Leonty I. Miroshnichenko

IMPULSIVE, STOCHASTIC, AND SHOCK WAVE ACCELERATION OF RELATIVISTIC PROTONS IN LARGE SOLAR EVENTS OF 1989 SEPTEMBER 29, 2000 JULY 14, 2003 OCTOBER 28, AND 2005 JANUARY 20

Using the data from neutron monitors and applying various techniques, the parameters of relativistic solar protons (RSPs) outside the magnetosphere are currently being derived by several research groups. Such data, together with direct proton measurements from balloons and spacecraft, allow the determination of particle energy spectra near the Earths orbit in successive moments of time. Spectra of RSPs in a number of large solar events tend to indicate the existence of multistep acceleration at/near the Sun. In this paper, we study the generation of RSP by neutral current sheet, stochastic, and shock-wave acceleration, within the framework of two-component concepts for ground level enhancements (GLEs) of solar cosmic rays (SCRs). Our analysis is extended to large solar events (GLEs) of 1989 September 29, 2000 July 14, 2003 October 28, and 2005 January 20. We found two different particle populations (components) in the relativistic energy range: a prompt component (PC), characterized by an early impulselike intensity increase, hard spectrum and high anisotropy, and a delayed component, presenting a gradual late increase, soft spectrum and low anisotropy. Based on a two-source model for SCR spectrum formation at the Sun, we carried out theoretical calculations of spectra in the sources for both components. We conclude that the processes in neutral current sheet, together with stochastic acceleration in expanding magnetic trap in the solar corona, are able to explain the production of two different relativistic components. Shock acceleration in the presence of coronal mass ejection (CME) fits fairly only the nonrelativistic range of the SCR spectrum, but fails in the description of relativistic proton spectra, especially for the PC.

On the formation of relativistic particle fluxes in extended coronal structures

We analyze neutron monitor data of solar cosmic rays in order to obtain information about their sources. We use three methods for these data analysis. As result, we obtain a set of evidences for two separate solar cosmic rays sources that we call as prompt and delayed components. We attempt here to substantiate a two sources scenario for the generation of both components. For the prompt component source, we suggest regular acceleration in a neutral current sheet. For the delayed one, we propose acceleration by magnetosonic wave turbulence.

Large Ground Level events in solar cycle 22 and some peculiarities of relativistic proton acceleration.

Some of the Ground Level Enhancements of Solar Cosmic Rays (SCR) recorded by neutron monitors during solar cycle 22 are analyzed. The events appeared in series, and their occurrence rate in 1989-1991 was a factor of 4 larger than the average value (approximately equal to 1/yr) for the total observation interval (since 1942). The events of Sept. 29 and Oct. 24, 1989 proved to be the more intensive. The analyzed events show no peculiarities as to the distribution of the T1/2 parameter, whereas the shape of the profile of some events is notable for a two peak structure. The latter implies the possibility of a two component SCR ejection from two different sources in the solar atmosphere. For the event of Sep. 29 we have estimated the ejection rigidity spectrum of protons to be D solar (R) = (1-2) 10(32)R(-2.9) Gv-1 at R greater than or equal to 1 Gv. As to its proton flux, this event proved to be by 1-2 orders less intensive than the well known event of Feb. 23 1956.

Solar particle acceleration by slow magnetosonic waves

Abstract Particle acceleration by slow magnetosonic waves (SMW) has been systematically disregarded. We examine the real possibility of this mode for acceleration of solar electrons on basis to a quantitative analysis. Evaluations of the times scales involved in the phenomenon allow us to determine the conditions in the solar atmosphere where resonant acceleration by the slow MHD mode may occur.

Summary and Conclusions: Problems and Prospects

In the above Chapters the author attempted to summarize a copious data on solar cosmic rays (SCR) and relevant solar, interplanetary and geophysical observations, to demonstrate the importance of solar energetic particles (SEPs) for a number of fundamental astrophysical and geophysical problems. Their applications to the tasks of practical astronautics also have been briefly discussed. One of the main goal of this book was to describe different (sometimes contradictory) approaches to the interpretation of those data and to the simulation of space plasma processes involved, at the contemporary (up-to-dated) level of our understanding of the particle acceleration at the Sun and SEP propagation in the interplanetary magnetic field (IMF). The author apologizes if some results of numerous space researchers were given rather briefly, or were not mentioned at all. Below we concentrate on several unresolved problems in the study of solar cosmic rays, their sources, and related theoretical, observational, and methodological issues.