Ray Electrons Research Articles

Observations of the gamma-ray emission from the Quiescent Sun with Fermi Large Area Telescope during the first 7 years in orbit

The high energy gamma-ray emission from the quiescent Sun is due to the interactions of cosmic ray (CR) protons and electrons with matter and photons in the solar environment. Such interactions lead to two component gamma-ray emission: a disk-like emission due to the nuclear interactions of CR protons and nuclei in the solar atmosphere and a space extended emission due to the inverse Compton (IC) scattering of CR electrons off solar photons in the whole heliosphere. The observation of these two solar emission components may give useful information about the evolution of the solar cycle by probing two different CR components (proton and electrons) in regions not directly accessible by direct observations. We present the results of the observations of the Sun with Fermi-LAT in the first 7 years on orbit, with the exception of the flaring periods. Significantly large photon statistics and improved processing performance with respect to previous analysis allow us to explore both components of the emission in greater details and perform better comparisons of data with current models of the IC component. This allows us to probe CR electrons in the inner heliosphere which is not possible by other methods. Moreover, the longer period of observations allows us to study the variations of the emission between the maximum and the minimum of the solar cycle.

Recent results from the AMS-02 experiment

The AMS-02 detector is a large acceptance magnetic spectrometer operating onboard the International Space Station since May 2011. The main goals of the detector are the search for antimatter and dark matter in space, as well as the measurement of cosmic ray composition and flux. Precise measurements of cosmic ray positrons and electrons are presented in this document, based on 41×10 9 events collected during the first 30 months of operations.

FARADAY DISPERSION FUNCTIONS OF GALAXIES

The Faraday dispersion function (FDF), which can be derived from an observed polarization spec- trum by Faraday rotation measure synthesis, is a profile of polarized emissions as a function of Faraday depth. We study intrinsic FDFs along sight lines through face-on, Milky-Way-like galaxies by means of a sophisticated galactic model incorporating 3D MHD turbulence, and investigate how much the FDF contains information intrinsically. Since the FDF reflects distributions of thermal and cosmic- ray electrons as well as magnetic fields, it has been expected that the FDF could be a new probe to examine internal structures of galaxies. We, however, find that an intrinsic FDF along a sight line through a galaxy is very complicated, depending significantly on actual configurations of turbulence. We perform 800 realizations of turbulence, and find no universal shape of the FDF even if we fix the global parameters of the model. We calculate the probability distribution functions of the standard deviation, skewness, and kurtosis of FDFs and compare them for models with different global pa- rameters. Our models predict that the presence of vertical magnetic fields and large scale-height of cosmic-ray electrons tend to make the standard deviation relatively large. Contrastingly, differences in skewness and kurtosis are relatively less significant.

The possibilities of simultaneous detection of gamma rays, cosmic-ray electrons and positrons on the GAMMA-400 space observatory

The GAMMA-400 space observatory will pro- vide precise measurements of gamma rays, electrons, and positrons in the energy range 0.1-3000 GeV. The good an- gular and energy resolutions, as well as identification capa- bilities (angular resolution 0.01 , energy resolution 1%, and proton rejection factor 10 6 ) will allow us to study the main galactic and extragalactic sources, diffuse gamma-ray background, gamma-ray bursts, and to measure electron and positron fluxes. The peculiar characteristics of the experi- ment is simultaneous detection of gamma rays and cosmic- ray electrons and positrons, which can be connected with an- nihilation or decay of dark matter particles.

Protohalo constraints to the resonant annihilation of dark matter

It has recently been argued that the PAMELA, ATIC, and PPB-BETS data showing an anomalous excess of high-energy cosmic ray positrons and electrons might be explained by dark matter annihilating in the Galactic halo with a cross section resonantly enhanced compared to its value in the primeval plasma. We find that with a very large annihilation cross section the flash of energetic photons and electron-positron pairs expected from dark-matter annihilation in the first protohalos that form at redshift $z\ensuremath{\sim}40$ is likely substantial and observable. As a consequence, bounds on the allowed energy injection into the primordial gas and the energy density of the diffuse gamma-ray background give rise to limits on the low-velocity dark-matter cross section that can be difficult to reconcile with this interpretation of the PAMELA, ATIC, and PPB-BETS results.

Can Galactic γ-Ray Background be due to Superposition of γ-Rays from Millisecond Pulsars?

The SAS 2 and COS B observations have established the existence of diffuse γ-rays in our Galaxy in various energy ranges. The diffuse radiation is attributed to the interaction of cosmic ray nuclei and electrons with the particles of interstellar atomic and molecular gas (via the decay of pions and bremsstrahlung, respectively). Inverse Compton scattering of interstellar photons by the high energy electrons of cosmic rays may also be contributing to this background. In addition some contribution may come from discrete sources of γ-rays.

Double-Beta Decay

In a double-beta event, two neutrons decay simultaneouly into two protons, two beta rays (electrons) and two antineutrinos. Experimentalists are now searching for another form of double-beta decay, one that does not produce neutrinos or antineutrinos. If such an event is found, it could unravelone of nature's great mysteries: What, if anything, is the mass of the neutrino According to the Standard Model, the neutrino accompanying a negative beta ray is the distinct antiparticle of the one accompanying a positive beta ray. The theories that go beyond the Standard Model and assign a mass to the neutrino, however, predict that the particle emitted with a negative beta ray should be the same as the one emitted with a positive ray. In other words, the neutrino would be its own antiparticle. How can we tell whether these predictions are right Double-beta decay is the ideal process in which to seek an answer to this question. If the neutrino has mass and is its own antiparticle, then the neutrino emitted in the first stage of the process might be reaborbed in the second, yielding a form of decay in which no neutrinos materialize. 8 figs.

Response of Barium-Fluoride Plastic Scintillator to Light Particles and Particle Identification

We have tested BPS for protons, deuterons and alpha particles and showd that BPS has a capability for particle identification. We have also shown, for the first time, that there is a close parallel in the behavior of BPS(BaF2 crystal), plastic scintillator. anthracene, BGO, NaI(Tl) and liquid scintillator toward the scintillation efficiencies. This behavior was explained by introducing the truck structure and the thermalization distance of ?-ray electrons.

Relativistic study of K-shell x-ray and Auger-electron energy shifts for additional atomic vacancies.

The hydrogenic model of Burch et al. for calculating the energy shifts of the K x ray and Auger electrons for a vacancy in the L shell is extended to incorporate the effect of relativity. Numerical results are presented for 18 values of Z (from 10 to 95 in steps of 5). The computations are based on two different choices of the screening parameters. The effective nuclear charges (${Z}_{\mathrm{eff})}$ determined by the method of O'Connell and Carroll yield numbers for the energy shifts close to the predictions of Hartree-Fock (HF) and Hartree-Fock-Slater (HFS) calculations. On the other hand, ${Z}_{\mathrm{eff}}$ obtained from Slater's rule gives numbers which are considerably larger than the HF and HFS values. However, the choice of screening is crucial only for low-Z elements and relativity plays an increasingly dominant role as one goes to higher atomic numbers. It is found that the relativistic effect is more pronounced for a vacancy in the ${L}_{2}$ subshell.

On the Origin of the Nonthermal Radio Emission at 0.4-6.5 MHz

view Abstract Citations (6) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Origin of the Nonthermal Radio Emission at 0.4-6.5 MHz Lerche, I. Abstract Two explanations of the observed high-intensity, low-frequency nonthermal radio emission have been suggested in the literature. The first, which postdated the observations, is synchrotron radiation from cosmi&ray electrons in the Galaxy; the second, which predated the observations, is enhanced bremsstrahlung at 1 and 2 times the plasma frequency of a discrete source. In this paper we examine both mechanisms in some detail. We find that it is unlikely that synchrotron radiation by cosmic-ray electrons causes the low-frequency emission in 0. 3 MHz because the interstellar plasma gives a Razin absorption edge which, for numbers currently acceptable for the interstellar medium, is about 0.8 MHz- well above 0A MHz where, in fact, radiation is observed. On the other hand, the predicted level, and spectrum, of enchanced bremsstrahlung from a discrete nonthermal radio source agree well with the observed radiation. This predicted radiation gives a consistent picture of the low-frequency emission in the band 0.4 to 5 MHz. Above 5 MHz the broad-band synchrotron emission from cosmic-ray electrons appears to dominate the narrow-band, discrete-source, bremsstrahlung radiation. Publication: The Astrophysical Journal Pub Date: June 1971 DOI: 10.1086/150960 Bibcode: 1971ApJ...166..311L full text sources ADS |

Discussion of paper by W. R. Webber and C. Chotkowski, ‘A determination of the energy spectrum of extraterrestrial electrons in the energy range 70-2000 Mev’

In a series of papers [Webber and Chotkowski, 1967a, b; Beedle and Webber, 1968; Webber, 1968; Rockstroh and Webber, 1969], Webber and his collaborators have published results on the energy spectrum of cosmic ray and atmospheric electrons. These results were based on measurements with a lead glass Cerenkov counter for energy determination of the electrons. In the absence of a direct calibration of their instrument, the authors used data of Heusch and Prescott [1964] to determine the energy response of the detector in relation to penetrating, highly relativistic, single charged particles.

Auger and secondary X -ray electrons from gold

When a target of any element is bombarded with X-rays, the electrons emitted from its surface fall into two groups, sometimes called photoelectrons of the first and second kind respectively. Each group, when analysed by a magnetic field, yields a fairly complex velocity spectrum. Those of the first group, for which we shall use the convenient term, introduced by Whiddington in 1922, of “X-ray electrons”, are the electrons ejected from different X-ray levels of the element by the direct action of a quantum of the incident X-radiation. Their energies are given by a simple modification of the Einstein photoelectric equation, the characteristic critical absorption frequencies of the element taking the place usually occupied in that equation by the photoelectric threshold frequency. The electrons of the second group arise, in atoms which have lost an X-ray electron, as the result of more or less complicated internal “radiationless” rearrangements of the extranuclear structure. As the atom from which they emerge is left multiply ionized in its X-ray levels, no simple expression can be written down for the electron energies. Photoelectrons of this kind were detected in 1914 by Robinson and Rawlinson, but at that date it was not possible to account for their origin. They were investigated and interpreted by de Broglie in 1921 and in somewhat greater detail by Robinson and Cassie in 1925-6. The clearest and most unequivocal evidence of their mode of origin was, however, given by Auger’s beautiful cloud-chamber experiments, and these electrons are therefore generally known as “Auger electrons” .