predictions with the experiment (see Fig. 4).

Anomalous cosmic rays (ACR), or more precisely, the anomalous component of cosmic rays, whose existence was established in the early 1970s, got their name due to the unusual shape of their energy spectrum in the energy range ε = 1-100 MeV/nucleon, which is radically different from the spectrum of galactic cosmic rays. According to the generally accepted point of view, anomalous cosmic rays are the result of acceleration of ionized atoms of the local interstellar medium captured by the solar wind on a heliospheric shock wave that limits the area of the supersonic solar wind stream (see Fig.1). The high energy content of ACRs leads to the fact that they become an important dynamic factor that significantly affects the structure of shock front.

ShICRA has developed a nonlinear theory of ACR acceleration that consistently takes into account the inverse effect of accelerated ACRs on the structure and position of the heliospheric shock wave (E.Berezhko, L.Ksenofontov, Astron.  Letters 31, 1(2005)). Calculations carried out on its basis have shown that the process of ACR acceleration and properties of the shock wave are sensitive to the rate of injection of captured ions during acceleration (Fig.5). According to theoretical calculations, the size (radius) of the heliospheric shock wave Rs = 82 – 96 AU corresponds to the expected values of injection rate n ~ 10-2 and concentration of the solar wind (near the Earth’s orbit) n0 = 5-7 cm-3, that is in  a good agreement with the available measurement results carried out with  the Voyager-1 spacecraft (see Fig.5).

Nonlinear theory of cosmic ray acceleration in supernova remnants

One of the main problems of modern astrophysics is the problem of cosmic ray origin. It is known that, for energy reasons, supernova explosions are the only class of objects capable of providing the observed energy density of cosmic rays, on condition that there is a mechanism for transfer of  ~10% of the kinetic energy of the ejected supernova shell to cosmic rays.

 РИСУНОК

Such a mechanism was discovered in 1977 by G. F. Krymsky and called as a  mechanism of regular acceleration of charged particles at shock wave fronts. In this process, the particles, scattering on the inhomogeneities of the magnetic field, repeatedly cross the shock wave front and each time their energy increases.

For a detailed study of process of cosmic ray acceleration in supernova remnants, a nonlinear kinetic theory was developed at ShICRA (E. G. Berezhko et al.). It is based on the numerical solution of cosmic ray transport equation together with gas-dynamic equations of the medium. The theory allows us to study the evolution of the supernova remnant, spectra of accelerated particles, chemical composition of cosmic rays, as well the properties of non-thermal radiation generated by them. The efficiency of developed numerical calculation method was several orders of magnitude greater than similar methods used by other groups to solve the problem.

It is shown that the form of calculated spectra of chemical elements in the composition of cosmic rays, for which there are measurements, does not contradict the experiment.

Based on the comparison of results of the theory with the spectra of TeV gamma radiation from individual supernova remnants of Cassiopeia A and RX J1713. 7-3946, it is established that supernova remnants are indeed the main source of galactic cosmic rays.

Acceleration of charged particles in shear plasma flows

Shear flows (see Fig.1), which are characterized by the fact that the velocity of medium u is directed everywhere in one direction, and the magnitude of velocity u is a function of coordinate transverse to this direction, is a fairly common phenomenon in the space plasma. Plasma flows of such a structure occur, for example, when the solar wind flows around the planetary magnetospheres, as well in areas occupied by high-speed solar wind flows, when “jets” of plasma appear against the background of the “normal”, “calm” solar wind, having significantly higher speeds than the environment. As evidenced by numerous experiments carried out aboard spacecraft, in the areas occupied by the shear currents of the solar wind, the intense flows of superthermal particles are always observed, the energy of which exceeds the characteristic thermal energy of plasma by several orders of magnitude. This indicates that the process (or mechanism) of acceleration is realized in the shear flows of collisionless plasma, which transforms the energy of directed motion of plasma into the energy of small fraction of accelerated particles.

РИСУНОК

Fig. 1. Shear flow of the medium. The blue arrows show the direction and magnitude of the velocity of the medium; the red polyline is a trajectory of  superthermal  charged particle experiencing scattering on inhomogeneities of the magnetic field frozen into the medium .

РИСУНОК

Fig.2. Relativistic jets emanating from the core of active galaxy.

A striking example of jet flows are relativistic jets flowing into the environment at speeds close to the speed of light from the nuclei of active galaxies (see Fig. 2). The availability of a large number of accelerated high-energy charged particles in these jets is evidenced by the fact that the non – thermal radiation generated by these particles is “visible” at cosmological distances in all wavelength ranges-from the radio to the gamma range inclusive.

At ShICRA the existence of so-called frictional acceleration process  has been established, which makes it possible to understand the nature of high-energy particle fluxes in the areas occupied by shear plasma flows (E.G.Berezhko, JETP Lett. 33, 416 (1981)). Its essence consists in the fact that a high-energy long-range particle, scattering on the inhomogeneities of the field frozen into  the medium, “feels” the difference of velocities of the medium at every two consecutive scattering points, due to which the average momentum of particles p increases in time, according to the law

УРАВНЕНИЕ

Where τ  is the average time between scatterings, a is a number of the order of unity. The physical situation here is similar to that which occurs when the cold gas comes into contact with  the hot one. Due to paired collisions, cold gas molecules acquire energy on average. In the case of shear flows of collisionless plasma, the role of hot gas is played by scatterers, and the role of cold gas is played by long – range particles undergoing acceleration.

Regular acceleration of charged particles on shock fronts

A characteristic property of space plasma is the presence of processes in it that lead to the generation (acceleration) of fast charged particles with the energy much higher than thermal. Fast accelerated particles are directly registered by devices installed aboard spacecraft in the various areas of interplanetary space, which is filled with solar wind plasma. Their energy in some cases reaches several gigaelectronvolts, that is several orders of magnitude higher than the characteristic thermal energy of the plasma. One of the examples of such kind is the solar cosmic rays that are generated during solar flares.

The presence of a large number of relativistic charged particles has been established using the methods of radio, X-ray and gamma-ray astronomy in various astrophysical objects, such as supernova remnants, radio galaxies and a number of others. One of the most striking manifestations of acceleration processes are galactic cosmic rays.

Especially intense flows of superthermal particles are observed at the shock wave fronts. The most general reason is that the dominant form of energy in the interplanetary and interstellar medium is the kinetic energy of supersonic large-scale plasma flows. The interaction of these flows with the environment leads to the formation of shock waves, at the fronts of which the energy of directed motion is transformed into the internal energy of the plasma. A significant part of this energy is represented in the form of superthermal particles, the spectrum of which, having a power-law form, extends to energies of  many orders of magnitude higher than the average thermal energy of the plasma.

Correct understanding of the nature of populations of high-energy particles in shock wave fronts became possible due to the discovery of regular acceleration process made at ShICRA  (G.F.Krymskii,  Soviet Physics Doklady 22, 327,1977). The essence of this process is illustrated in Fig. 1, where the nature of movement of a fast particle in the vicinity of hock front is schematically shown.

The particle undergoes quasi-elastic scatterings on inhomogeneities of the magnetic field on both sides of the shock front, which causes the diffusive nature of its propagation, which makes it possible to repeatedly cross the shock front. The motion of medium, especially the fact that the speed of flow of the undisturbed medium _u1 is higher than the speed of outflow from the front after passing the shock front, causes a continuous increase of the particle energy.

An important feature of the regular acceleration process is the fact that the spectrum of accelerated particles, i.e. the dependence of their distribution function f(p) on the momentum p, has  the following universal power-law form:

ФОРМУЛА

and it does not depend on any properties of the medium and is entirely determined by a single parameter σ  – the degree of compression of the substance in the shock front. In a series of works carried out at ShICRA (see Berezhko E.G., Krymsky G.F. Phys.Usp.154  49 (1988); Berezhko E.G., YolshinV.K, Krymsky G.F., Petukhov S.I. 1988, Generation of cosmic rays by shock waves, Novosibirsk: Nauka), properties of the regular acceleration process were investigated and its determining role in the generation of high-energy particle fluxes in a number of astrophysical objects, in particular, the spectrum of galactic cosmic rays formed in supernova remnants was shown. Acceleration of cosmic rays on supernova remnants (Video illustration from the NASA WEB page)