Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “COSMIC ELECTRONS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Dipole anisotropy in cosmic electrons and positrons: inspection on local sources

The cosmic electrons and positrons have been measured with unprecedented statistics up to several hundreds GeV, thus permitting to explore the role that close single sources can have in shaping the flux at different energies. In the present analysis, we consider electrons and positrons in cosmic rays to be produced by spallations of hadron fluxes with the interstellar medium, by a smooth Supernova Remnant (SNR) population, by all the ATNF catalog pulsars, and by few discrete, local SNRs. We test several source models on the e {sup ++} e {sup −} and e {sup +} AMS-02 flux data. For the configurations compatible with the data, we compute the dipole anisotropy in e {sup ++} e {sup −}, e {sup +}, e {sup +}/ e {sup −} from single sources. Our study includes a dedicated analysis to the Vela SNR. We show that Fermi -LAT present data on dipole anisotropy of e {sup ++} e {sup −} start to explore some of the models for the Vela SNR selected by AMS-02 flux data. We also investigate how the observed anisotropy could result from a combination of local sources. Our analysis shows that the search of anisotropy in the lepton fluxes up to TeV energies can be an interesting tool for the inspection of properties of close SNRs, complementary to the high precision flux data.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

An ab initio model for the modulation of galactic cosmic-ray electrons

The modulation of galactic cosmic-ray electrons is studied using an ab initio three-dimensional steady state cosmic-ray modulation code in which the effects of turbulence on both the diffusion and drift of these cosmic-rays are treated as self-consistently as possible. A significant refinement is that a recent two-component turbulence transport model is used. This model yields results in reasonable agreement with observations of turbulence quantities throughout the heliosphere. The sensitivity of computed galactic electron intensities to choices of various turbulence parameters pertaining to the dissipation range of the slab turbulence spectrum, and to the choice of model of dynamical turbulence, is demonstrated using diffusion coefficients derived from the quasi-linear and extended nonlinear guiding center theories. Computed electron intensities and latitude gradients are also compared with spacecraft observations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Perspective on the Cosmic-ray Electron Spectrum above TeV

The AMS-02 has measured the cosmic-ray electron (plus positron) spectrum up to ∼TeV with unprecedented precision. The spectrum can be well described by a power law without any obvious features above 10 GeV. The satellite instrument Dark Matter Particle Explorer (DAMPE), which was launched a year ago, will measure the electron spectrum up to 10 TeV with high-energy resolution. The cosmic electrons beyond TeV may be attributed to few local cosmic-ray sources, such as supernova remnants. Therefore, spectral features, such as cut-off and bumps, can be expected at high energies. In this work, we provide a careful study on the perspective of the electron spectrum beyond TeV. We first examine our astrophysical source models on the latest leptonic data of AMS-02 to give a self-consistent picture. Then we focus on the discussion about the candidate sources, which could be electron contributors above TeV. Depending on the properties of the local sources (especially on the nature of Vela), DAMPE may detect interesting features in the electron spectrum above TeV in the future.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Suzaku observation of the Fermi cygnus cocoon: The search for a signature of young cosmic-ray electrons

The origin of Galactic cosmic rays remains unconfirmed, but promising candidates for their sources are found in star-forming regions. We report a series of X-ray observations, with Suzaku, toward the nearby star-forming region of Cygnus X. They aim at comparing diffuse X-ray emissions on and off the γ-ray cocoon of hard cosmic rays revealed by the Fermi Large Area Telescope. After excluding point sources and small-scale structures and subtracting the non-X-ray and cosmic X-ray backgrounds, the 2–10 keV X-ray intensity distribution is found to monotonically decrease with increasing Galactic latitude. This indicates that most of the extended emission detected by Suzaku originates from the Galactic ridge. In two observations, we derive upper limits of 3.4×10{sup −8} and 1.3×10{sup −8} erg s{sup −1} cm{sup −2} sr{sup −1} to X-ray emission in the 2–10 keV range from the γ-ray cocoon. These limits exclude the presence of cosmic-ray electrons with energies above about 50 TeV at a flux level capable of explaining the γ-ray spectrum. They are consistent with the emission cut-off observed near a TeV in γ-rays. The properties of the Galactic-ridge and local diffuse X-rays are also discussed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Probing the astrophysical origin of high-energy cosmic-ray electrons with Monte Carlo simulation

High-energy cosmic-ray electrons reveal some remarkable spectral features, the most noteworthy of which is the rise in the positron fraction above 10 GeV. Due to strong energy loss during propagation, these particles can reach Earth only from nearby sources. Yet, the exact nature of these sources, which most likely manifest themselves in the observed anomalies, remains elusive. The many explanations put forward to resolve this case range from standard astrophysics to exotic physics. In this paper, we discuss the possible astrophysical origin of high-energy cosmic-ray electrons through a fully three-dimensional time-dependent Monte Carlo simulation. This approach, which takes advantage of the intrinsic random nature of cosmic-ray diffusive propagation, provides valuable information on the electron-by-electron fluctuations, making it particularly suitable for analyzing in depth the single-source scenario.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Search for Cosmic-Ray Electron and Positron Anisotropies with Seven Years of Fermi Large Area Telescope Data

We present the Large Area Telescope on board the Fermi Gamma-ray Space Telescope that has collected the largest ever sample of high-energy cosmic-ray electron and positron events since the beginning of its operation. Potential anisotropies in the arrival directions of cosmic-ray electrons or positrons could be a signature of the presence of nearby sources. We use almost seven years of data with energies above 42 GeV processed with the Pass 8 reconstruction. The present data sample can probe dipole anisotropies down to a level of 10 -3 . We take into account systematic effects that could mimic true anisotropies at this level. We present a detailed study of the event selection optimization of the cosmic-ray electrons and positrons to be used for anisotropy searches. Since no significant anisotropies have been detected on any angular scale, we present upper limits on the dipole anisotropy. Lastly, the present constraints are among the strongest to date probing the presence of nearby young and middle-aged sources.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Connecting direct and indirect detection with a dark spike in the cosmic-ray electron spectrum

Multiple space-borne cosmic ray detectors have detected line-like features in the electron and positron spectra. Most recently, the DAMPE collaboration reported the existence of such a feature at 1.4 TeV, sparking interest in a potential dark matter origin. Such quasi-monochromatic features, virtually free of any astrophysical background, could be explained by the annihilation of dark matter particles in a nearby dark matter clump. Here, we explore the consistency of producing such spectral features with dark matter annihilation from the standpoint of dark matter substructure statistics, constraints from anisotropy, and constraints from gamma-ray emission. We demonstrate that if indeed a high-energy, linelike feature in the electron-positron spectrum originates from dark matter annihilation in a nearby clump, a significant or even dominant fraction of the dark matter in the Solar System likely stems from the clump, with dramatic consequences for direct dark matter searches.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

SPECTRA OF COSMIC RAY ELECTRONS AND DIFFUSE GAMMA RAYS WITH THE CONSTRAINTS OF AMS-02 AND HESS DATA

Recently, AMS-02 reported their results of cosmic ray (CR) observations. In addition to the AMS-02 data, we add HESS data to estimate the spectra of CR electrons and the diffuse gamma rays above TeV. In the conventional diffusion model, a global analysis is performed on the spectral features of CR electrons and the diffuse gamma rays by the GALRPOP package. The results show that the spectrum structure of the primary component of CR electrons cannot be fully reproduced by a simple power law and that the relevant break is around 100 GeV. At the 99% confidence level (C.L.) the injection indices above the break decrease from 2.54 to 2.35, but the ones below the break are only in the range of 2.746–2.751. The spectrum of CR electrons does not need to add TeV cutoff to also match the features of the HESS data. Based on the difference between the fluxes of CR electrons and their primary components, the predicted excess of CR positrons is consistent with the interpretation that these positrons originate from a pulsar or dark matter. In the analysis of the Galactic diffuse gamma rays with the indirect constraint of AMS-02 and HESS data, it is found that the fluxes of Galactic diffuse gamma rays are consistent with the GeV data of the Fermi-Large Area Telescope (LAT) in the high-latitude regions. The results indicate that inverse Compton scattering is the dominant component in the range of hundreds of GeV to tens of TeV, respectively from the high-latitude regions to the low ones, and in all of the regions of the Galaxy the flux of diffuse gamma rays is less than that of CR electrons at the energy scale of 20 TeV.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Polarization of the Sunyaev-Zel'dovich effect: relativistic imprint of thermal and non-thermal plasma

Inverse Compton (IC) scattering of the anisotropic CMB fluctuations off cosmic electron plasmas generates a polarization of the associated Sunyaev-Zel'dovich (SZ) effect. The polarized SZ effect has important applications in cosmology and in astrophysics of galaxy clusters. However, this signal has been studied so far mostly in the non-relativistic regime which is valid only in the very low electron temperature limit for a thermal electron population and, as such, has limited astrophysical applications. Partial attempts to extend this calculation to the IC scattering of a thermal electron plasma in the relativistic regime have been done but these cannot be applied to a more general or mildly relativistic electron distribution. In this paper we derive a general form of the SZ effect polarization that is valid in the full relativistic approach for both thermal and non-thermal electron plasmas, as well as for a generic combination of various electron population which can be co-spatially distributed in the environments of galaxy clusters or radiogalaxy lobes. We derive the spectral shape of the Stokes parameters induced by the IC scattering of every CMB multipole for both thermal and non-thermal electron populations, focussing in particular on the CMB quadrupole and octupole that provide the largest detectable signals in cosmic structures (like galaxy clusters). We found that the CMB quadrupole induced Stoke parameter Q is always positive with a maximum amplitude at a frequency ≈ 216 GHz which increases non-linearly with increasing cluster temperature. On the contrary, the CMB octupole induced Q spectrum shows a cross-over frequency which depends on the cluster electron temperature in a linear way, while it shows a non-linear dependence on the minimum momentum p {sub 1} of a non-thermal power-law spectrum as well as a linear dependence on the power-law spectral index of the non-thermal electron population. We discuss some of the possibilities to disentangle the quadrupole-induced Q spectrum from the octupole-induced one which will allow to measure these important cosmological quantities through the SZ effect polarization at different cluster locations in the universe. We finally apply our model to the Bullet cluster and derive the visibility windows of the total, quandrupole-induced and octupole-induced Stoke parameter Q in the frequency ranges accessible to SKA, ALMA, MILLIMETRON and CORE++ experiments.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Cosmic-ray electron-positron spectrum from 7 GeV to 2 TeV with the Fermi Large Area Telescope

Here, we present a measurement of the cosmic-ray electron+positron spectrum between 7 GeV and 2 TeV performed with almost seven years of data collected with the Fermi Large Area Telescope. We find that the spectrum is well fit by a broken power law with a break energy at about 50 GeV. Above 50 GeV, the spectrum is well described by a single power law with a spectral index of 3.07 ± 0.02(stat + syst) ± 0.04(energy measurement). An exponential cutoff lower than 1.8 TeV is excluded at 95% CL.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

The Mu2e crystal calorimeter and improvements in the $\mu^-\mbox{N} \to e^-\mbox{N}$ search sensitivity

The Mu2e experiment will search for Charged Lepton Flavor Violation (CLFV) looking at the conversion of a muon into an electron in the field of an aluminum nucleus. About $7\cdot 10^{17}$ muons, provided by a dedicated muon beam line in construction at the Fermi National Accelarator Laboratory (Fermilab), will be stopped in 3 years in the Aluminum target. The corresponding single event sensitivity will be $2.5\cdot 10^{-17}$. The Standard Model of particle physics, even extendend to include the finite neutrino masses, predicts the ratio R μe between muon conversions and muon nuclear captures to be $\sim 10^{- 52}$. Several extensions of the Standard Model predict R μe to be in the range of $10^{-14} - 10^{-18}$. % The current best experimental limit, set by the SINDRUM II experiment is $7 \cdot 10^{-13}$ @ $90\%$ CL. The Mu2e experiment plans to improve this experimental limit by four order of magnitude to test many of the possible extensions of the Standard Model. To reach this ambitious goal, the Mu2e experiment is expected to use an intense pulsed muon beam, and rely on a detector system composed of a straw tube tracker and a calorimeter made of pure CsI crystals. The calorimeter plays a central role in the Mu2e measurement, providing particle identification capabilities that are necessary for rejecting two of the most dangerous background sources that can mimic the μ⁻N → e⁻N conversion electron: cosmic muons and $\bar{p}$ induced background. The calorimeter information allows also to improve the tracking performance. Thanks to a calorimeter-seeded track finder algorithm, it is possible to increase the track reconstruction efficiency, and make it more robust with respect to the occupancy level. Expected performances of the calorimeter have been studied in a beam test at the Beam Test Facility in Frascati (Rome, Italy). A reduced scale calorimeter prototype has been exposed to an electron beam, with energy varying from 80 to 140 MeV, for measuring the timing resolution and validate the Monte Carlo prediction. A timing resolution $\sigma_{\rm t}<200$ ps @ 100 MeV has been obtained. Combination of the background rejection performance, and the improvements in the track reconstruction, have then been used in the calculation of the expected Mu2e sensitivity.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

A SELF-CONSISTENT EXPLANATION OF TeV EMISSIONS FROM HESS J1640-465 AND HESS J1641-463

The bright TeV source HESS J1640-465 is positionally coincident with the young supernova remnant (SNR) G338.3-0.0, and the nearby HESS J1641-463 with TeV gamma-ray emission seems to be closely associated with it. Based on the nonlinear diffusion shock acceleration model, we explore the emission from these two TeV sources, the particle diffusion is assumed to be different inside and outside the absorbing boundary of the particles accelerated in the SNR shock. The results indicate that (1) the GeV–TeV emission from the region of the HESS J1640-465 is produced as a result of the particle acceleration inside the SNR G338.3-0.0 and (2) the runaway cosmic-ray particles outside the SNR are interacting with the nearby dense molecular cloud (MC) at the region of the HESS J1641-463, corresponding π{sup 0} decay gamma-ray in proton–proton collision contribute to the TeV emission from the HESS J1641-463. Also, we investigate the possible X-ray emission in MC from the synchrotron procedure by secondary e{sup ±} produced through escaped protons interaction with the MC.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Quick spacecraft charging primer

This is a presentation in PDF format which is a quick spacecraft charging primer, meant to be used for program training. It goes into detail about charging physics, RBSP examples, and how to identify charging.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

BOW TIES IN THE SKY. I. THE ANGULAR STRUCTURE OF INVERSE COMPTON GAMMA-RAY HALOS IN THE FERMI SKY

Extended inverse Compton halos are generally anticipated around extragalactic sources of gamma rays with energies above 100 GeV. These result from inverse Compton scattered cosmic microwave background photons by a population of high-energy electron/positron pairs produced by the annihilation of the high-energy gamma rays on the infrared background. Despite the observed attenuation of the high-energy gamma rays, the halo emission has yet to be directly detected. Here, we demonstrate that in most cases these halos are expected to be highly anisotropic, distributing the upscattered gamma rays along axes defined either by the radio jets of the sources or oriented perpendicular to a global magnetic field. We present a pedagogical derivation of the angular structure in the inverse Compton halo and provide an analytic formalism that facilitates the generation of mock images. We discuss exploiting this fact for the purpose of detecting gamma-ray halos in a set of companion papers.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Observing signals of spectral features in the cosmic-ray positrons and electrons from Milky Way pulsars

The Alpha Magnetic Spectrometer (AMS-02) has provided unprecedented precision measurements of the electron and positron cosmic-ray fluxes and the positron fraction spectrum. At the higher energies, sources as energetic local pulsars, may contribute to both cosmic-ray species. The discreteness of the source population, can result in features both on the positron fraction measurement and in the respective electron and positron spectra. For the latter, those would coincide in energy and would contrast predictions of smooth spectra as from particle dark matter. In this work, using a library of pulsar population models for the local part of the Milky Way, we perform a power-spectrum analysis on the cosmic-ray positron fraction. We also develop a technique to cross-correlate the electron and positron fluxes. We show that both such analyses, can be used to search statistically for the presence of spectral wiggles in the cosmic-ray data. For a significant fraction of our pulsar simulations, those techniques are already sensitive enough to give a signal for the presence of those features above the regular noise, with forthcoming observations making them even more sensitive. Lastly, by cross-correlating the AMS-02 electron and positron spectra, we find an intriguing first hint for a positive correlation between them, of the kind expected by a population of local pulsars.

79 ASTRONOMY AND ASTROPHYSICS↗