Israel Cosmic Ray Center affiliated to Tel Aviv University, Technion, and Israel Space Agency operating the Emilio Segre Cosmic Ray Observatory and World Data Center for Cosmic Rays (transported from Sweden)
Report No 1/1998
Establishment of the Observatory and preliminary research results
The aims of this project for the first three years, starting in November 1997, are as follows:
· to establish the Israel Cosmic Ray Center, including a Cosmic Ray Observatory, based on a collaboration with the Italian Cosmic Ray Group, who graciously put at our disposal the neutron monitor previously utilized at their Antarctic Observatory,
· to establish a World Data Center for Cosmic Rays, based on an archive graciously put at our disposal by the Swedish Cosmic Ray Group,
· to enact a research program in Cosmic Ray Astrophysics and in Geophysics,
· in collaboration with other Cosmic Ray Observatories, to develop analytical methods of forecasting anomalous Cosmic Radiation events, representing changes in the Interplanetary and Near-Earth environment. Such events could possibly be harmful to space-probes, to earth orbiting equipment, to air-travel, to electromagnetic communications and perhaps even to living beings on Earth. Phenomena which might indicate such developments include, for example, large solar flares, the impacting of energetic particles and Forbush-decreases connected with large geomagnetic disturbances. The network of observatories providing such early-warning services will form the International Cosmic Ray Service.
1. ORGANIZATION AND EXPERIMENT
· The Israel Cosmic Ray Center has indeed been established, with affiliations to Tel Aviv University, to the Technion (Israel Institute of Technology) and to the Israel Space Agency (under the aegis of the Ministry of Science). The staff of the Israel Cosmic Ray Center is as follows: 1. Prof. L.I. DORMAN - principal investigator, head of the Center and Observatory; 2. Dr. L.A. PUSTIL¢NIK - researcher, 3. Dr. I.G. ZUKERMAN - researcher, and 4. Dr. A.G. ZUSMANOVICH researcher. The following necessary facilities were put at its disposal:
· The Mobile Cosmic Ray Neutron Monitor, supplied by the Italian group, as above mentioned, was prepared for reutilization, in collaboration with scientists of the Italian group in Rome, and transferred in June 1998 to the site selected for the Emilio Segre Observatory (33°18.3¢N, 35°47.2¢E, 2020 m above sea level, cut-off rigidity for vertical direction Rc=10.8 GV).
· Measurements of general cosmic ray intensity, of air pressure, and of the specific intensities for neutron multiplicities ³1, ³2, ³3, ³4, ³5, ³6, ³7 and ³8 were performed at sea level in the port of Haifa and for the Emilio Segre Observatory site, at the ski lifts both lower and upper stations. With these data, the cosmic ray barometric coefficients for Israel were determined, using information on primary cosmic ray variations as set by the Rome and other cosmic ray observatories neutron monitor data.
· The (Israel-Italy) Emilio Segre Cosmic Ray Observatory has been operational since June 1998 in a continuous (24 hours per day) mode.
· The results of measurements data taken at one minute intervals -- of cosmic ray neutron intensities at two separate sites, as well as similar one-minute data about the intensities relating to neutron multiplicities ³1, ³2, ³3, ³4, ³5, ³6, ³7 and ³8 all of this data has been computer-stored.. Similar one-minute data relating to air pressure, as well as temperature and humidity -- inside the Cosmic Ray Observatory have also been recorded.
· The archive of the World Data Center for Cosmic Rays was transferred from the MIGAL Research Center in Qiryat Shmona (where it had been stored since its arrival from Sweden) to the Cosmic Ray Centers temporary offices at Qatzrin and made available for research utilization.
The Cosmic Ray Center research activities have dealt with the following issues:
· THE DEVELOPMENT OF METHODS FOR THE PROTECTION OF
ELECTRONICS ON SPACE PROBES, BASED ON THE USE OF ONE-MINUTE DATA,
AS MEASURED AT THE EMILIO SEGRE COSMIC RAY OBSERVATORY AND AT
SEVERAL OTHER COSMIC RAY OBSERVATORIES IN THE WORLD.
The effects of galactic cosmic rays and solar flare energetic particles (FEP) on micro-electronics codes on spacecraft represent an important issue and have been dealt with in depth by many authors (see - and references therein). Especially dangerous are single event phenomena (SEP)  sometime even capable of destroying computer memories on earth, but obviously with a much larger probability, in spacecraft systems; according to ref. , during periods of large energetic particle fluxes, it is advisable to switch off some part of the electronics, to protect computer memories from these SEP. This requires early warning; can we provide it? In principle this can be obtained by monitoring high energy particles originating in the Sun. These particles arrive much earlier than the mainstream, constisting of middle energy particles, with a large flux, thereby endangering the electronics. The high energy particles flux, on the other hand, is very small and cannot be monitored with enough accuracy on the spacecraft itself. The monitoring has thus to be performed (in a continuous mode) by ground-based neutron monitors and muon telescopes, with minimal statistical errors (thus requiring large effective surfaces).
This type of Early Warning fits well with the capabilities of the planned International Cosmic Ray Service (ICRS) , to be organized in the near future around the Israel Cosmic Ray Center (ICRC) and its Emilio Segre Cosmic Ray Observatory (ESCRO) run jointly with the Italian group, with a world-wide network of cosmic ray observatories (the Project has been presented to UNESCO).
The implementation of the Early Warning system will be as follows. The ICRC will establish a special page in the Internet, later to be replaced by that of the ICRS. This page will present in real time 5-minute and/or 1-minute data, from the monitors of the Emilio Segre Cosmic Ray Observatory (ESCRO), together with data to be supplied by other observatories -- Rome, Moscow, Kiev, Apatity, Irkutsk, Novosibirsk, Alma Ata, Aragaz, Mexico, Haleakala, Chacaltaya, etc.. The data will be continuously processed, in real time, by the ICRC central computer in Qazrin.
Should the data from any one observatory display an increase in cosmic ray intensity by a factor of 3 or more, it will trigger a program ''Alert 1''. This will compare the increase with data from other observatories and with the situation in the next time period.
Should the integrated data indicate the beginning of a FEP event, it will launch a program ''Alert 2''. This will take into account the position and properties of the solar flare (should this information be available) and provide a preliminary description of the FEP event. Note that in order to calculate the energy spectrum of the FEP, the data will have to include the parameters of the FEPs source on the Sun, the propagation parameters through the corona and in interplanetary space. On the basis of this preliminary model, the program will provide a preliminary estimate of the expected radiation situation after 20-60 minutes.
Should the expected level of radiation represent a danger for electronic systems in spacecraft, a preliminary alert will be declared, thereby also triggering a program ''Alert 3''. This program will continue processing data, including that of the next period -- thus further improving the preliminary model and obtaining a final model of the FEP event. It will provide a more precise evaluation of the expected time profile of the FEP flux, as function of particle energy. It will also predict the expected radiation hazard for different types of spacecraft orbits and for spacecraft in the Heliosphere, as a function of the distance to the Sun and disseminate that information.
Should the expected radiation be higher than a certain bound, similar evaluations will be made for aircraft, as a function of altitude and cut-off rigidity, as well as for human beings and technology on the ground, the dependence on altitude in the case of high ground.
Programs Alert 1, 2 and 3, as well as the correlated procedure of computer evolving reconstruction of the profiles of FEP events, will be tested with data from large historical FEP events, as described in detail in -.
 J. Levinson et al., Appl. Phys. Lett, 63, 2952, (1993).
 J. Barak et al., IEEE Trans. Nucl. Sci., 43, 907, 979, (1996).
 A.J. Tylka et al., IEEE Trans. Nucl. Sci., 44, 2150, (1997).
 J. Barak et al., Annual Report, Israel Atomic Energy Commission, (1995).
 L.I. Dorman et al., Astrophys. and Space Sci., 208, 55, (1993).
 L.I. Dorman, Cosmic Ray Variations, Moscow, Gostehteorizdat, (1957); Washington DC, (1958).
 L.I. Dorman, Cosmic Ray Variations and Space Research, Moscow, Nauka, (1963).
 L.I. Dorman, Astrophysical and Geophysical Aspects of Cosmic Rays, in serie
''Progress in Elementary Particle and Cosmic Ray Physics'', Vol. 7, Amsterdam,
 L.I. Dorman, L.I. Miroshnichenko, Solar Cosmic Rays, Moscow, Fizmatgiz, (1968); NASA, (1976).
 L.I. Dorman, Cosmic Rays: Variations and Space Investigations, Amsterdam,
 L.I. Dorman, Cosmic Rays of Solar Origin, Moscow, VINITI, (1978).
 L.I. Dorman, D. Venkatesan, Space Sci. Rev., 64, 183-362, (1993).
· GAMMA RAYS AND NONLINEAR PROCESSES.
The first study of "Cosmic ray nonlinear processes in gamma-ray sources" was published by Dorman (1996). The theme was further developed, by considering two aspects, namely gamma ray generation (1) by local energetic particles and (2) by galactic cosmic rays.
In the first aspect, on the basis of data about the generation of solar flare energetic particles and their propagation in the Heliosphere, we calculated the interaction of these particles with matter in the interplanetary space and estimated the angular distribution and time variation of the generated gamma ray flux. For some simple diffusion models of solar flare energetic particle propagation, we were able to obtain an analytical approximation, describing the time evolution of the gamma ray flux angular distribution as well as that of the gamma ray spectrum. We applied the results obtained to an evaluation of the gamma-ray flux from the solar wind for some powerful historical events, thus determining the necessary sensitivity and angular resolution of the gamma ray telescope for the detection of these phenomena, considering their capacity of providing important information on the space-time distribution of the solar energetic particles and of solar wind matter, in the interplanetary space. We also estimated the expected gamma ray fluxes from the interaction of flare energetic particles with stellar winds, for different types of stars. The main conclusions of our investigations are as follows:
1) On the basis of the analytical solutions obtained, we established the possibility ofmonitoring the 3D solar cosmic ray propagation and the solar wind matter distribution, as well as the 3D-distribution of solar wind velocities in the inner Heliosphere -- in periods of large solar cosmic ray events basing our measurements on the observation of gamma rays generated by the interaction of solar flare energetic particles with solar wind matter.
2) In the case of stars, the observation of gamma rays produced by the interaction of stellar flare energetic particles with stellar wind matter, can give important information on the stellar flare cosmic ray spectrum and mode of energetic particle propagation, as well as on the stellar wind matter distribution.
In the second aspect, we used results obtained in our investigation of galactic cosmic rays the hysteresis phenomena in solar activity, a variability in cosmic ray modulation parameters during the solar cycle -- to calculate the evolution of the cosmic ray density distribution in the Heliosphere, during the solar cycle, as a function of particle energy. We also used the recent Ulysses data on the helio-latitude distribution of the solar winds speed and density, including its possible change during the solar cycle. We then calculated the expected time variation of the angular distribution and of the spectra of the gamma ray flux, as generated by the interaction of modulated galactic cosmic rays with solar wind matter. These calculations were done for gamma ray observation on the Earth as well as for observation from space probes at different distances from the Sun. Our results show what type of gamma ray telescope can be used to detect with good accuracy gamma rays generated by the interaction of galactic cosmic rays with solar wind matter; the investigation of this phenomenon can provide important additional information on the solar wind distribution and cosmic ray modulation during a solar cycle. We also evaluated the expected gamma ray flux generated by galactic cosmic ray interaction with stellar wind matter, taking into account a possible modulation, in different stellar types . The main results obtained are as follows:
1) We derived an equation describing the space-time distribution of the gamma ray emissivity caused by the interaction of galactic cosmic rays with solar and stellar wind matter, taking into account modulation and nonlinear processes.
2) The expected angular distribution and time variations of gamma ray fluxes were evaluated for a local observer and it was shown that these observations will give important information on galactic cosmic ray modulation and nonlinear processes in the Heliosphere as well as on the solar wind matter 3D space-time distribution.
3) We derived an equation (with its solution) for the expected time variations of the gamma ray flux and of the energy spectrum of the stellar wind, for a distant observer; these observations will provide important information on galactic cosmic ray modulation and on nonlinear processes in stellar winds, on stellar activity cycles and on the stellar wind matter distribution.
· RADIOCARBON COUPLING FUNCTIONS AND MODULATION,
ACCELERATION AND NONLINEAR PROCESSES IN THE PAST.
This problem has 2 parts. In the 1st part (general) we consider how cosmogenic nuclides (more than one hundred stable and unstable isotopes) are continuously generated by nuclear interactions of cosmic ray particles (primary protons and nuclei as well as secondary cosmic ray nuclear-active particles like neutrons, secondary protons, pions and others) with matter: 1) in space (interstellar gas and dust, molecular-gas clouds, solar and stellar winds), 2) on surfaces of bodies and inside bodies (meteorites, asteroids, planets and satellites without atmospheres, bodies of comets), 3) in atmospheres of planets and stars. Cosmogenic nuclides contain very important information on the history of cosmic rays as well as on the history of many astrophysical objects; the problem is how to extract this information. In this part we consider the general equations and their solutions, determining the space-time variability of cosmogenic nuclide production reactions and rates in various astrophysical environments (space, bodies, atmospheres) by the coupling functions method, previously developed in cosmic ray variability research. The main results of this part:
1. The production rate of cosmogenic nuclides in space (galactic disc and halo with galactic wind, solar and stellar winds, molecular-dust clouds, etc.) is determined from the spectrum and contents of primary cosmic ray particles, using the composition of background matter and from the integrated multiplicities of cosmogenic nuclides generated in nuclear interactions of cosmic ray particles with matter. As the depth of matter traversed by cosmic rays is much smaller than the mean-free-path for nuclear interactions, the development of meson-nuclear cascades and the generation of secondary nuclear-active particles will be negligible. The composition of cosmogenic nuclides in space and their time variability are determined from the variations in the production rates of cosmogenic nuclides (related to the variations of the cosmic ray spectrum, through the abovecoupling functions), from the parameters of nuclear decays and from the mechanism of element exchange. The solution obtained for the two-reservoir model of element exchange, for instance, can thus be used to estimate the expected production rate of cosmogenic nuclides in space, their composition and their possible time and space dependence.
2. In the production of cosmogenic nuclides inside astrophysical bodies without atmospheres (meteorites, asteroids, central bodies of comets, planets and planetary satellites with no atmospheres or with very thin ones, i.e. a depth much smaller than the mean-free-path for nuclear interactions) it is very important to take into account the nuclear-meson cascade of cosmic ray particles with generation of secondary nuclear-active particles. The composition of the cosmogenic nuclides inside these astrophysical bodies and their time variability are determined from the time-evolution of the production rate of cosmogenic nuclides (related through the above-mentioned coupling functions to the variability of the cosmic ray spectrum and to the actual trajectories of moving objects) and from the various decay parameters. The data on the composition of cosmogenic nuclides in meteorites and in moon samples can be used, together with the solutions of the equations for the production rates and for the evolving composition, to determine the history of cosmic rays as well as that of various astrophysical bodies, up to several billion years ago..
3. For the production of cosmogenic nuclides by galactic and local cosmic rays inside the atmospheres of stars and planets, and for their contents and time variations it is very important to take into account the cosmic ray nuclear-meson cascade in the atmosphere in terms of integrated multiplicities and coupling functions, vertical mixing of elements as well as global mixing, exchange of elements between reservoirs with different production rates of cosmogenic nuclides. Solutions of equations are obtained, which describe the evolution of production rate and composition of cosmogenic nuclides, taking into account possible local cosmic ray sources and cosmic ray cyclic modulations. On the basis of these solutions it is possible to solve the inverse problem and to determine the main properties of local supernova explosions and cosmic ray cyclic modulations in the past, from the data on cosmogenic nuclides with their different decay constants
In part 2 we considered in more detail the method of local and planetary cosmogenic nuclide coupling functions, specifically for the case of the Earth. We introduce and calculate the local and polar radiocarbon coupling functions for the Earth's atmosphere, taking into account a vertical mixing of elements. We then introduce and calculate the global coupling function, taking into account global element mixing and the influence of the geomagnetic field on the cosmic ray planetary distribution. For the contents of radiocarbon in the atmosphere and in dated samples there are very important exchange processes between several reservoirs on the Earth. As a first approximation, we consider a two-reservoir model, later replacing it by a five-reservoir element exchange model. Comparing with experimental data on radiocarbon composition, we estimate the exchange parameters. Using the methods we developed, we thus obtained solutions determining the time evolution of radiocarbon production rates and the composition of the Earth's atmosphere. We used data from atmospheric atomic bomb tests to evaluate cosmic ray time variations in the past, caused by changes of the geomagnetic field, by solar activity cycles, and by possible local supernova explosions. The main results of this part are as follows:
1. The method of polar and local radiocarbon coupling functions which we developed allowed us to relate the cosmic ray spectrum and the variation of its cut-off rigidity with changes in the radiocarbon production rate, taking into account vertical mixing of elements in the Earth's atmosphere. We derived analytical approximations of the polar and local radiocarbon coupling functions.
2. The introduction and calculation of global radiocarbon coupling functions allowed us to take into account the global mixing of elements in the Earth's atmosphere and to derive the correlation between time variations of the global radiocarbon production rates and changes in the cosmic ray primary spectrum and in the Earth's magnetic dipole moment.
3. Consideration of the 2-reservoir model of global element-exchange on Earth, taking into account data on atomic bomb atmospheric explosions, allowed us to determine the probabilities for the various element exchanges and to derive, on the basis of the radiocarbon contents in the dated samples, the global radiocarbon production rate in the atmosphere, as well as cosmic ray intensity variations in the past. Within the frame of this model, we determined the effect of different types of cosmic ray time variations on the radiocarbon content.
4. In the same approximation, the probabilities of element-exchange within the frame of the 5-reservoir model were estimated, yielding a steady-state solution and a set of calculated parameters for the nonstationary solution.
5. On the basis of the method of radiocarbon coupling functions, within the frame of global mixing and using the element-exchange model we considered, we analyzed the radiocarbon and 10Be datas impact on cosmic ray variations in the past, connected with long-term variations of the Earth's magnetic field, solar activity cycles, and possible supernova explosions not far from the Sun.
· THE PROBLEM OF GAMMA RAY AND COSMIC RAY GENERATION BY
PAST SUPERNOVA EXPLOSIONS AND YOUNG PULSARS.
We considered in detail the production of neutrons in the Earths atmosphere in the past, by gamma rays and by cosmic rays from supernova explosions and the ensuing young pulsars; the interaction of neutrons with atoms of nitrogen generates radiocarbon 14C with a decay time of 5730 years. The nuclear interactions of gamma rays and cosmic rays with atoms of the atmosphere generate, in addition, various other cosmogenic radionuclides. Using cosmogenic radionuclides coupling functions, taking into account vertical and global mixing and element-exchange processes on the Earth, on the basis of experimental data of radiocarbon content in annual rings of trees and on the content of some other cosmogenic radionuclides in dated samples, it became possible to estimate the gamma ray fluxes from supernovae explosions and from young pulsars in our Galaxy in the last few thousand years -- as well as cosmic ray fluxes from local supernovae explosions (up to about 100 pc from the Sun) in the last 150 thousand years. The main results are as follows:
1. Using radiocarbon coupling functions, taking into account mixing and exchange processes of elements on the Earth, it is possible to solve the inverse problem, namely to estimate gamma ray fluxes from young pulsars in our Galaxy, using experimental data relating to radiocarbon contents
2. This inverse problem can only be solved and exact information on diffusion coefficients and energetic characteristics can only be obtained for local supernovae, within a distance of a hundred pc from the Sun.
3. The total energy in cosmic rays estimated from the gamma ray effect for the supernova 1006 AD and from the cosmic ray effect for a local supernova (probably to be identified with SNR Loop 1) is about 1050 ergs.
4. For a more precise investigation of the gamma ray effect in radiocarbon, it will be necessary to determine the coupling function more accurately and to sufficiently reduce the statistical errors for radiocarbon measurements in dated samples; progress in this area will make it possible to obtain important information on the gamma ray effect for several hundred young pulsars in our Galaxy in the past, and on the cosmic ray effects for a number of local supernovae explosions.
· COSMIC RAY ANISOTROPIES AND NONLINEAR PROCESSES.
The data on cosmic ray convection-diffusion and drift anisotropy in the Heliosphere are very important for the stof the kinetic stream instability. Cosmic ray anisotropy is one of the main characteristics of galactic cosmic rays. We found that the observed cosmic ray anisotropy in the interplanetary space consists mainly of two parts, with different origins and a different dependence on particle rigidity. One part is produced by cosmic ray convection-diffusion processes, while the other originates in drift processes. Both parts are connected with cosmic ray gradients and with the cosmic rays propagation parameters in space. In what follows, we briefly review some statistical properties of the 3-dimensional, North-South and ecliptic cosmic ray anisotropies in the Heliosphere, and the determination from the cosmic ray anisotropy data of the transport parameters for cosmic ray propagation; also, from the distribution of the gradients of the cosmic ray density in interplanetary space, the determination of the separation of convection-diffusion and drift anisotropies and their properties, in terms of their dependence on rigidity, from a few GeV up to 330 GeV, evaluated on the basis of cosmic ray observations (for about 25 years) by ground neutron monitors and underground muon telescopes. The main results are as follows:
1. We were able to evaluate (statistically) the degree of IMF irregularity, as well as the cosmic ray transport parameters and density gradients, from the data about the cosmic ray anisotropy, basing our calculations on a convection-diffusion model of anisotropy formation, corrected for drift effects.
2. The investigation of the North-South cosmic ray anisotropy has yielded important information on the anisotropy near the heliospheres electrically-neutral sheet and related high-velocity solar wind streams, including the long-term variations related to the solar magneticc cycle and the annual change of the Earths heliolatitude.
3. The statistical investigation of the interrelation between amplitude and phase, including (as a phase distribution) the first harmonic of the cosmic ray anisotropy, makes it possibile, using the convection-diffusion model of cosmic ray anisotropy spatial formation and correcting for drift effects, to estimate the distribution of cosmic ray density radial and latitudinal gradients as a function of solar magnetic polarity.
4. Using the annual change of the Earth's heliolatitude, with the IMF and cosmic ray many-year data from neutron monitors and underground muon telescopes, we were able to separate the convection-diffusion and drift anisotropies for the south, equatorial and north zones of the Earth position (relative to the helioequator plane) and investigate their properties separately; we found that the relative role of the cosmic ray drift anisotropy increases with increasing particle rigidity, from 8 % at 16 GeV to about 32 % at 330 GeV.
5. Within interplanetary space, there exist two local latitudinal cosmic ray gradients. The first is related to the position of the heliospheric neutral sheet, being directed on the average either away from the sheet, or toward the sheet from both sides, with a dependence on the solar magnetic polarity; the second gradient is connected with the latitudinal distribution of the solar activity, the solar wind speed and IMF parameters. Over many years it averages with opposite signs in the south and north zones of the Earths position, relative to the helio-equatorial plane, decreasing proportionally to the inverse of particle rigidity.
· COSMIC RAYS - SOLAR ACTIVITY HYSTERESIS PHENOMENA AND
NONLINEAR PROCESSES IN THE HELIOSPHERE.
Cosmic rays-solar activity hysteresis phenomena are caused by nonlinear processes in the outer Heliosphere. Our main results are as follows:
1. The cosmic ray-solar activity hysteresis phenomenon has been investigated, on the basis of the cosmic ray neutron monitor data, as well as on solar activity data for 4 solar cycles. The results indicate that the high rigidity cosmic ray particles only determine the effective dimensions of the modulation region in the Heliosphere (depending on particle rigidity), but not the distance from the Sun to the terminal shock wave. This effective dimension of the modulation region decreases as the cosmic ray rigidity increases. The high rigidity cosmic ray particles do not reflect the situation outside of the modulation region, up to the terminal shock wave. The global time variation contains important information on the cosmic ray diffusion coefficient distribution in the inner Heliosphere and its connection with the solar activity.
2. The hysteresis phenomenon was investigated, for several different sets of assumptions regarding the cosmic ray diffusion coefficients relationship with the solar activity and the coefficients distribution in the Heliosphere. This was done on the basis of low rigidity cosmic ray intensity data, as obtained for the last several solar cycles from ground-based neutron monitors,
Comparing the expected cosmic ray - solar activity hysteresis with the actually observed one, we were able to determine in the first approximation the average Dependence on particle rigidity, given the solar cycle dimension of the Heliosphere and cosmic ray propagation parameters, as well as the expected cosmic ray intensity out of the Heliosphere. The results, obtained separately for odd and even solar cycles, have been compared and discussed in the frame of the cosmic ray convection-diffusion models propagation in the Heliosphere, correcting for drift effects.
3. On the basis of this investigation of cosmic ray-solar activity hysteresis phenomena, using data from the Climax and Huancayo/Haleakala neutron monitors for 1953-1996, as well as solar activity data, we have approximately determined the expected change in the cosmic ray modulation regions dimensions and in the position of the terminal shock wave, during the solar cycle.
4. Still on the basis of the investigation of the cosmic ray - solar activity hysteresis phenomenon, with the dependence on cosmic ray rigidity for the last few solar cycles, we have also determined the main parameters of the cosmic ray intensity modulation in the Heliosphere, with the dependence on particle rigidity and its connection with solar activity. We have then used solar activity data for several hundred years, to obtain information on the expected long-term time variations of cosmic ray intensity in the past (from 1750) for high-rigidity and middle-rigidity particles.
· SOLAR NEUTRON PROPAGATION AND REFRACTION EFFECT.
This problem, which is important for the investigation of particle acceleration and nuclear interaction processes, as well as for nonlinear processes on the Sun, was considered in detail, with the following main results:
1. The published experimental data on the largest solar neutron event give the amplitudes of increase, relative to galactic cosmic rays. To obtain absolute values of solar neutron increases, we recalculate these data, taking into account the type of detector used, as well as the change of galactic cosmic ray intensity as a function of altitude and cut-off rigidity. Under the assumption of straight-ahead transport through the atmosphere, the attenuation length of solar neutrons reduces from the unreasonably large value of 208 g/cm2 (as obtained by Shea et al., 1991; Debrunner et al., 1993) to 149 g/cm2. This value still clashes with the data on neutron cross-sections (Shibata, 1994). If we take into account the refraction effect as assumed by Smart et al. (1995), the attenuation length reduces to the unreasonably small value of 72 g/cm2. Our numerical simulation and analytical approximation for the problem of solar neutron scattering and attenuation in the Earths atmosphere for different initial zenith angles and different observation levels (Dorman et al., 1997; Dorman & Valdes-Galicia, 1997) does surmount this contradiction, showing that the refraction effect in solar neutron propagation exists but is not constant; it increases significantly with increasing initial zenith angle.
2. We obtained results of a simulation of small angle neutron multi-scattering with attenuation for different initial zenithangles and different atmospheric depths. These calculations were stimulated by results obtained by Dorman et al. (1997), on the solar neutron event of 24 May 1990.
3. For vertical arrival, our results for solar neutron fluxes are in good agreement with the calculations of Shibata (1994).
4. Shibata (1994) concluded that the expected solar neutron flux and angular distribution at depth h for an inclined arrival of neutrons at zenith angle will be the same as for a vertical arrival - for an equivalent depth . Our results show that this conclusion is not correct: the zenith angle distribution is symmetrical only for a vertical arrival of solar neutrons, whereas, for inclined arrival, it becomes asymmetrical and this asymmetry increases with increasing and observation depth h.
5. According to our results on the effective zenith angle , the refraction effect of solar neutrons, as suggested by Smart et al. (1995), does exist, but is not constant; its value increases with increasing . The value of decreases with increasing h; it is in agreement with the qualitative estimate of Smart et al.(1995).
· SOLAR COSMIC RAY ACCELERATION IN SOLAR FLARES AND THE
ORIGIN OF SOLAR FLARES
We have shown that a turbulent-current sheet of flares does not possess a steady state and will convert into a random mixture of turbulent and normal domains, as a result of different plasma instabilities (tearing-modes, pinch-like modes, overheating modes, etc). We describe this system as an inter-percolating random network of resistors and show that this approach is very effective, providing an explanation of the origin of flares as a phase transition - and correctly predicting the power spectrum of the flares spike distribution and the power spectrum of the accelerated particles.
· COSMIC RAY ORIGIN IN ACCRETED OBJECTS (GALACTIC BINARY
ACCRETION SYSTEM AND EXTRAGALACTIC OBJECTS OF BL LAC TYPE).
Cosmic ray acceleration in accreted objects is the result of the non-thermal mode of accretion. We have analyzed the relative stability of the standard accretion models, taking into account magnetic field generation and some instability in accreted plasma. We showed that in all standard accretion models, specific pinch-like jet structures have to be formed above the central object. We have proposed models in which the originating object is represented by a bulk of accelerated particles in pinch-like structures, undergoing instabilities and tearing. We have used this approach to explain the non-thermal activity of accreted objects, such as galactic binaries or BL Lac objects.
3. PARTICIPATION IN
CONFERENCES, SYMPOSIUMS AND SEMINARS
We presented reports at the Annual Meeting of the Israel Physical Society at the Weizmann Institute of Science, at the First Israel Conference on Plasma Physics, held at Tel Aviv University, at the 7-th International Conference on Plasma Astrophysics (Lindau, Germany), at the International School of High Energy Astrophysics (Erice, Sicily), at the 9th International Solar Wind Conference (Smithsonian Astrophysical Center, USA) and at the Cosmic Ray Symposium (University of New Hempshire, USA), the Moscow Cosmic Ray Conference and the Conference on the BL Lac Phenomenon, 22-26 June, 1998 in Turku., Finland. We also gave several reports at the Astrophysical seminar of the Technion Physics Department, at the Ben-Gurion University Physics Department seminar, at the Moscow Joint Astrophysical Seminar, at the 3rd Rome University Physics Department seminar, a report on gamma ray generation by cosmic rays in solar and stellar winds at the seminar of the University of Chicago and a report on cosmic ray variations and space-dangerous phenomena at the Space Environmental Center in Boulder (USA).
Our research activity is reflected in 45 papers and reports.
4. SCIENTIFIC PUBLICATIONS
OF THE ISRAEL COSMIC RAY CENTER DURING 1997 - 1998
1. Pustilnik L., 1997. Unsteady State of the Turbulent Current Sheet of a Flare. Astrophysics and Space Science, v. 252, Issue 1/2, p. 325-33
2. Ahluwalia H.S. & Dorman L.I., 1997. Transverse Cosmic Ray Gradients in the Heliosphere and the Solar Diurnal Anisotropy. J. Geophys. Res., 102A, pp 17433-17443.
3. Dorman L.I., Dorman I.V., and J.F. Valdes-Galicia, 1997. Simulation of solar neutron scattering and attenuation in the Earths atmosphere for different initial zenith angles. Proc. of 25- th Intern. Cosmic Ray Conference, Durban (South Africa), Vol. 1, pp 25-28.
4. Dorman L.I. & J.F. Valdes-Galicia, 1997. Analytical approximation to solar neutron scattering and attenuation in the Earths atmosphere. Proc. of 25- th Intern. Cosmic Ray Conference, Durban (South Africa), Vol. 1, pp. 29-32.
5. Dorman L.I., J.F. Valdes-Galicia, and M. Rodriguez, 1997. The event of 24 May 1990 and the problem of solar neutron propagation through the Earths atmosphere: does the refraction effect exist?. Proc. of 25- th Intern. Cosmic Ray Conference, Durban (South Africa), Vol. 1, pp. 33-36.
6. Dorman L.I., Iucci N. and Villoresi G., 1997. Auto-model solution for nonstationary problem described the cosmic ray preincrease effect and Forbush-decrease. Proc. of 25- th Intern. Cosmic Ray Conference, Durban (South Africa), Vol. 1, pp. 413-416.
7. Dorman L.I., Villoresi G, Dorman I.V., Iucci N. and Parisi M., 1997. High rigidity CR-SA hysteresis phenomenon and dimension of modulation region in the Heliosphere in dependence of particle rigidity. Proc. of 25- th Intern. Cosmic Ray Conference, Durban (South Africa), Vol. 2, pp. 69-72.
8. Dorman L.I., Villoresi G, Dorman I.V., Iucci N. and Parisi M., 1997. Low rigidity CR-SA hysteresis phenomenon and average dimension of the modulation region and Heliosphere. Proc. of 25- th Intern. Cosmic Ray Conference, Durban (South Africa), Vol. 2, pp 73-76.
9. Ahluwalia H.S. & Dorman L.I., 1997. Asymmetric cosmic ray transverse gradients at high rigidities. Proc. of 25- th Intern. Cosmic Ray Conference, Durban (South Africa), Vol. 2, pp 101-104.
10. Ahluwalia H.S. & Dorman L.I., 1997. Computation of transverse cosmic ray particle density gradients. Proc. of 25- th Intern. Cosmic Ray Conference, Durban (South Africa), Vol. 2, pp. 105-108.
11. Valdes-Galicia J.F. & Dorman L.I., 1997. 27-day cosmic ray variation and its relation to the interplanetary neutral current sheet tilt. Proc. of 25- th Intern. Cosmic Ray Conference, Durban (South Africa), Vol. 2, pp. 121-124.
12. Villoresi G., Iucci N., Tyasto M.I., Dorman L.I., Re F., Signoretti F., Zangrilli F., Cecchini S., Parisi M., Signorini C., Danilova O.A. and Ptitsyna N.G., 1997. Latitude survey of cosmic ray nucleonic component (Italy-Antarctic-Italy, 1996-1997). Proc. of 25- th Intern. Cosmic Ray Conference, Durban (South Africa), Vol. 2, pp. 421-424.
13. Dorman L.I., Valdes-Galicia J.F. and Rodriquez M., 1997. Multi-station comparative study of the nucleonic barometric coefficient dependence with altitude, cutoff rigidity and level of solar activity. Proc. of 25- th Intern. Cosmic Ray Conference, Durban (South Africa), Vol. 2, pp. 457-460.
14. Dorman L.I., Villoresi G, Dorman I.V., Iucci N. and Parisi M., 1997. Solar-cycle changes of cosmic ray propagation parameters and heliospheric terminal shock wave. Proc. of 25- th Intern. Cosmic Ray Conference, Durban (South Africa), Vol. 7, pp. 341-344.
15. Dorman L.I., Villoresi G, Dorman I.V., Iucci N. and Parisi M., 1997. On the expected CR intensity global modulation in the Heliosphere in the last several hundred years. Proc. of 25- th Intern. Cosmic Ray Conference, Durban, Vol. 7, pp. 345-348.
16. Dorman L.I., Dorman I.V., Villoresi G, Iucci N. and Parisi M., 1997. Expected time-variations of neutron monitor counting rate caused by CR particle energy change in the periods of thunderstorms. Proc. of 25- th Intern. Cosmic Ray Conference, Durban (South Africa), Vol. 7, pp. 349-352.
17. Dorman Lev I., 1997.Angle distribution and time variation of gamma ray flux from solar and stellar winds, 1. Gby flare energetic particles. Proc. of the Fourth Compton Symposium, ed. C.D. Dermer, M.S.Strickman, and J.D. Kurfess, AIP Conference Proceedings 410, Williamsburg, VA, Part 2, 1178-1182.
18. Dorman Lev I., 1997.Angle distribution and time variation of gamma ray flux from solar and stellar winds, 2. Generation by galactic cosmic rays.Proc. of the Fourth Compton Symposium, ed. C.D. Dermer, M.S.Strickman, and J.D. Kurfess, AIP Conference Proceedings 410, Williamsburg, VA, Part 2, 1183-1187.
19. Dorman Lev I., 1997.Gamma rays and cosmic rays from supernova explosions and young pulsars in the past.Proc. of the Fourth Compton Symposium, ed. C.D. Dermer, M.S.Strickman, and J.D. Kurfess, AIP Conference Proceedings 410, Williamsburg, VA, Part 2, 1172-1177.
20. Dorman Lev I., 1998. Cosmic rays and cosmogenic nuclides, 1. In space, inside bodies, in atmospheres. In Towards the Millennium in Astrophysics, ed. M.M. Shapiro and J.P. Wefel, World Sci. Publ. Co., Singapore (accepted for publication after referee report).
21. Dorman Lev I., 1998. Cosmic rays and cosmogenic nuclides, 2. Radiocarbon method and elements global mixing and exchange on the Earth. In Towards the Millennium in Astrophysics, ed. M.M. Shapiro and J.P. Wefel, World Sci. Publ. Co., Singapore (accepted for publication after referee report).
22. Dorman L.I., Valdes-Galicia J.F. and Dorman I.V., 1998. Simulation of solar neutron scattering and attenuation in the Earths atmosphere for different initial zenith angles. J. Geophys. Res. (submitted for publication).
23. Dorman L.I. & J.F. Valdes-Galicia, 1998. Analytical approximation to solar neutron scattering and attenuation in the Earths atmosphere. J. Geophys. Res. (submitted for publication).
24. Valdes-Galicia J.F., Dorman L.I. and M. Rodriquez, 1998. The event of 24 May 1990 and the problem of solar neutron propagation through the Earths atmosphere. J. Geophys. Res. (submitted for publication).
25. G. Villoresi, L.I. Dorman, N. Iucci, N.G. Ptitsyna, M. I. Tyasto. 1998. Natural and man-made low-frequency magnetic fields as a health hazard, UFN (Uspekhi Physicheskikh Nauk), 168, No. 7, pp. 767-791.
26. L.Dorman and V. Shogenov, 1998. Additional charged particle acceleration in space plasma with two types of scatterers, Astrophysics and Space Sci. (submitted for publication).
27. Lev I. Dorman, 1998. Cosmic ray nonlinear processes in space plasma: applications to the dynamic Heliosphere, Astrophysics and Space Sci. (submitted for publication).
28. Lev Dorman, 1998. Interaction of flare energetic particles with sollar and stellar wind plasma: expected space-time distribution of gamma ray emissivity, Astrophysics and Space Sci. (submitted for publication).
29. Lev Dorman, 1998. Angle distribution and time
variations of gamma ray fluxes generated by galactic cosmic rays
in solar and stellar winds, Astrophysics and Space Sci. (submitted
30. Lev Dorman & Vjacheslav Shogenov, 1998. Additional Charged Particle Acceleration in Space Plasma With Two Types of Scatterers: Applications to Some Astrophysical Objects. Meeting of Israel Physics Soc., Weizmann Institute of Science.
31. Dorman Lev, 1998. On the Prediction of Great Flare Energetic Particle Events to Save Electronics on Spacecrafts. Meeting of Israel Physics Soc., Weizmann Institute of Science.
32. Lev Dorman & Vjacheslav Shogenov, 1998. Cosmic Ray Propagation in Space Plasma With Two Types of Scatterers. Meeting of Israel Physics Soc., Weizmann Institute of Science.
33. Dorman L.I., 1998. Cosmic Ray Nonlinear Processes in the Outer Heliosphere and ExpectedProperties of Solar Wind and Cosmic Ray Modulation, Proc. of 9th Intern. Solar Wind Conf. (submitted for publication).
34. Dorman L.I., 1998. Time Variations of Gamma-Ray Emissivity Distribution Caused by Galactic Cosmic Ray Interactions with Solar Wind Matter , Proc. of 9th Intern. Solar Wind Conf. (submitted for publication).
35. Dorman L.I., 1998. Expected Gamma-Ray Fluxes from Solar Wind in Periods of Great Solar Energetic Particle Events, Proc. of 9th Intern. Solar Wind Conf. (submitted for publication).
36. Dorman L.I. and V.Kh. Shogenov, 1998. Additional Particle Acceleration in the Heliosphere Caused by Interactions with Scatterers Moving with Different Speeds, Proc. of 9th Intern. Solar Wind Conf. (submitted for publication).
37. Dorman L.I., G. Villoresi, I.V. Dorman, N. Iucci, and M. Parisi, 1998. Long-Term Cosmic Ray/Solar Activity Hysteresis Phenomenon and Properties of Solar Wind for the Last 200 Years, Proc. of 9th Intern. Solar Wind Conf. (submitted for publication).
38. Dorman Lev I., 1999. Cosmic ray anisotropies in space. In High Energy Astrophysics, ed. M.M. Shapiro and J.P. Wefel, Word Sci. Publ. Co., Singapore (in press).
39. Dorman Lev I., 1999. Interaction of flare energetic particles with solar and stellar wind plasma: expected space-time distribution of gamma-ray emissivity. Izvestia of Russian Acad. of Sci., Ser. of Physics (in press).
40. L. Dorman and V. Shogenov, 1999. Additional charged particle acceleration in space plasma with two types of scatterers. Izvestia of Russian Acad. of Sci., Ser. of Physics (in press).
41. Pustilnik L., 1997. Stability of Accretion Models in Astrophysics and Space Science, v. 252, Issue 1/2, p. 353-362.
42. Ikhsanov N., Pustilnik L., On the magnetic field configuration in the central cores of BL Lac objects in BL Lac Phenomenon, a conference held 22-26 June, 1998 in Turku, Finland.
43. Pustilnik L. On Stability of Accretion Models and "Hidden" Assumptions in Proceedings of the JENAM97 (Joint European and National Astronomical Meeting, 2-5.7.1997).
44. Pustilnik L.. Current Percolation in the Turbulent Current Sheet of Flare: Flare as a Threshold of Percolation, Precursors, Universal Amplitude-Frequency Spectrum in Proceedings of the JENAM97 (Joint European and National Astronomical Meeting, 2-5.7.1997).
45. Pustilnik L. Resonance Properties of the Coronal Magnetic Structure and Diagnostic of Pre-flare Evolution in Proceedings of the JENAM97 (Joint European and National Astronomical Meeting, 2-5.7.1997).
The staff of Israel Cosmic Ray Center thanks very much Prof. Yuval Ne¢eman for the constant attention and a great help in foundation of the Center and Emilio Segre Cosmic Ray Observatory; without this support our Project could not be successful. Cordial thanks to our Italian colleagues Prof. Nunzio Iucci and Dr. Giorgio Villoresi, to Director of Israel Space Agency Dr. Abi Hareven, Head of Import Department of TAU Avi Gurevich, to Shoshana Shalom, Matilda Elron, and Ronit Nevo for a great help in solving a lot of difficult problems connected with preparing and transportation of cosmic ray detector from Italy to Israel, and with organization and operating of Emilio Segre Cosmic Ray Observatory. On the early stage of our Project we had important attention and help from the former Minister of Science Dr. Beni Begin, head of Department of the Ministry of Science Frida Soffer, Prof. of Ben Gurion University David Eichler, former heads of Physical Department of Technion Prof. Gioro Shaviv and Prof. Moshe Moshe, Prof. Arnon Dar, Prof. Lev Pitaevskii, Prof. Aria Laor, Dr. Eretz Etzion, Major of Qazrin Sami Bar-Lev, Director of Golan Development Company Uri Meir, and Director-General of MIGAL Jacob Arzi.
Prof. Lev I. DORMAN, Technion, Israel Institute of Technology
Head of Israel Cosmic Ray Center and of Emilio Segre Cosmic Ray Observatory (affiliated to Tel Aviv University, supported in part by Israel Space Agency)
January 17, 1999