The cosmic ray—X-ray connection: Effects of nonlinear shock acceleration on photon production in SNRs

X-ray observations over the past several years have led to the discovery of nonthermal X-ray emission arising in the shells of many young supernova remnants, including SN 1006, Cas A, and Tycho. This emission is thought to be synchrotron emission from electrons that have been shock accelerated to hundreds of TeV, and thus represents strong evidence that cosmic rays are accelerated in SNR shocks. The X-ray observations are corroborated by detection of TeV gamma rays from two of these remnants. A systematic investigation of young, shell-like remnants suggests that the nonthermal X-ray emission from shock-accelerated electrons is a common, if not ubiquitous, feature. We review the status of the X-ray observations and describe how they can be used to provide insight into the shock acceleration process.

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Morphology of radio relics – I. What causes the substructure of synchrotron emission?

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3018 ◽

2020 ◽

Vol 500 (1) ◽

pp. 795-816

Author(s):

P Domínguez-Fernández ◽

M Brüggen ◽

F Vazza ◽

W E Banda-Barragán ◽

K Rajpurohit ◽

...

Keyword(s):

Magnetic Field ◽

Mach Number ◽

Three Dimensional ◽

Cosmic Ray ◽

Shock Acceleration ◽

Synchrotron Emission ◽

Diffusive Shock Acceleration ◽

X Ray ◽

Set Up ◽

Index Maps

ABSTRACT High-resolution radio observations of cluster radio relics often show complex spatial and spectral features. However, it is not clear what these features reveal about the underlying magnetic field properties. We performed three-dimensional magnetohydrodynamical simulations of merger shock waves propagating through a magnetized, turbulent intracluster medium. Our model includes the diffusive shock acceleration (DSA) of cosmic ray electrons, their spatial advection and energy losses at run-time. With this set-up we can investigate the relation between radio substructure and pre-shock plasma conditions in the host cluster. We find that upstream turbulence plays a major role in shaping the properties of radio relics produced downstream. Within the assumption of DSA, we can reproduce the observed discrepancy between the X-ray derived Mach number of shocks, and the Mach number inferred from radio spectra. Our simulated spectral index maps and profiles across the radio relic also suggest that the standard deviation of the upstream magnetic field must be relatively small ($\sigma _B\le 1 \, \mu$G) in order to reproduce observations and therefore radio relics can potentially constrain the distribution of magnetic fields in galaxy clusters outskirts.

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X-ray Synchrotron Polarization from Turbulent Plasmas in Supernova Remnants

Proceedings of the International Astronomical Union ◽

10.1017/s174392131700480x ◽

2017 ◽

Vol 12 (S331) ◽

pp. 242-247

Author(s):

Matthew G. Baring

Keyword(s):

Supernova Remnants ◽

Active Regions ◽

Cosmic Ray ◽

Polarization Degree ◽

Shock Acceleration ◽

Field Energy ◽

X Rays ◽

Mhd Turbulence ◽

X Ray ◽

Turbulent Field

AbstractAs supernova remnants (SNRs) age, they become efficient cosmic ray accelerators at their outer shell shocks. The current paradigm for shock acceleration theory favors turbulent field environs in the proximity of these shocks, turbulence driven by current instabilities involving energetic ions. With the imminent prospect of dedicated X-ray polarimeters becoming a reality, the possibility looms of probing turbulence on scales that couple to the super-TeV electrons that emit X-rays. This paper presents model X-ray polarization signatures from energetic electrons moving in simulated MHD turbulence of varying levels of “chaos.” The emission volumes are finite slabs that represent the active regions of young SNR shells. We find that the turbulent field energy must be quite limited relative to that of the total field in order for the X-ray polarization degree to be as strong as the radio measures obtained in some remnants. Results presented are pertinent to the planned IXPE and XIPE polarimeters.

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Effects of the solar wind termination shock and heliosheath on theheliospheric modulation of galactic and anomalous Helium

Annales Geophysicae ◽

10.5194/angeo-22-3063-2004 ◽

2004 ◽

Vol 22 (8) ◽

pp. 3063-3072 ◽

Cited By ~ 15

Author(s):

U. W. Langner ◽

M. S. Potgieter

Keyword(s):

Solar Wind ◽

Cosmic Ray ◽

Magnetic Polarity ◽

Termination Shock ◽

Shock Acceleration ◽

Diffusive Shock Acceleration ◽

Cosmic Ray Modulation ◽

Low Energies ◽

Solar Wind Termination Shock ◽

Charge Sign

Abstract. The interest in the role of the solar wind termination shock and heliosheath in cosmic ray modulation studies has increased significantly as the Voyager 1 and 2 spacecraft approach the estimated position of the solar wind termination shock. The effect of the solar wind termination shock on charge-sign dependent modulation, as is experienced by galactic cosmic ray Helium (He++) and anomalous Helium (He+), is the main topic of this work, and is complementary to the previous work on protons, anti-protons, electrons, and positrons. The modulation of galactic and anomalous Helium is studied with a numerical model including a more fundamental and comprehensive set of diffusion coefficients, a solar wind termination shock with diffusive shock acceleration, a heliosheath and particle drifts. The model allows a comparison of modulation with and without a solar wind termination shock and is applicable to a number of cosmic ray species during both magnetic polarity cycles of the Sun. The modulation of Helium, including an anomalous component, is also done to establish charge-sign dependence at low energies. We found that the heliosheath is important for cosmic ray modulation and that its effect on modulation is very similar for protons and Helium. The local Helium interstellar spectrum may not be known at energies

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Effect of cosmic ray/X-ray ionization on supermassive black hole formation

Monthly Notices of the Royal Astronomical Society ◽

10.1111/j.1365-2966.2011.19229.x ◽

2011 ◽

Vol 416 (4) ◽

pp. 2748-2759 ◽

Cited By ~ 38

Author(s):

Kohei Inayoshi ◽

Kazuyuki Omukai

Keyword(s):

Black Hole ◽

Cosmic Ray ◽

Hole Formation ◽

X Ray ◽

Black Hole Formation ◽

Supermassive Black Hole

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Radio and X-ray connection in radio mini-halos: Implications for hadronic models

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937207 ◽

2020 ◽

Vol 640 ◽

pp. A37 ◽

Cited By ~ 2

Author(s):

A. Ignesti ◽

G. Brunetti ◽

M. Gitti ◽

S. Giacintucci

Keyword(s):

Magnetic Field ◽

Large Fraction ◽

Cosmic Ray ◽

Physical Parameters ◽

Model Parameters ◽

Relativistic Electrons ◽

X Rays ◽

X Ray ◽

Hadronic Model ◽

Radio Halos

Context. A large fraction of cool-core clusters are known to host diffuse, steep-spectrum radio sources, called radio mini-halos, in their cores. Mini-halos reveal the presence of relativistic particles on scales of hundreds of kiloparsecs, beyond the scales directly influenced by the central active galactic nucleus (AGN), but the nature of the mechanism that produces such a population of radio-emitting, relativistic electrons is still debated. It is also unclear to what extent the AGN plays a role in the formation of mini-halos by providing the seeds of the relativistic population. Aims. In this work we explore the connection between thermal and non-thermal components of the intra-cluster medium in a sample of radio mini-halos and we study the implications within the framework of a hadronic model for the origin of the emitting electrons. Methods. For the first time, we studied the thermal and non-thermal connection by carrying out a point-to-point comparison of the radio and the X-ray surface brightness in a sample of radio mini-halos. We extended the method generally applied to giant radio halos by considering the effects of a grid randomly generated through a Monte Carlo chain. Then we used the radio and X-ray correlation to constrain the physical parameters of a hadronic model and we compared the model predictions with current observations. Results. Contrary to what is generally reported in the literature for giant radio halos, we find that the mini-halos in our sample have super-linear scaling between radio and X-rays, which suggests a peaked distribution of relativistic electrons and magnetic field. We explore the consequences of our findings on models of mini-halos. We use the four mini-halos in the sample that have a roundish brightness distribution to constrain model parameters in the case of a hadronic origin of the mini-halos. Specifically, we focus on a model where cosmic rays are injected by the central AGN and they generate secondaries in the intra-cluster medium, and we assume that the role of turbulent re-acceleration is negligible. This simple model allows us to constrain the AGN cosmic ray luminosity in the range ∼1044−46 erg s−1 and the central magnetic field in the range 10–40 μG. The resulting γ-ray fluxes calculated assuming these model parameters do not violate the upper limits on γ-ray diffuse emission set by the Fermi-LAT telescope. Further studies are now required to explore the consistency of these large magnetic fields with Faraday rotation studies and to study the interplay between the secondary electrons and the intra-cluster medium turbulence.

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X-ray Dips in AGN and Microquasars – Collapse Timescales of Inner Accretion Disc

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3838 ◽

2020 ◽

Author(s):

Mayur B Shende ◽

Prashali Chauhan ◽

Prasad Subramanian

Keyword(s):

Collisionless Plasma ◽

Cosmic Ray ◽

Outer Radius ◽

Accretion Disc ◽

Accretion Discs ◽

X Rays ◽

Temporal Behaviour ◽

X Ray ◽

Ray Diffusion ◽

3C 120

Abstract The temporal behaviour of X-rays from some AGN and microquasars is thought to arise from the rapid collapse of the hot, inner parts of their accretion discs. The collapse can occur over the radial infall timescale of the inner accretion disc. However, estimates of this timescale are hindered by a lack of knowledge of the operative viscosity in the collisionless plasma comprising the inner disc. We use published simulation results for cosmic ray diffusion through turbulent magnetic fields to arrive at a viscosity prescription appropriate to hot accretion discs. We construct simplified disc models using this viscosity prescription and estimate disc collapse timescales for 3C 120, 3C 111, and GRS 1915+105. The Shakura-Sunyaev α parameter resulting from our model ranges from 0.02 to 0.08. Our inner disc collapse timescale estimates agree well with those of the observed X-ray dips. We find that the collapse timescale is most sensitive to the outer radius of the hot accretion disc.

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Nonthermal Processes in Large Solar Flares

Symposium - International Astronomical Union ◽

10.1017/s0074180900071862 ◽

1975 ◽

Vol 68 ◽

pp. 425-426

Author(s):

H. S. Hudson ◽

T. W. Jones ◽

R. P. Lin

Keyword(s):

Shock Wave ◽

Solar Flares ◽

Interplanetary Medium ◽

Interplanetary Shock ◽

Energy Output ◽

Shock Acceleration ◽

List Type ◽

Lower Corona ◽

X Ray ◽

Interplanetary Shock Wave

SummaryIn many small solar flares the ∼10–100 keV electrons accelerated during the flash phase contain the bulk of the total flare energy output. In large flares, such as those in the period 1972, August 2–7, the flash phase electrons are present in substantially greater numbers. These electrons can explosively heat the chromosphere-lower corona and eject flare material. The ejected matter can produce a shock wave which will then accelerate nucleons and electrons to relativistic energies. We analyze energetic particle, radio, X-ray, gamma ray and interplanetary shock observations of the 1972 August flares to obtain quantitative estimates of the energy contained in each facet of these large flares. In general these observations are consistent with the above hypothesis. In particular: (1)From the X-ray emission (van Beek et al., 1973) the energy contained in >25 keV electrons is calculated to be 2 × 1032 erg for the 1972, August 4 event. Since the lower energy cutoff to the electron spectrum is known to be below 25 keV and possibly below 10 keV, the electrons contain enough energy to produce the following interplanetary shock wave, which has by far the bulk of the energy dissipated in the flare. Similar numbers are obtained for the large August 7 flare event.(2)From the γ-ray emission (Chupp et al., 1973) the energy in protons dumped at the same level of the atmosphere, assuming a thick target situation, is at least a factor of three smaller than the electrons. Moreover the γ-ray emission indicates that the bulk of the protons are accelerated at least several minutes after the electrons. Thus it is more likely that the electrons are responsible for the flare optical (Hα and white light) emissions which occur in the chromosphere.(3)Approximately 5% of the electrons and 99% of the protons escape into the interplanetary medium to be observed by spacecraft. This situation is consistent with the hypothesis of shock acceleration of the protons high in the solar corona.(4)The four most intense X-ray bursts observed during the period July 31–August 11 are the only bursts followed by an interplanetary shock wave and a new injection of energetic protons into the interplanetary medium.

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