Propagation Of High Energy Particles Research Articles

Propagation of high-energy particles inside solid matter: cosmic-ray-induced spallation in iron meteorites

A model is presented to evaluate the variations with depth of high-energy particle fluxes as they propagate inside spherical solid bodies. This model can be used to calculate the production rates of spallogenic nuclides inside meteorites of various sizes and compositions. The exponential attenuation of the flux, the gradual energy loss due to the Coulombian drag and the production of secondary particles in the spallation reactions are all taken into account in a self consistent way. It is shown that, in the energy range considered (300 MeV to 30 GeV), the particle fluxes are fairly insensitive to the actual angular distribution of the emitted secondary particles, as long as the assumed distribution remains within realistic limits. The propagation equations resulting from these interactions are solved on a spherical mesh consisting in a set of lines of various directions inside the sphere. The computed neutron and proton fluxes are presented in the case of an iron sphere irradiated by galactic cosmic ray (GCR) protons: these results show the critical importance of secondary particles and especially neutrons as depth increases within the sphere. The fluxes are used to calculate the production rates of some cosmogenic nuclides inside iron meteorites. The use of such production rates to gain information on exposure geometry of these meteorites and on the history of the GCR fluxes is discussed through a comparison with experimental data for the iron meteorite Grant. It is shown that the distribution of the different estimated ages within a meteorite could be used to distinguish between a spectral variation and an intensity variation of the GCR flux.

Acceleration of cosmic rays by shock waves

Theoretical work on various processes by which shock waves accelerate cosmic rays is reviewed. The most efficient of these processes, Fermi acceleration, is singled out for special attention. A linear theory for this process is presented. The results found on the basis of nonlinear models of Fermi acceleration, which incorporate the modification of the structure caused by the accelerated particles, are reported. There is a discussion of various possibilities for explaining the generation of high-energy particles observed in interplanetary and interstellar space on the basis of a Fermi acceleration mechanism. The acceleration by shock waves from supernova explosions is discussed as a possible source of galactic cosmic rays. The most important unresolved questions in the theory of acceleration of charged particles by shock waves are pointed out.

On the generation of high-energy particles in solar flares

This paper discusses the relationship between some characteristics of microwave type IV radio bursts and solar cosmic ray protons of MeV energy. It is shown that the peak flux intensity of those bursts is almost linearly correlated with the MeV proton peak flux observed by satellites near the Earth and that protons and electrons would be accelerated simultaneously by a similar mechanism during the explosive phase of solar flares. Brief discussion is given on the propagation of solar cosmic rays in the solar envelope after ejection from the flare regions.

A note on the acceleration phase of high-energy particles in the solar flare on 7 July, 1966

The acceleration phase of solar cosmic rays and relativistic electrons is studied on the basis of the observational data available on the optical, radio, X-ray, and particle events associated with the solar flare that occurred on July 7, 1966. The generating process of hydromagnetic shock waves which excited the type-II radio burst detected at a frequency below about 100 MHz is also discussed. The results of the study suggest that no secondary acceleration process after the explosive phase can contribute much to the generation of high energy particles. The ejection of solar cosmic rays and relativistic electrons seems to be related to the expansion of the magnetic bulge which can trap accelerated electrons from the triggering region of solar flares.

The Occurrence of High-Energy Releases during Flares in Localized Areas of an Active Center and Time-Associated Changes in SPOT Umbrae

view Abstract Citations (2) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Occurrence of High-Energy Releases during Flares in Localized Areas of an Active Center and Time-Associated Changes in SPOT Umbrae McKenna-Lawlor, Susan M. P. Abstract Although many flares occurred in active center HAO-59Q during its fifth passage across the solar disk, 1959 July 7-21, it is shown that only two localized areas within this region were associated with the commencement of significant energy releases. The energy importance of individual optical brightenings has been gauged by the magnitude of time-associated single-frequency radio bursts. In certain cases, localized high-energy flaring appears to be followed by extensive low-energy flaring, and such events are here called "primary flares" and "secondary flares," respectively. The positions of persistent flare-sensitive regions, calcium plages, filaments, and spot umbrae in HAO-59Q have been compared with the daily magnetograms of this center of activity published by the Crimean Astrophysical Observatory for 1959 July 14-17 The flare-sensitive regions were located near filaments and adjacent to the two sides of the loci of zero longitudinal magnetic field strengths. The magnetograms closely reflect local daily changes in the sunspots; hence, any role played by flares of high energy in producing changes in the magnetic field cannot be deduced unambiguously from these records. It is shown that the parts of the chromosphere associated with high-energy flares were directly over areas of the photosphere which contained transient umbrae. Flares with high energy occurred in intervals within which such umbrae disappeared or diminished in area. A close association between localized, highenergy flaring and an underlying changing spot umbra may be a necessary condition for the generation of high-energy particles. Publication: The Astrophysical Journal Pub Date: January 1970 DOI: 10.1086/150289 Bibcode: 1970ApJ...159...51M full text sources ADS |

Development of Sudden Ionospheric Disturbances (SID) Associated with Solar Cosmic-Ray Flares

Solar cosmic-ray flares are always followed by intense sudden ionospheric disturbances (SID). By examining the developing process of SID's, some problems such as the characteristics of cosmic-ray flares and associated X-ray emissions and the generation of high-energy particles are investigated.The nature of cosmic-ray flares is closely related to some observed characteristics of solar cosmic-rays and the developing process of SID's.The emission process of solar flare X-rays and its relation to the acceleration of energetic particles are considered.

Cosmic ray phenomena during the November 1960 solar disturbances

A preliminary analysis of cosmic-ray neutron monitor intensity data during the November 1960 solar disturbances is presented. The first increase on November 12 is attributed to generation of particles on the sun, following a class 3+ flare. A second increase on November 12 is interpreted as the arrival at the earth of solar particles trapped in the gas cloud emitted by the sun in connection with a previous flare. It is shown that the arrival of a further cloud sweeps away the remaining solar particles. The increase on November 15 is attributed to a new generation of high-energy particles by another class 3+ flare that occurred on the same solar active region. The characteristics of the solar flare increases are shown to agree with the conclusions of McCracken and Palmeira regarding the propagation of solar particles in interplanetary space. Data from low latitude stations are used to investigate the Forbush decreases and their relation with other solar and terrestrial events.