Intergalactic Magnetic Field Strength Research Articles

Discrepancies between Predicted and Observed Intergalactic Magnetic Field Strengths from the Universe’s Total Energy: Is it Contained within Submatter Spatial Geometry?

Although the gravitational energy within the distance of the radius of a singularity for a current estimated mass of the universe is equal to ~1069 Joules, congruent solutions for different ages of the universe reflect changes by a factor of π or 8π for identities. The total energy value is equal to the product of primary constants G·μ·ε·ħ·σ·c2 (which results in power, W) when divided by the area of smallest unit of space (area of a circle with a radius of Planck’s Length) and then multiplied by the universe’s current surface area and age. The conspicuous discrepancies of ~2∙103 between the predicted average magnetic intensity within the universe from that total energy and contemporary measurements can be accommodated by the quantitative product of 21.3π4 derived from the classic four-dimensional metric. The equivalent electric field potential divided by the predicted magnetic intensity results in a velocity that has been suggested to reflect the latency for excess correlations to occur across the universe. The most parsimonious explanation for these results is that a large component of the magnetic manifestation of energy in the universe is recondite or occluded within its submatter spatial structure and that the required cohesion or “diffusivity” throughout the volume involves the electric field component. These quantifications may facilitate understanding of Mach’s principle that any part of the universe is influenced by all of its parts.

Discrepancies between Predicted and Observed Intergalactic Magnetic Field Strengths from the Universe’s Total Energy: Is it Contained within Submatter Spatial Geometry?

Although the gravitational energy within the distance of the radius of a singularity for a current estimated mass of the universe is equal to ~1069 Joules, congruent solutions for different ages of the universe reflect changes by a factor of π or 8π for identities. The total energy value is equal to the product of primary constants G·μ·ε·ħ·σ·c2 (which results in power, W) when divided by the area of smallest unit of space (area of a circle with a radius of Planck’s Length) and then multiplied by the universe’s current surface area and age. The conspicuous discrepancies of ~2∙103 between the predicted average magnetic intensity within the universe from that total energy and contemporary measurements can be accommodated by the quantitative product of 21.3π4 derived from the classic four-dimensional metric. The equivalent electric field potential divided by the predicted magnetic intensity results in a velocity that has been suggested to reflect the latency for excess correlations to occur across the universe. The most parsimonious explanation for these results is that a large component of the magnetic manifestation of energy in the universe is recondite or occluded within its submatter spatial structure and that the required cohesion or “diffusivity” throughout the volume involves the electric field component. These quantifications may facilitate understanding of Mach’s principle that any part of the universe is influenced by all of its parts.

THE INFLUENCE OF PLASMA EFFECTS OF PAIR BEAMS ON THE INTERGALACTIC CASCADE EMISSION OF BLAZARS

The attenuation of TeV γ-rays from distant blazars by the extragalactic background light (EBL) produces relativistic electron-positron pair beams. It has been shown by Broderick et. al. (2012) and Schlickeiser et. al (2012) that a pair beam traversing the intergalactic medium is unstable to linear two-stream instabilities of both electrostatic and electromagnetic nature. While for strong blazars all free pair energy is dissipated in heating the intergalactic medium and a potential electromagnetic cascade via inverse-Compton scattering with the cosmic microwave background is suppressed, we investigate the case of weak blazars where the back reaction of generated electrostatic turbulence leads to a plateauing of the electron energy spectrum. In the ultra-relativistic Thomson limit we analytically calculate the inverse-Compton spectral energy distribution for both an unplateaued and a plateaued beam scenario, showing a peak reduction factor of Rpeak ≈ 0.345. This is consistent with the FERMI non-measurements of a GeV excess in the spectrum of EBL attenuated TeV blazars. Claims on the lower bound of the intergalactic magnetic field strengths, made by several authors neglecting plasma effects, are thus put into question.

Probing the intergalactic magnetic field with the anisotropy of the extragalactic gamma-ray background

The intergalactic magnetic field (IGMF) may leave an imprint on the angular anisotropy of the extragalactic gamma-ray background through its effect on electromagnetic cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will deflect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thereby inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Here we present a simple, proof-of-concept calculation of the magnitude of this effect and demonstrate that current Fermi data already seem to prefer non-negligible IGMF values. The anisotropy energy spectrum of the Fermi gamma-ray background could thus be used as a probe of the IGMF strength.

Constraints on the intergalactic magnetic field from gamma-ray observations of TeV blazars

We discuss different approaches to infer the properties of the intergalactic magnetic field (IGMF) from gamma-ray observations of blazars. In particular, we investigate constraints on the IGMF strength and spacial distribution, resulting from studies of TeV blazars by imaging atmospheric Cherenkov telescopes and the Fermi-LAT instrument. We demonstrate that the non-observation of GeV gamma-rays from powerful TeV blazars indicates that more than 60% of space is filled by magnetic fields with stength ≳ 10−15 G, favoring the primordial IGMF origin.

Spontaneous magnetization of the vacuum and the strength of the magnetic field in the hot Universe

Intergalactic magnetic fields are assumed to have been spontaneously generated at the reheating stage of the early Universe, due to vacuum polarization of non-Abelian gauge fields at high temperature. The fact that the screening mass of this type of fields has zero value was discovered recently. A procedure to estimate their field strengths, $B(T)$, at different temperatures is here developed, and the value $B(T_{ew}) \sim 10^{14} G$ at the electroweak phase transition temperature, is derived by taking into consideration the present value of the intergalactic magnetic field strength, $B_0 \sim 10^{- 15} G$, coherent on the $\sim 1$ Mpc scale. As a particular case, the standard model is considered and the field scale at high temperature is estimated in this case. Model dependent properties of the phenomena under investigation are briefly discussed, too.

Gamma-ray halos as a measure of intergalactic magnetic fields: A classical moment problem

The presence of weak intergalactic magnetic fields can be studied by their effect on electromagnetic cascades induced by multi-TeV $\ensuremath{\gamma}$ rays in the cosmic radiation background. Small deflections of secondary electrons and positrons as the cascade develops extend the apparent size of the emission region of distant TeV $\ensuremath{\gamma}$-ray sources. These $\ensuremath{\gamma}$-ray halos can be resolvable in imaging atmospheric Cherenkov telescopes and serve as a measure of the intergalactic magnetic field strength and coherence length. We present a method of calculating the $\ensuremath{\gamma}$-ray halo for isotropically emitting sources by treating magnetic deflections in the cascade as a diffusion process. With this ansatz the moments of the halo follow from a set of simple diffusion-cascade equations. The reconstruction of the angular distribution is then equivalent to a classical moment problem. We present a simple solution using Pad\'e approximations of the moment's generating function.

Hints of the existence of axionlike particles from the gamma-ray spectra of cosmological sources

Axionlike particles (ALPs) are predicted to couple with photons in the presence of magnetic fields. This effect may lead to a significant change in the observed spectra of gamma-ray sources such as active galactic nuclei (AGNs). Here we carry out a detailed study that for the first time simultaneously considers in the same framework both the photon/axion mixing that takes place in the gamma-ray source and that one expected to occur in the intergalactic magnetic fields. An efficient photon/axion mixing in the source always means an attenuation in the photon flux, whereas the mixing in the intergalactic medium may result in a decrement and/or enhancement of the photon flux, depending on the distance of the source and the energy considered. Interestingly, we find that decreasing the value of the intergalactic magnetic field strength, which decreases the probability for photon/axion mixing, could result in an increase of the expected photon flux at Earth if the source is far enough. We also find a 30% attenuation in the intensity spectrum of distant sources, which occurs at an energy that only depends on the properties of the ALPs and the intensity of the intergalactic magnetic field, and thus independent of the AGN source being observed. Moreover, we show that this mechanism can easily explain recent puzzles in the spectra of distant gamma-ray sources, like the possible detection of TeV photons from 3C 66A (a source located at $z=0.444$) by MAGIC and VERITAS, which should not happen according to conventional models of photon propagation over cosmological distances. Another puzzle is the recent published lower limit to the extragalactic background light intensity at $3.6\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ (which is almost twice larger as the previous one), which implies very hard spectra for some detected TeV gamma-ray sources located at $z=0.1--0.2$. The consequences that come from this work are testable with the current generation of gamma-ray instruments, namely Fermi (formerly known as GLAST) and imaging atmospheric Cherenkov telescopes like CANGAROO, HESS, MAGIC, and VERITAS.

Possible effects of pair echoes on gamma-ray burst afterglow emission

High-energy emission from gamma-ray bursts (GRBs) is widely expected but had been sparsely observed until recently when the Fermi satellite was launched. If >TeV gamma-rays are produced in GRBs and can escape from the emission region, they are attenuated by the cosmic infrared background photons, leading to regeneration of ∼GeV–TeV secondary photons via inverse-Compton scattering. This secondary emission can last for a longer time than the duration of GRBs, and it is called a pair echo. We investigate how this pair echo emission affects spectra and light curves of high-energy afterglows, considering not only prompt emission but also afterglow as the primary emission. Detection of pair echoes is possible as long as the intergalactic magnetic field (IGMF) in voids is weak. We find (1) that the pair echo from the primary afterglow emission can affect the observed high-energy emission in the afterglow phase after the jet break and (2) that the pair echo from the primary prompt emission can also be relevant, but only when significant energy is emitted in the TeV range, typically ⁠. Even non-detections of the pair echoes could place interesting constraints on the strength of IGMF. The more favourable targets to detect pair echoes may be the ‘naked’ GRBs without conventional afterglow emission, although energetic naked GRBs would be rare. If the IGMF is weak enough, it is predicted that the GeV emission extends to >30–300 s.

Towards Unravelling the Structural Distribution of Ultra-High-Energy Cosmic Ray Sources

We investigate the possibility that observations of ultra-high-energy cosmic-rays (UHECRs) in the near future may be able to unveil their local source distribution. We simulate the arrival distribution of UHE protons taking account of their propagation process in intergalactic magnetic field (IGMF) associated with the local structure actually observed around the Milky Way and investigate the similarity of the spatial patterns between the arrival distribution and the source distribution. We find that UHE protons above 10 19.8 eV are the best indicators for unravelling the source distribution within 100 Mpc, and the detection of about 500 events on the whole sky would realize the purpose for plausible IGMF strength and source number density. We also discuss the deflection of the trajectories of UHE protons by the Galactic magnetic field (GMF). In favored GMF models, the deflection angles are consistent with the angular scale of the positional correlation reported by the Pierre Auger Observatory except in th...

Possible GeV Emission from TeV Blazars

We propose a model to account for possible GeV emission from TeV blazars. In this model, the possible GeV emission from a TeV blazar can consist of two components. One, the source component, is produced in the source through the synchrotron self-Compton (SSC) mechanism; the other, the external component, is produced on the way from the source to us by the inverse Compton (IC) scattering of e± pairs with the cosmic microwave background (CMB), where the e± are created through the interaction of TeV gamma rays emitted from the TeV blazar with the diffuse IR-UV background. We apply the model to study the possible GeV emission from Mrk 501, which is a strong TeV emitter. We calculate self-consistently the spectra of high-energy gamma rays of these two components for three different activities of Mrk 501 in 1997. Our results indicate that (1) the GeV gamma-ray emission of the external component can dominate that of the source component if the intergalactic magnetic field (IGMF) strength is not greater than 10−19 G; (2) the shape of the photon spectra of the external component depends on both the observed variation time and the IGMF strength, particularly in the lower part of GeV energy range; (3) the flux level of TeV photons determines that of the spectrum of the external component; and (4) GeV emission from different activity in Mrk 501 should be detectable by the upcoming satellite GLAST.

GeV and Higher Energy Photon Interactions in Gamma‐Ray Burst Fireballs and Surroundings

We have calculated the opacities and secondary production mechanisms of high energy photons arising in gamma-ray burst internal shocks, using exact cross-sections for the relevant processes. We find that for reasonable choices of parameters, photons in the range of 10's to 100's of GeV may be emitted in the prompt phase. Photons above this range are subject to electron-positron pair production with fireball photons and would be absent from the spectrum escaping the gamma-ray burst. We find that, in such cases, the fireball becomes optically thin again at ultra-high energies ($\gtrsim$ PeV). On the other hand, for sufficiently large fireball bulk Lorentz factors, the fireball is optically thin at all energies. Both for $\gamma\gamma$ self-absorbed and optically thin cases, the escaping high energy photons can interact with infra-red and microwave background photons to produce delayed secondary photons in the GeV-TeV range. These may be observable with GLAST, or at low redshifts with ground-based air Cherenkov telescopes. Detection of the primary prompt spectrum constrains the bulk Lorentz factor, while detection of delayed secondary gamma-rays would provide a consistency check for the primary spectrum and the bulk Lorentz factor as well as constraints on the intergalactic magnetic field strength.

Strong GeV emission accompanying TeV blazar H1426+428

For High frequency BL Lac objects (HBLs) like H1426+428, a significant fraction of their TeV gamma-rays emitted are likely to be absorbed in interactions with the diffuse IR background, yielding e pairs. The resulting e pairs generate one hitherto undiscovered GeV emission by inverse Compton scattering with the cosmic microwave background photons (CMBPs). We study such emission by taking the 1998-2000 CAT data, the reanalyzed 1999 & 2000 HEGRA data and the corresponding intrinsic spectra proposed by Aharonian et al. ([CITE]). We numerically calculate the scattered photon spectra for different intergalactic magnetic field (IGMF) strengths. If the IGMF is about or weaker, there comes very strong GeV emission, whose flux is far above the detection sensitivity of the upcoming satellite GLAST! Considered its relatively high redshift (), the detected GeV emission in turn provides us a valuable chance to calibrate the poorly known spectral energy distribution of the intergalactic infrared background, or provides us some reliable constraints on the poorly known IGMF strength.

G[CLC]e[/CLC]V Emission from T[CLC]e[/CLC]V Blazars and Intergalactic Magnetic Fields

Several high-frequency peaked BL Lac objects such as Mrk 501 are strong TeV emitters. However, a significant fraction of the TeV gamma rays emitted are likely to be absorbed in interactions with the diffuse IR background, yielding electron-positron pairs. Hence, the observed TeV spectrum must be steeper than the intrinsic one. Using the recently derived intrinsic gamma-ray spectrum of Mrk 501 during its 1997 high state, we study the inverse Compton scattering of cosmic microwave photons by the resulting electron-positron pairs, which implies the existence of a hitherto undiscovered GeV emission. The typical duration of the GeV emission is determined by the flaring activity time and the energy-dependent magnetic deflection time. We numerically calculate the scattered photon spectrum for different intergalactic magnetic field (IGMF) strengths and find a spectral turnover and flare duration at GeV energies that are dependent on the field strength. We also estimate the scattered photon flux in the quiescent state of Mrk 501. The GeV flux levels predicted are consistent with existing EGRET upper limits and should be detectable above the synchrotron self-Compton component with the Gamma-Ray Large Area Space Telescope for IGMFs 10-16 G, as expected in voids. Such detections would provide constraints on the strength of weak IGMFs.

Identification of sources of ultrahigh energy cosmic rays

The arrival directions of extensive air showers with energies 4×1019 3σ (σ is the parameter of Gaussian distribution). The Seyfert galaxies are characterized by moderate luminosities (L 1014 eV recorded by the Bolivian and Tian Shan arrays. The source identifications suggest that the gamma rays could have been produced in interactions of cosmic rays with the microwave background radiation and subsequent electromagnetic cascades in intergalactic space. We estimate the strength of intergalactic magnetic fields outside galaxy clusters to be B≤8.7×10−10 G.

Signatures of the Origin of High-Energy Cosmic Rays in Cosmological Gamma-Ray Bursts

We derive observational consequences for the hypothesis that cosmic rays (CRs) of energy greater than 1019 eV originate in the same cosmological objects producing gamma-ray bursts (GRBs). Intergalactic magnetic fields 10-12 G are required in this model to allow CRs to be observed continuously in time by producing energy-dependent delays in the CR arrival times. This results in individual CR sources having very narrow observed spectra, since at any given time only those CRs having a fixed time delay are observed. Thus, the brightest CR sources should be different at different energies. The average number of sources contributing to the total CR flux decreases with energy much more rapidly than in a model of steady CR sources, dropping to one at Ecrit 2 × 1020 eV with very weak sensitivity to the intergalactic magnetic field strength. Below Ecrit, a very large number of sources is expected, consistent with observations. Above Ecrit, a source may be observed with a flux considerably higher than the time-averaged CR flux from all sources, if a nearby GRB occurred recently. If such a source is present, its narrow spectrum may produce a gap in the total spectrum. These signatures should be detectable by the planned Auger CR experiment.