This theme includes the three following topics: cosmic rays, intergalactic magnetic fields and multimessenger astrophysics based on high-energy neutrinos and gamma-rays.
Cosmic rays
Despite cosmic rays was discovered more then 100 years ago, their origin is still unknown. We suggested that local 2 Myr Super Nova can explain number of anomalies in cosmic ray data. Same Super Nova can be a reason of climate and life diversity change on Earth in the past. In our group developed theory of galactic and extragalactic cosmic ray propagation. We discovered new type of cosmic ray diffusion around their sources. We developed theory of anisotropic cosmic ray diffusion in galaxy.
Signatures of a two million year old supernova in the spectra of cosmic ray protons, antiprotons and positrons M.Kachelriess, A.Neronov and D.Semikoz Phys.Rev.Lett. 115 (2015) 18, 181103
Cosmic Ray Models M.Kachelriess and D.Semikoz Prog.Part.Nucl.Phys. 109 (2019) 103710
Team: D.Semikoz (DR CNRS), A.Neronov (Prof. U. Paris), M.Bouyahiaoui (PhD student 2018-2021)
Intergalactic magnetic fields
The noise excess recently discovered by several Pulsar Timing Arrays experiments can be explained in terms of a stochastic gravitational-wave background due to a primordial magnetic field at the QCD scale.
The Intergalactic Magnetic Field (IMF) in the voids of large scale structure is dominated by the contribution of primordial magnetic fields, possibly created during inflation or at phase transitions in the Early Universe. Primordial magnetic fields can be probed via measurements of secondary gamma-ray emission from gamma-ray interactions with extragalactic background light. Lower bounds on the magnetic field in the voids were derived from the non-detection of this emission.
NANOGrav signal from magnetohydrodynamic turbulence at the QCD phase transition in the early Universe Andrii Neronov, Chiara Caprini, A.Roper Pol and D.Semikoz Phys.Rev.D 103 (2021) L041302
Team: D.Semikoz (DR CNRS), A. Neronov (Prof. U.Paris), M. Ramsoy (postdoc 2020-2022), A.Roper Pol (postdoc 2020-2022), A.Korochkin (PhD student 2018-2022)
Multimessenger astrophysics
Despite their discovery about 10 years ago, sources of astrophysical neutrinos are still unknown. We worked on multimessenger astrophysics which neutrinos and gamma-rays at energies above TeV. In particular we constructed models of galactic and extralactic neutrino sources and compared their predictions with gamma-ray and neutrino observations.
Multimessenger gamma-ray counterpart of the IceCube neutrino signal M.Kachelriess, A.Neronov and D.Semikoz Phys.Rev.D 98 (2018) 2, 023004
Hot spots in the neutrino flux created by cosmic rays from Cygnus and Vela
M.Bouyahiaoui, M.Kachelriess and D.Semikoz Phys.Rev.D 106 (2022) 6, 6
Team: A. Neronov, D. Semikoz , M.Bouyahiaoui (PhD student 2018-2021)