Suchergebnisse

Please read abstract in the article. ; DATA AVAILABILITY: The data underlying this article were accessed from the South African Radio Astronomy Observatory (SARAO; www.ska.ac.za). ; The National Research Foundation (NRF), SARAO. MP, SMR, the UK Science and Technology Facilities Council, the Oxford Hintze Centre for Astrophysical Surveys that is funded through generous support from the Hintze Family Charitable Foundation, the Rhodes University Centre for Radio Astronomy Techniques and Technologies (RATT), the European Union's Horizon 2020 research and innovation program under a Marie Skłodowska-Curie grant, the Inter-University Institute for Data Intensive Astronomy (IDIA), the South African Research Chairs Initiative of the NRF, the Glasstone Foundation, the Italian Ministry of Foreign Affairs and International Cooperation, the Science and Technology Foundation (FCT, Portugal), the Science and Technology Facilities Council (STFC), the South African Astronomical Observatory, the Bundesministerium für Bildung und Forschung (BMBF), the Inter-University Institute for Data Intensive Astronomy (IDIA) and the ERC-Stg DRANOEL. ; https://academic.oup.com/mnras ; hj2022 ; Physics

Measuring radio emission from air showers offers a novel way to determine properties of the primary cosmic rays such as their mass and energy. Theory predicts that relativistic time compression effects lead to a ring of amplified emission which starts to dominate the emission pattern for frequencies above ~100 MHz. In this article we present the first detailed measurements of this structure. Ring structures in the radio emission of air showers are measured with the LOFAR radio telescope in the frequency range of 110 - 190 MHz. These data are well described by CoREAS simulations. They clearly confirm the importance of including the index of refraction of air as a function of height. Furthermore, the presence of the Cherenkov ring offers the possibility for a geometrical measurement of the depth of shower maximum, which in turn depends on the mass of the primary particle. ; We acknowledge financial support from the Netherlands Research School for Astronomy (NOVA), the Samenwerkingsverband Noord-Nederland (SNN), the Foundation for Fundamental Research on Matter (FOM) and the Netherlands Organization for Scientific Research (NWO), VENI Grant 639-041-130. We acknowledge funding from an Advanced Grant of the European Research Council under the European Union's Seventh Framework Program (FP/2007-2013)/ERC Grant Agreement no. 227610.

Measuring radio emission from air showers offers a novel way to determine properties of the primary cosmic rays such as their mass and energy. Theory predicts that relativistic time compression effects lead to a ring of amplified emission which starts to dominate the emission pattern for frequencies above ~100 MHz. In this article we present the first detailed measurements of this structure. Ring structures in the radio emission of air showers are measured with the LOFAR radio telescope in the frequency range of 110 - 190 MHz. These data are well described by CoREAS simulations. They clearly confirm the importance of including the index of refraction of air as a function of height. Furthermore, the presence of the Cherenkov ring offers the possibility for a geometrical measurement of the depth of shower maximum, which in turn depends on the mass of the primary particle. ; We acknowledge financial support from the Netherlands Research School for Astronomy (NOVA), the Samenwerkingsverband Noord-Nederland (SNN), the Foundation for Fundamental Research on Matter (FOM) and the Netherlands Organization for Scientific Research (NWO), VENI Grant 639-041-130. We acknowledge funding from an Advanced Grant of the European Research Council under the European Union's Seventh Framework Program (FP/2007-2013)/ERC Grant Agreement no. 227610.