1. Andreas Horneffer for the LOPES Collaboration Results from LOPES, an Overview Radboud University Nijmegen

2. Radio Emission from Air Showers Air showers emit short, intense radio pulses Radiation due to geomagnetic emission process e.g. geosynchrotron Coherent emission at low frequencies Measuring the radio emission from air showers could give several benefits: Higher duty cycle than fluorescence telescopes Effective RFI suppression allows measuring in polluted (populated) areas Data integrated over the shower evolution, can be complementary to particle detectors High angular resolution possible

3. Radboud University Nijmegen LOPES (LOFAR Prototype Station) Set up at and working together with KASCADE-Grande Frequency range of 40 – 80 MHz Triggered by KASCADE or Grande large event trigger  10 antennas in the first phase  30 antennas in second phase  reconfigured for dual-polarization plus LOPES STAR antennas Goals: Develop techniques to measure the radio emission from air showers Determine the radiation mechanism of air showers Measure the properties of the radio emission from air showers Calibrate the radio data with theoretical and experimental values from an existing air shower array

4. Radboud University Nijmegen First detection of CR radio pulse by LOPES Falcke et al. (LOPES collaboration) 2005, Nature, 435, 313 Strong coherent radio pulse coincident with air shower Shows direct association of radio with air shower geometry All-sky radio-only mapping Imaging (AZ-EL) with time resolution of 12.5 ns Total duration is ~200 ns No cleaning was performed, side lobes still visible Location of burst agrees with KASCADE location to within 0.5°.

5. Radboud University Nijmegen Radio Pulse Height Parametrisation Comparison with KASCADE data leads to parameterization formula: ε EW =A·(B-cos(α))·cos(θ)·exp(R/R 0 ) ·(E/10 17 eV) γ [μV/m MHz] With: A=11±1 B=1.16±0.025 R 0 =236 ±81 γ=0.95±0.04 E Horneffer et al. (LOPES coll.) ICRC(2007) Merida

6. Radboud University Nijmegen Lateral Behavior Investigate the lateral behavior by: Statistical analysis of many events Analysis of single antennas in strong events R 0 =236 ±81 single event 110 events

7. Radboud University Nijmegen Lateral Behavior Flat Events & Simulations S. Nehls, PhD-Thesis 2008 Uni Karlsruhe Simulations predict systematically smaller scale parameters R 0,sim <100m Some events show a “flat” behavior with large R 0 no flat distributions obtained in simulations

8. Radboud University Nijmegen Lateral Behavior Flat Events & Simulations Possible explanation: flat inner region Needs further study! S. Nehls, PhD-Thesis 2008 Uni Karlsruhe

9. Radboud University Nijmegen Frequency Spectrum Spectrum of the radio pulse from two methods: sub-band filtering Fourier-transform of single pulses Can be fit with a power law of slope: -1 No dependence on direction, energy or distance found Consistent with simulations Nigl et al. (LOPES coll.) A&A accepted power law slope: α=-1±0.3

10. Radboud University Nijmegen Thunderstorm Effects Measured clear radio excess during thunderstorms For E>100 V/cm E-field force dominates B-field: Fair weather: E=1 V/cm Thunderstorms: E=1 kV/cm Electric fields have two main effects depending on geometry: Additional curvature of e ± Linear acceleration of e ±  B-field effect dominates under normal conditions  >90% duty cycle possible Buitink et al. (LOPES coll.) A&A 467(2007)385 Thunderstorm events control sample ‘perfect weather’ sample

11. Radboud University Nijmegen Polarization Some events show strong polarization In general: Events from East or West have stronger NS component Events from North or South have stronger EW component EW Component NS Component Isar et al. (LOPES coll.) ICRC(2007) Merida

12. Radboud University Nijmegen Preparing the Future LOFAR: High sensitivity Excellent calibration Radio@Auger Development of autonomous antennas Self triggering Simulations!!!

13. Radboud University Nijmegen Summary Radio signal depends on angle to geomagnetic field. Confirmation of geomagnetic emission process. Pulse height scales about linearly with primary energy. Confirmation of coherent emission. Pulse height scales with distance: ε~exp(R/R 0 ) Larger R 0 value found than in simulations, flattening at the center? Frequency spectrum is a decreasing power law or exponential. Compatible with simulations Amplified radio signal during thunderstorms. Strong electric fields can influence the emission process. Polarization shows azimuthal dependence. Similar to simulations. Not shown: LOPES is more sensitive to inclined air showers than KASCADE. The angular resolution of LOPES increases with primary energy.

14. Radboud University Nijmegen ASTRON, The Netherlands H. ButcherG. de Bruyn C.M. de VosG.W. Kant Y. KoopmanH.J. Pepping G. SchoonderbeekW. van Capellen S. Wijnholds Max-Planck-Institut für Radio- astronomie, Bonn, Germany P.L. BiermannJ.A. Zensus National Inst of Physics and Nuclear Engineering Bucharest,Romania I.M. BrancusB. Mitrica M. PetcuA. Saftoiu O. SimaG. Toma Istituto di Fisica dello Spazio Interplanetario, Torino, Italy E. CantoniP.L. Ghia C. MorelloG.C. Trinchero IPE, FZK, Germany T. AschH. Gemmeke O. KrömerM. Manewald L. PetzoldA. Schmidt Dept of Astrophysics, Nijmegen, The Netherlands L. Bähren S. Buitink H. FalckeJ.R. Hörandel A. HornefferJ. Kuijpers S. LafèbreA. Nigl J. PetrovicK. Singh Soltan Institute for Nuclear Studies, Lodz, Poland P. ŁuczakJ. Zabierowski Universität Siegen, Germany M. BrüggemannP. Buchholz C. GrupenD. Kickelbick Y. KolotaevS. Over W. Walkowiak Univ Wuppertal, Germany J. AuffenbergD. Fuhrmann R. GlasstetterK.H. Kampert J. Rautenberg Institut für Kernphysik, FZK, Germany W.D. ApelJ.C. Arteaga A.F. BadeaK. Bekk J. BlümerH. Bozdog K. Daumiller P. Doll R. EngelM. Finger A. HaungsD. Heck T. HuegeP.G. Isar H.J. MathesH.J. Mayer S. NehlsJ. Oehlschläger T. PierogH. Rebel M. RothH. Schieler F. SchröderH. Ulrich A. WeindlJ. Wochele M. Wommer Dipartimento di Fisica Generale dell'Universita, Torino, Italy M. BertainaA. Chiavassa F. Di PierroG. Navarra Univ Karlsruhe, Germany F. Cossavella V. De Souza M. EnderD. Kang K. LinkM. Ludwig M. Melissas N. Palmieri LOPES Collaboration

15. Radboud University Nijmegen Positional Accuracy linear improvement with SNR Air showers are amplified and modified in thunderstorm electric field! Nigl 2007, PhD, RU Nijmegen Particle Detectors vs. Radio Antennas ~ average beamsize Interferometry gives excellent position information! The radio emission from normal showers is directly associated with the particle shower within our beamsize.

16. Radboud University Nijmegen Simulations: Extraction of X max Lafebre et al. (2008), in prep. Huege et al. (2008)