Stavros Dimitrakoudis

Stavros Dimitrakoudis
University of Alberta | UAlberta · Department of Physics

PhD

About

43
Publications
3,283
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1,020
Citations
Citations since 2016
15 Research Items
920 Citations
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2016201720182019202020212022050100150200
Introduction
Stavros Dimitrakoudis currently works at the Department of Physics, University of Alberta. Stavros does research in Space Physics and Astrophysics. Their most recent publication is 'A Multimessenger Picture of the Flaring Blazar TXS 0506+056: implications for High-Energy Neutrino Emission and Cosmic Ray Acceleration'.
Additional affiliations
February 2014 - May 2015
National Observatory of Athens
Position
  • PostDoc Position

Publications

Publications (43)
Article
Full-text available
Using ground magnetometer measurements from the IMAGE array over the timespan of one solar cycle, we apply wavelets to statistically assess the power of ultra‐low frequency (ULF) waves from L = 3.34 to L = 13.6 as a function of Kp, solar wind speed (Vsw ${V}_{\text{sw}}$), solar wind dynamic pressure (Pdyn ${P}_{\text{dyn}}$), Dst, and Bz ${B}_{z}$...
Article
Full-text available
Geomagnetically induced currents (GICs) can be driven in terrestrial electrical power grids as a result of the induced electric fields arising from geomagnetic disturbances (GMD) resulting from the dynamics of the coupled magnetosphere‐ionosphere‐ground system. However, a key issue is to assess an optimum spacing for the magnetometer stations in or...
Preprint
Full-text available
Blazar hadronic models have been developed in the past decades as an alternative to leptonic ones. In hadronic models the gamma-ray emission is associated with synchrotron emission by protons, and/or secondary leptons produced in proton-photon interactions. Together with photons, hadronic emission models predict the emission of neutrinos that are t...
Preprint
Blazars have been proposed as efficient particle accelerators and promising neutrino sources long before the discovery of astrophysical high-energy neutrinos. The recent report by the IceCube Collaboration of a $\sim 3.5\sigma$ excess of $13\pm5$ neutrino events in the direction of the blazar TXS 0506+056 during a six month-long period in 2014-2015...
Preprint
Full-text available
Active galactic nuclei (AGN) with relativistic jets, powered by gas accretion onto their central supermassive black hole (SMBH), are unique laboratories for studying the physics of matter and elementary particles in extreme conditions that cannot be realized on Earth. For a long time since the discovery of AGN, photons were the only way to probe th...
Article
Detection of the IceCube-170922A neutrino coincident with the flaring blazar TXS 0506+056, the first and only ~3σ high-energy neutrino source association to date, offers a potential breakthrough in our understanding of high-energy cosmic particles and blazar physics. We present a comprehensive analysis of TXS 0506+056 during its flaring state, usin...
Preprint
Full-text available
Detection of the IceCube-170922A neutrino coincident with the flaring blazar TXS 0506+056, the first and only 3-sigma high-energy neutrino source association to date, offers a potential breakthrough in our understanding of high-energy cosmic particles and blazar physics. We present a comprehensive analysis of TXS 0506+056 during its flaring state,...
Article
We are pleased to address the comment on our paper from Shprits et al. since we believe it supports our conclusion that magnetopause shadowing and ultralow-frequency (ULF) wave outward transport can drive fast losses into the heart of the ultra-relativistic electron radiation belt and produce a remnant belt. As reported by Baker et al., the Septemb...
Article
Since the discovery of the Van Allen radiation belts over 50 years ago, an explanation for their complete dynamics has remained elusive. Especially challenging is understanding the recently discovered ultra-relativistic third electron radiation belt. Current theory asserts that loss in the heart of the outer belt, essential to the formation of the...
Article
Blazars, a subclass of active galactic nuclei, are prime candidate sources for the high energy neutrinos recently detected by IceCube. Being one of the brightest sources in the extragalactic X-ray and γ-ray sky as well as one of the nearest blazars to Earth, Mrk 421 is an excellent source for testing the scenario of the blazar-neutrino connection,...
Article
Full-text available
We present two ways of modeling the spectral energy distribution of blazars in the hadronic context and discuss the predictions of each "hadronic variant" on the spectral shape, the multi-wavelength variability, the cosmic-ray flux, and the high-energy neutrino emission. Focusing on the latter, we then present an application of the hadronic model t...
Article
Full-text available
We present electron phase space density (PSD) calculations as well as concurrent Pc5 and chorus wave activity observations during two intense geomagnetic storms caused by interplanetary coronal mass ejections (ICMEs) resulting in contradicting net effect. We show that, during the 17 March 2013 storm, the coincident observation of chorus and relativ...
Article
Full-text available
Ultra-low frequency (ULF) waves can contribute to the transport, acceleration and loss of electrons in the radiation belts through inward and outward diffusion. However, the most appropriate parameters to use to specify the ULF wave diffusion rates are unknown. Empirical representations of diffusion coefficients often use Kp; however, specification...
Article
Full-text available
We present a method of constraining the properties of the γ-ray emitting region in flat spectrum radio quasars in the one-zone proton synchrotron model, where the γ-rays are produced by synchrotron radiation of relativistic protons. We show that for low enough values of the Doppler factor δ, the emission from the electromagnetic (EM) cascade which...
Article
Full-text available
The recent IceCube discovery of 0.1-1 PeV neutrinos of astrophysical origin opens up a new era for high-energy astrophysics. Although there are various astrophysical candidate sources, a firm association of the detected neutrinos with one (or more) of them is still lacking. A recent analysis of plausible astrophysical counterparts within the error...
Article
Full-text available
The recent discovery of extragalactic PeV neutrinos opens a new window to the exploration of cosmic ray accelerators. The observed PeV neutrino flux is close to the Waxman–Bahcall upper bound implying that gamma-ray bursts (GRBs) may be the source of ultrahigh energy cosmic rays (UHECRs). Starting with the assumption of the GRB–UHECR connection, we...
Article
We present the neutrino and UHECR spectra obtained from a detailed fitting of the spectral energy distribution (SED) of Mrk 421 (March 2001) using two variations of the leptohadronic model. In particular, while the low-energy component (optical to X-rays) of the SED is fitted by synchrotron emission of primary electrons in both models, the high-ene...
Article
Full-text available
We explore a one-zone hadronic model that may be able to reproduce γ-ray burst (GRB) prompt emission with a minimum of free parameters. Assuming only that GRBs are efficient high-energy proton accelerators and without the presence of an ab initio photon field, we investigate the conditions under which the system becomes supercritical, i.e. there is...
Article
Full-text available
The recent discovery of extragalactic PeV neutrinos opens a new window to the exploration of cosmic-ray accelerators. The observed PeV neutrino flux is close to the Waxman-Bahcall upper bound implying that gamma-ray bursts (GRBs) may be the source of ultra-high energy cosmic rays (UHECRs). Starting with the assumption of the GRB-UHECR connection, w...
Article
Full-text available
Aims: We investigate the role of the second synchrotron self-Compton (SSC) photon generation to the multiwavelength emission from the compact regions of sources that are characterized as misaligned blazars. For this, we focus on the nearest high-energy emitting radio galaxy Centaurus A and we revisit the one-zone SSC model for its core emission. Me...
Article
Full-text available
We apply a recently developed time-dependent one-zone leptohadronic model to study the emission of the blazar Mrk 421. Both processes involving proton-photon interactions, i.e. photopair (Bethe-Heitler) and photopion, have been modeled in great detail using the results of Monte Carlo simulations, like the SOPHIA event generator, in a self-consisten...
Article
Full-text available
Aims: We investigate the role of the second synchrotron self-Compton (SSC) photon generation to the multiwavelength emission from the compact regions of sources that are characterized as misaligned blazars. For this, we focus on the nearest high-energy emitting radio galaxy Centaurus A and we revisit the one-zone SSC model for its core emission. Me...
Article
We examine the neutrino and cosmic ray spectra resulting from two models of fitting the spectral energy distribution (SED) of the blazar Mrk~421 using a self-consistent leptohadronic code. The $\gamma$-ray emission is attributed to either synchrotron radiation of ultra-high energy protons (LHs model) or to synchrotron radiation from electrons that...
Article
Τhe mechanisms behind gamma-ray bursts (GRBs) are not yet well understood. Here we investigate a model where a spectral energy distribution (SED) that looks surprisingly like a typical GRB prompt emission is generated starting with merely high energy protons and a magnetic field. Using a selfconsistent, time-dependent code we show that when the den...
Article
Full-text available
We investigate the origin of high-energy emission in blazars within the context of the leptohadronic one-zone model. We find that $\gamma$-ray emission can be attributed to synchrotron radiation either from protons or from secondary leptons produced via photohadronic processes. These possibilities imply differences not only in the spectral energy d...
Article
Full-text available
We present results on the radiative and neutrino signatures of the one-zone hadronic model. Assuming that protons are injected at a certain rate in a homogeneous spherical volume containing a magnetic field, the evolution of the system can be described by five coupled kinetic equations, for protons, electrons, photons, neutrons and neutrinos, respe...
Article
Full-text available
We present a time-dependent approach to the one-zone hadronic model in the case where the photon spectrum is produced by ultrarelativistic protons interacting with soft photons that are produced from protons and low magnetic fields. Assuming that protons are injected at a certain rate in a homogeneous spherical volume containing a magnetic field, t...
Article
Full-text available
We present some results on the radiative signatures of the one zone hadronic model. For this we have solved five spatially averaged, time-dependent coupled kinetic equations which describe the evolution of relativistic protons, electrons, photons, neutrons and neutrinos in a spherical volume containing a magnetic field. Protons are injected and los...
Article
In this work we study the energy distribution of protons and produced secondary particles which result from photomeson and Bethe-Heitler processes in interactions of soft photons with protons accelerated in a shock wave by the first order Fermi process. For this purpose we have developed a code which simulates the diffusive shock acceleration mecha...
Article
Recent observations by the H.E.S.S. collaboration of the Galactic Centre region have revealed what appears to be γ-ray emission from the decay of pions produced by interactions of recently accelerated cosmic rays with local molecular hydrogen clouds. Synthesizing a 3D hydrogen cloud map from the available data and assuming a diffusion coefficient o...
Article
Full-text available
Energy is among the characteristics of Ultra High Energy Cosmic Rays (E > 5 ×1019 eV) which could be estimated experimentally based on simulations. This paper attempts to estimate the energy of an UHECR proton by applying a Monte Carlo simulation code. A number of extensive air showers, vertical and inclined, are simulated to derive the lateral dis...
Article
Full-text available
Diffuse VHE γ radiation from the Galactic Centre ridge observed by the H.E.S.S. telescope has been convincingly linked with the propagation of recently accelerated cosmic rays that interact with molecular hydrogen clouds during their diffusion. Through a series of time-dependent simula- tions of that diffusion for different propagation parameters w...
Article
The non-linear back reaction of accelerated cosmic rays at the shock fronts, leads to the formation of a smooth precursor with a length scale corresponding to the diffusive scale of the energetic particles. Past works claimed that shocklets could be created in the precursor region of a specific shock width, which might energize few thermal particle...
Article
This The energy is among the characteristics of Ultra High Energy Cosmic Rays (E<5 x 1019 eV) which could be estimated experimentally. The following paper attempts to estimate the energy of an UHECR proton by applying a Monte Carlo simulation code. A number of vertical extensive air showers is simulated to derive the Lateral Distribution Functions...
Article
We present several ancient celestial spheres from the 8th century B.C. found throughout Greece, mainly in Thessaly, at the temple of Itonia Athena, but also in Olympia and other places. These celestial spheres have an axis, equator and several meridians and they have several markings with the symbol of stars (today's symbol for the Sun) $\odot$. Su...
Article
We present several bronze artifacts from the Archaic Age in Greece (750-480 BC) that resemble celestial spheres or forms of other astronomical significance. They are studied in the context of the Dark Age transition from Mycenaean Age astronomical themes to the philosophical and practical revival of astronomy in the Classical Age with its plethora...
Article
Full-text available
We provide a fresh analysis of the constellations in Aratos Phenomena by using the astronomical program Cybersky (by Stephen Schimpf) to check each reference of constellations within the poem for validity in 2800 BCE and 300 BCE (the later accounting for the broader period of time covering Eudoxus of Cnidus and Aratus of Soli). In each case, the la...
Article
High energy cosmic rays are most probably accelerated in astrophysical environments such as SNR and AGN jets and hotspots. In that case it is expected that the relativistic particles will interact in their acceleration sites with ambient photon fields and produce high energy electrons, gamma-rays as well as neutrinos. We present calculations from a...

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