Propagation Of Protons Research Articles

Magnetic horizons of UHECR sources and the GZK feature

We study the effect of random extra-galactic magnetic fields on the propagation of protons of energy larger than 1019 eV. We show that for reasonable field values (in the 100 nG range) the transition between diffusive and ballistic regimes occurs in the same energy range as the GZK cutoff (a few 1019 eV). The usual interpretation of the flux reduction above the GZK energy in terms of a sudden reduction of the visible horizon is modified. Moreover, since the size of the diffusion sphere of a continuous source of cosmic rays is of the order of 10 Mpc, the local structure of the Universe and, therefore, of potential local astrophysical sources plays a dominant role in the expected spectrum. Under reasonable assumptions on the sources configurations the expected GZK cutoff is reduced.

Gelation of Octadecyltrimethoxysilane at the Air/Water Interface: Effect of Perfluorotetradecanoic Acid and Divalent Cadmium Ions

The effect of an acidic surfactant, perfluorotetradecanoic acid (PFTDA), on the gelation of octadecyltrimethoxysilane (ODTMS) monolayers at the air/water interface was investigated using a Langmuir film balance, attenuated total reflection (ATR) infrared spectroscopy, and atomic force microscopy (AFM). The gelation of ODTMS was greatly accelerated by adding only 2 mol % PFTDA into the monolayer; in this case, the hydrolysis of ODTMS was completed within a few minutes, whereas otherwise it took 18 h. ATR-IR spectroscopy clearly demonstrated that the gelation of a 49:1 ODTMS/PFTDA monolayer proceeded on a pure water subphase mainly via hydrolysis followed by condensation. In the presence of PFTDA, the local acidity at specific sites is presumed to be very high, catalyzing the hydrolysis of ODTMS. The extremely fast rate is attributed not only to the lateral diffusion of PFTDA in the mixed monolayer but also to proton propagation where the proton(s) involved in the initial hydrolysis are transposed rapidly to the nearby methoxy groups for subsequent hydrolysis. The catalytic activity of PFTDA can be neutralized, however, simply by the addition of multivalent metallic ions such as Cd2+ to form saltlike complexes with PFTDA; the rate of 2-D sol-gel processes can thus be easily regulated by a minute amount of PFTDA and/or Cd2+ added into the reaction system.

Propagation of ultra high energy cosmic rays

All particles of energy approaching 10 20 eV interact inelastically in the microwave background and other astrophysical photon fields and lose energy. We describe briefly the energy loss processes and show the consequences of proton propagation in extragalactic space. We also discuss the influence of astrophysical magnetic fields on the propagation. To cite this article: T. Stanev, C. R. Physique 5 (2004).

Propagation of ultrahigh energy protons in regular extragalactic magnetic fields

We study the proton flux expected from sources of ultra high energy cosmic rays (UHECR) in the presence of regular extragalactic magnetic fields. It is assumed that a local source of ultra-high energy protons and the magnetic field are all in a wall of matter concentration with dimensions characteristic of the supergalactic plane. For a single source, the observed proton flux and the local cosmic ray energy spectrum depend strongly on the strength of the field, the position of the observer, and the orientation of the field relative to the observer's line of sight. Regular fields also affect protons emitted by sources outside the local magnetic fields structure. We discuss the possibility that such effects could contribute to an explanation of the excess of UHECR above $5.10^{19}$ eV, and the possibility that sources of such particles may be missed if such magnetic fields are not taken into account.

Propagation of charged particles from the Galactic Center

Recent analysis of the anisotropy of cosmic rays at 1018 eV (the AGASA and SUGAR data) show significant excesses from regions close to the Galactic Centre and Cygnus. Our aim is to check whether such anisotropies can be caused by a single source of charged particles. We investigate propagation of protons in two models of the Galactic regular magnetic field (with the irregular component included) assuming that the particles are injected by a short lived discrete source lying in the direction of the Galactic Centre. We show that apart from a direct (prompt) image of the source, the regular magnetic field may cause indirect (delayed) images at quite large angular distances from the actual source direction. The observed image is strongly dependent on the time elapsed after ejection of particles and it is also very sensitive to their energies. For the most favourable conditions for particle acceleration by a young pulsar the predicted fluxes are two to four order of magnitudes higher than that observed. The particular numbers depend strongly on the Galactic magnetic field model adopted but it appears that a single pulsar in the Galactic Centre could be responsible for the observed excess.

The Role of Small Intraprotein Cavities in the Catalytic Cycle of Bacteriorhodopsin

The last phase of the proton transfer cycle of bacteriorhodopsin calls for a passage of a proton from D38 to D96. This reaction utilizes a narrow shaft ∼10-Å long that connects the two carboxylates that cross through a very hydrophobic domain. As the shaft is too narrow to be permanently hydrated, there are two alternatives for the proton propagation into the channel. The proton may propagate through the shaft without solvation at the expense of a high electrostatic barrier; alternatively, the shaft will expand to accommodate some water molecules, thus lowering the Born energy for the insertion of the charge into the protein (B. Schätzler, N. A. Dencher, J. Tittor, D. Oesterhelt, S. Yaniv-Checover, E. Nachliel, and G. Gutman, 2003, Biophys. J. 84:671–686). A comparative study of nine published crystal-structures of bacteriorhodopsin identified, next to the shaft, microcavities in the protein whose position and surrounding atoms are common to the reported structures. Some of the cavities either shrink or expand during the photocycle. It is argued that the plasticity of the cavities provides a working space needed for the transient solvation of the shaft, thus reducing the activation energy necessary for the solvation of the shaft. This suggestion is corroborated by the recent observations of Klink et al. (B. U. Klink, R. Winter, M. Engelhard, and I. Chizhov, 2002, Biophys. J. 83:3490–3498) that the late phases of the photocycle ( τ ≥ 1 ms) are strongly inhibited by external pressure.

TeV γ-rays and cosmic rays from the nucleus of M87, a mis-aligned BL Lac object

The unresolved nuclear region of M87 emits strong non-thermal emission from radio to X-rays. Assuming this emission to originate in the pc scale jet aligned at θ∼30° to the line of sight, we interpret this emission in the context of the synchrotron proton blazar model. We find the observed nuclear jet emission to be consistent with M87 being a mis-aligned BL Lac object and predict γ-ray emission extending up to at least 100 GeV at a level easily detectable by GLAST and MAGIC, and possibly by VERITAS depending on whether it is high-frequency or low-frequency peaked. Predicted neutrino emission is below the sensitivity of existing and planned neutrino telescopes. Ultra-high-energy neutrons produced in pion photoproduction interactions decay into protons after escaping from the host galaxy. Because energetic protons are deflected by the intergalactic magnetic field, the protons from the decay of neutrons emitted in all directions, including along the jet axis where the Doppler factor and hence emitted neutron energies are higher, can contribute to the observed ultra-high-energy cosmic rays. We consider the propagation of these cosmic ray protons to Earth and conclude that M87 could account for the observed flux if the extragalactic magnetic field topology were favourable.

Gauging of the PhoE Channel by a Single Freely Diffusing Proton

In the present study we combined a continuum approximation with a detailed mapping of the electrostatic potential inside an ionic channel to define the most probable trajectory for proton propagation through the channel (propagation along a structure-supported trajectory (PSST)). The conversion of the three-dimensional diffusion space into propagation along a one-dimensional pathway permits reconstruction of an ion motion by a short calculation (a few seconds on a state-of-the-art workstation) rather than a laborious, time-consuming random walk simulations. The experimental system selected for testing the accuracy of this concept was the reversible dissociation of a proton from a single pyranine molecule (8-hydroxypyrene-1,2,3-trisulfonate) bound by electrostatic forces inside the PhoE ionic channel of the Escherichia coli outer membrane. The crystal structure coordinates were used for calculation of the intra-cavity electrostatic potential, and the reconstruction of the observed fluorescence decay curve was carried out using the dielectric constant of the intra-cavity space as an adjustable parameter. The fitting of past experimental observations (Shimoni, E., Y. Tsfadia, E. Nachliel, and M. Gutman. 1993. Biophys. J. 64:472–479) was carried out by a modified version of the Agmon geminate recombination program (Krissinel, E. B., and N. Agmon. 1996. J. Comp. Chem. 17:1085–1098), where the gradient of the electrostatic potential and the entropic terms were calculated by the PSST program. The best-fitted reconstruction of the observed dynamics was attained when the water in the cavity was assigned ϵ ≤ 55, corroborating the theoretical estimation of Sansom (Breed, J. R., I. D. Kerr, and M. S. P. Sansom. 1996. Biophys. J. 70:1643–1661). The dielectric constant calculated for reversed micelles of comparable size (Cohen, B., D. Huppert, K. M. Solntsev, Y. Tsfadia, E. Nachliel, and M. Gutman. 2002. JACS. 124:7539–7547) allows us to set a margin of ϵ = 50 ± 5.

Images of very high energy cosmic ray sources in the Galaxy: I. A source towards the galactic centre

Recent analyses of the anisotropy of cosmic rays at 1018 eV (the AGASA and SUGAR data) show significant excesses from regions close to the galactic centre and Cygnus. Our aim is to check whether such anisotropies can be caused by single sources of charged particles. We investigate propagation of protons in two models of the galactic regular magnetic field (with the irregular component included) assuming that the particles are injected by a short-lived discrete source lying in the direction of the galactic centre. We show that apart from a prompt image of the source, the regular magnetic field may cause delayed images at quite large angular distances from the actual source direction. The image is strongly dependent on the time elapsed after ejection of particles and it is also very sensitive to their energy. For the most favourable conditions for particle acceleration by a young pulsar, the predicted fluxes are two to four orders of magnitude higher than those observed. The particular numbers strongly depend on the galactic magnetic field model adopted but it seems that a single pulsar in the galactic centre could be responsible for the observed excess.

Ultra high energy cosmic rays: clustering, GUT scale and neutrino masses

The clustering of ultra high energy (above 5 · 10 19 eV) cosmic rays (UHECR) suggests that they might be emitted by compact sources. We present a statistical analysis on the source density based on the multiplicities. The propagation of UHECR protons is studied in detail. The UHECR spectrum is consistent with the decay of GUT scale particles and/or with the Z-burst. The predicted GUT mass is m x = 10 b GeV, where b = 14.6 −1.7 +1.6. Our neutrino mass prediction depends on the origin of the power part of the spectrum: m ν = 2.75 −0.97 +1.28 eV for halo and 0.26 −0.14 +0.20 eV for extragalactic (EG) origin.

Ultra high energy cosmic rays and magnetic fields

We follow the propagation of ultra high energy protons in the presence of random and regular magnetic fields and discuss some of the changes in the angular and energy distributions of these particles introduced by the scattering in the magnetic fields.

Propagation of Ultra-High Energy Cosmic Rays from Sources in the Super-Galactic Plane

Abstract We have performed detailed numerical simulations on the propagation of UHE protons in the energy range $E = (10^{19.5} \hbox{--} 10^{22.0}) \,\mathrm{eV}$ in a relatively strong extragalactic magnetic field with a strength of $B = (10 \hbox{--} 100) \,\mathrm{nG}$ within about 40Mpc. In this case, the deflection angles of UHECRs become so large that the no counterparts problem can be simply solved. As for the source distribution, we assumed that it is proportional to the number distribution of galaxies within the Greisen–Zatsepin–Kuzmin sphere. We found many clusters, meaning small-scale anisotropy, in our simulations. It has also been shown that the observed energy spectrum is well reproduced in our models without any fine-tuned parameter. We used the correlation value in order to investigate statistically the similarity between the distribution of arrival directions of UHECRs and that of galaxies. We found that each correlation value for each parameter set begins to converge when the number of detected events becomes $O(10^3)$. Since the expected number counts by the experiment of the next generation, such as TA, HiRes, Auger, and EUSO, are thought to be on the order of $10^3$, we will be able to check in the very near future whether the source distribution of UHECRs is correlated with the Super-Galactic Plane or not. Compared with the AGASA data, a significant anisotropy on the arrival directions of UHECRs is found in the analyses of the first and second harmonics. This may originate from an incompleteness of the ORS database. This problem may also be solved if the source distribution is slightly changed. For example, this problem may be solved if we assume that UHECRs come from some galaxies, such as AGNs and radio galaxies.

Cosmic Ray and UV Radiation Models on the Ancient Martian Surface

The atmospheric evolution on Mars is influenced by nonthermal loss processes of heavy atmospheric constituents. Since Mars does not have an appreciable intrinsic magnetic field at present and a comparatively small gravitational acceleration, all known atmospheric loss processes can be active and several important constituents are lost to space. The escape rates of atmospheric constituents including water from Mars indicate that the red planet could have lost an atmosphere of at least 1 bar to space during the past 3.5 Gyr. We investigated with a theoretical model the atmospheric flux of cosmic-ray-induced particles on the martian surface by solving Boltzmann equations governing the propagation of protons, neutrons, muons, and pions in 7-mbar and 1-bar CO 2 atmospheres. We found that, at present, the thin atmosphere is not able to protect the surface of Mars from cosmic radiation and most of the incoming protons and neutrons impact the ground with energy fluxes of about 6000 and 1400 MeV cm −2 s −1, respectively. On the other hand, the much denser ancient atmosphere attenuated the radiation and only secondary particles, mainly muons, were able to reach the surface with energy fluxes of about 100 MeV cm −2 s −1, while the fluxes of protons and neutrons were negligible. We also evaluated the influence of an intrinsic magnetic field on the magnitude of the surface flux of charged cosmic particles and found no effect, even if one assumes an Earth-type magnetic field on ancient Mars, as suggested by recent Mars Global Surveyor magnetometer data. In addition we investigated the shielding of the martian surface from ultraviolet (UV) radiation by a dense early 1-bar CO 2 atmosphere including additional absorption effects of O 2 and O 3 and Rayleigh scattering. This atmosphere gradually becomes transparent to UV radiation above wavelengths of 220 nm.

Neutrinos from propagation of ultrahigh energy protons

We present a calculation of the production of neutrinos during propagation of ultra-high energy cosmic rays from their astrophysical sources to us. Photoproduction interactions are modeled with the event generator SOPHIA that represents very well the experimentally measured particle production cross sections at accelerator energies. We give the fluxes expected from different assumptions on cosmic ray source distributions, cosmic ray injection spectra, cosmological evolution of the sources and different cosmologies, and compare them to the Waxman-Bahcall limit on source neutrinos. We estimate rates for detection of neutrino induced showers in a km3 water detector. The ratio of the local high energy neutrino flux to the ultra-high energy cosmic ray flux is a crucial parameter in distinguishing between astrophysical and cosmological (top-down) scenarios of the ultra-high energy cosmic ray origin.

A novel approach to the mechanism of ionic conductivity below and at the ferroelastic phase transition in the zero-dimensional hydrogen-bonded crystals M3H(X04)2with (M = Rb or Cs; X = S or Se)

Abstract The temperature dependence of the proton conductivity in M3H(X04)2 (M = Rb or Cs; X = S or Se) is calculated for the low-conducting ferroelastic phase near the phase transition temperature, based on the phase transition theory and the novel mechanism of ionic conductivity proposed by Ito and Kamimura. The conductivity below the phase transition temperature can be explained by the following theoretical results: firstly, below T < T c, in the presence of an alternating electric field the ferroelastic phase changes to a new stripe phase consisting of the stripe domains in which the distances between XO4 groups are the same and of the intervening regions in which XO4 groups form XO4-H-XO4 dimers by hydrogen bonds; secondly, the stripe domains contribute to the ionic conductivity for T ≤ T c; thirdly, the propagation of protons along the zigzag paths in the stripe domains lead to the (Tc-T)−½ power law in the temperature dependence of the ionic conductivity.

A novel approach to the mechanism of ionic conductivity below and at the ferroelastic phase transition in the zero-dimensional hydrogen-bonded crystals M3H(X04)2 with (M = Rb or Cs; X = S or Se)

Abstract The temperature dependence of the proton conductivity in M3H(X04)2 (M = Rb or Cs; X = S or Se) is calculated for the low-conducting ferroelastic phase near the phase transition temperature, based on the phase transition theory and the novel mechanism of ionic conductivity proposed by Ito and Kamimura. The conductivity below the phase transition temperature can be explained by the following theoretical results: firstly, below T < T c, in the presence of an alternating electric field the ferroelastic phase changes to a new stripe phase consisting of the stripe domains in which the distances between XO4 groups are the same and of the intervening regions in which XO4 groups form XO4-H-XO4 dimers by hydrogen bonds; secondly, the stripe domains contribute to the ionic conductivity for T ≤ T c; thirdly, the propagation of protons along the zigzag paths in the stripe domains lead to the (Tc-T)−½ power law in the temperature dependence of the ionic conductivity.

Non-extensivity effects and the highest energy cosmic ray affair

Recent measurements of the cosmic microwave background confirm that it is described by a Planckian distribution with high precision. It is non-extensivity bounded to be less than some parts in 10 5, or to some parts in 10 4 at most. This deviation may appear minuscule, but may have a non-negligible effect on a particle propagating through this background over the course of millions of years. In this Letter we analyze the possible influence of such a slight deviation upon the propagation of nuclei and protons of ultra-high energy. These particles interact via photopion and photodisintegration processes which we examine taking into account a slight non-extensive background. We show that such a deviation does not exhibit a significant difference in the energy attenuation length of extremely high energy cosmic rays.

Simple method for solving transport equations describing the propagation of cosmic-ray nucleons in the atmosphere

A simple and efficient method is proposed for solving transport equations that describe the propagation of cosmic-ray protons and neutrons in the atmosphere at high energies. It is shown that, upon taking into account a non-power-law character of the primary spectrum, a growth of total cross sections for inelastic nucleon-nucleus interactions, and violation of scaling in such interactions, the effective absorption ranges of nucleons come to be dependent not only on energy but also on the depth in the atmosphere. The results of the calculations are compared with available experimental data.

Propagation of ultrahigh energy protons in the nearby universe

We present a new calculation of the propagation of protons with energies above $10^{19}$ eV over distances of up to several hundred Mpc. The calculation is based on a Monte Carlo approach using the event generator SOPHIA for the simulation of hadronic nucleon-photon interactions and a realistic integration of the particle trajectories in a random extragalactic magnetic field. Accounting for the proton scattering in the magnetic field affects noticeably the nucleon energy as a function of the distance to their source and allows us to give realistic predictions on arrival energy, time delay, and arrival angle distributions and correlations as well as secondary particle production spectra.

Interacting and interplanetary high-energy protons in solar flare events

We have compared the intensity-time profiles of the pion-related γ-ray emission (∼70 MeV) and the high-energy interplanetary solar protons in the 1990 May 24 and 1982 June 3 solar flare events. The results of the analysis of these events clearly indicate that the bulk of the interacting and interplanetary high-energy solar protons were not accelerated at the same time and in the same location at or near the Sun. Taking into account the different propagation times, the peak γ-ray emission in the 1990 May 24 event occurred ∼20 min. before the maximum intensity of the high-energy interplanetary protons. In the 1982 June 3 flare event the maximum γ-ray emission occurred at least 15 min before the intensity maximum of the interplanetary protons. Comparisons of the long-duration pion-related γ-ray emissions with the >355 MeV solar proton increases near the Earth in the 1991 June 11 and 15 solar flare events are inconclusive because the propagation of the interplanetary solar protons was diffusive.