Andreas Horneffer

for the LOPES Collaboration

Results from LOPES,an Overview

Radboud University Nijmegen

Radboud University Nijmegen

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

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 LOPESSTAR 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

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°.

Radboud University Nijmegen

Radio Pulse Height Parametrisation

Comparison with KASCADE data

leads to parameterization formula:

εEW=A·(B-cos(α))·cos(θ)·exp(R/R0)

·(E/1017eV)γ [μV/m MHz]

With: A=11±1 B=1.16±0.025

R0=236 ±81 γ=0.95±0.04

E

Horneffer et al. (LOPES coll.) ICRC(2007) Merida

Radboud University Nijmegen

Lateral Behavior

Investigate the lateral behavior by: Statistical analysis of many

events Analysis of single antennas in

strong events

R0=236 ±81

single event110 events

Radboud University Nijmegen

Lateral BehaviorFlat Events & Simulations

S. Nehls, PhD-Thesis 2008 Uni Karlsruhe

Simulations predict systematically smaller scale parameters R0,sim<100m

Some events show a “flat” behavior with large R0 no flat distributions obtained in simulations

Radboud University Nijmegen

Lateral BehaviorFlat Events & Simulations

Possible explanation: flat inner region Needs further study!

S. Nehls, PhD-Thesis 2008 Uni Karlsruhe

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

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

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

Radboud University Nijmegen

Preparing the Future

LOFAR: High sensitivity Excellent calibration

Radio@Auger Development of

autonomous antennas Self triggering

Simulations!!!

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/R0)

Larger R0 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.

Radboud University Nijmegen

ASTRON, The NetherlandsH. Butcher G. de BruynC.M. de Vos G.W. KantY. Koopman H.J. PeppingG. Schoonderbeek W. van CapellenS. Wijnholds

Max-Planck-Institut für Radio-astronomie, Bonn, GermanyP.L. Biermann J.A. Zensus

National Inst of Physics and Nuclear Engineering Bucharest,RomaniaI.M. Brancus B. MitricaM. Petcu A. SaftoiuO. Sima G. Toma

Istituto di Fisica dello Spazio Interplanetario, Torino, ItalyE. Cantoni P.L. GhiaC. Morello G.C. Trinchero

IPE, FZK, GermanyT. Asch H. Gemmeke O. Krömer M. ManewaldL. Petzold A. Schmidt

Dept of Astrophysics, Nijmegen, The NetherlandsL. Bähren S. Buitink H. Falcke J.R. Hörandel A. Horneffer J. KuijpersS. Lafèbre A. NiglJ. Petrovic K. Singh

Soltan Institute for Nuclear Studies, Lodz, PolandP. Łuczak J. Zabierowski

Universität Siegen, GermanyM. Brüggemann P. BuchholzC. Grupen D. KickelbickY. Kolotaev S. OverW. Walkowiak

Univ Wuppertal, GermanyJ. Auffenberg D. FuhrmannR. Glasstetter K.H. KampertJ. Rautenberg

Institut für Kernphysik, FZK, GermanyW.D. Apel J.C. ArteagaA.F. Badea K. BekkJ. Blümer H. BozdogK. Daumiller P. DollR. Engel M. FingerA. Haungs D. HeckT. Huege P.G. IsarH.J. Mathes H.J. MayerS. Nehls J. OehlschlägerT. Pierog H. RebelM. Roth H. SchielerF. Schröder H. UlrichA. Weindl J. WocheleM. Wommer

Dipartimento di Fisica Generale dell'Universita, Torino, ItalyM. Bertaina A. ChiavassaF. Di Pierro G. Navarra

Univ Karlsruhe, GermanyF. Cossavella V. De SouzaM. Ender D. KangK. Link M. LudwigM. Melissas N. Palmieri

LOPES Collaboration

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

~ averagebeamsize

Interferometry gives excellent

position information!

The radio emission from

normal showers is

directly associated with the particle

shower within our beamsize.

Radboud University Nijmegen

Simulations:Extraction of Xmax

Lafebre et al. (2008), in prep.

Huege et al. (2008)