• 16 October 2019
    DESY Award for Marcel Usner (only in German)
  • 8 October 2019
    Nobel prize 2019 in physics for theoretical discoveries in physical cosmology and for the discovery of an exoplanet orbiting a solar-type star
  • 4 September 2019
    Detection of VHE gamma-ray emission with H.E.S.S.

Understanding the multiwavelength observation of Geminga's TeV halo

The role of anisotropic diffusion of particles

Diffuse X ray emission is regulated by viewing angle and level of turbulence in the presence of a local mean magnetic field.

Uncover the mystery of the diffuse very-high-energy emission around a pulsar with anisotropic diffusion of particles

Detection of the diffuse very-high-energy gamma-ray emission within one hundred light years of the Geminga pulsar and the non-detection of the diffuse X-ray emission from the same region seem to contradict each other, because both of these two emissions arise from the same population of electrons and positrons injected from the pulsar. Hence, they are supposed to appear together given the typical properties of the interstellar medium around the pulsar. We propose that, such a puzzling result can be understood by considering the anisotropic diffusion of the injected particles. This is a natural consequence given that the coherence length of the interstellar magnetic field is on the order of a few tens parsecs as indicated by earlier observations. The model also provides a new way to probe the local interstellar magnetic field, through the flux level and the morphology of the TeV halos and their lower-energy counterparts of other pulsars. This will be fundamentally important to understand the transport of cosmic rays in our Galaxy and their origin.