Astroparticle Physics with LOPES and LOFAR Heino Falcke ASTRON, Dwingeloo, The Netherlands University of Nijmegen, The Netherlands Tim Huege, Andreas Horneffer (MPIfR Bonn) Andreas Nigl, Sven Lafèbre, Jan Kuijpers (Univ. Nijmegen) & LOPES & KASCADE Grande Collaboration Structure of Talk • Intro: Cosmic Rays • Radio Emission of CRs – Properties – Theory • LOFAR & LOPES • Neutrinos … • Conclusions Cosmic Ray Energy Spectrum • The differential Cosmic Ray spectrum is described by a steep power law with a E-2.75 decline. • Low-energy cosmic rays can be directly measured. • High-energy cosmic rays are measured through their air showers. UHECRs Power law particle distribution in astrophysical sources M87 jet spectra of bright knots Meisenheimer et al. (1997) Optical and perhaps X-ray synchrotron require TeV electrons and continuous re-acceleration in the jet! 3C273 Cosmic Ray Energy Spectrum adopted from: K. M annheim (1998) Multiplied by E2.75! The GZK-Cutoff AGASA HiRes I Randomization of charged particles • Charged particles are randomized by – the interstellar magnetic field in the Milky Way (around the knee) – the intergalactic magnetic field at the highest energies Projected view of 20 trajectories of proton primaries emanating from a point source for several energies. Trajectories are plotted until they reach a physical distance from the source of 40Mpc. • At 1020 eV one can do cosmic ray astronomy in the nearby universe. 1EeV = 1018 eV Cronin (2004) Clustering at the highest energies? Neutrons and Galactic Astronomy • Up to 1018 eV cosmic rays are predominantly Galactic. • At 1018 eV we have =109 for neutrons (mn~1 GeV) • Neutron lifetime =103sec×109=1012 sec =104.5yr • This corresponds to a travel length of 10 kpc! • Proton Larmor radius at 1018 eV is 300 pc in Galactic B-field! • Protons are isotropized – neutrons travel on straight lines. • At 1019 eV one could do Galactic Neutron-Astronomy AGASA arrival directions of CRs A (very) Brief History of Cosmic Rays Victor Hess, 1912: - discovered cosmic rays in balloon flights, through discharge of Leyden jars Pierre Auger, 1938: - Research in Giant Air Showers showed energies of primary particles above 1016 eV-- truly unimaginable for the time! • 1960’s: Cosmic rays with energies of >1019 eV detected - how are they made?? • Greisen, Zatsepin, Kuzmin (GZK): there should be a limit at ~5 X 1019 eV Shower Profiles Longitudinal - for different composition of primary - Lateral - for different secondary particles - Cosmic Rays Extensive Air Showers Detectors AUGER: 3000 km2,1600 water tanks & fluorescence Advantages of Radio Air Showers • Particle detectors on ground only measure a small fraction of electrons produced • Height of cosmic ray interaction depends on energy • Energy calibration is greatly improved by additional information (e.g., Cerenkov) • Radio could – Observe 24hrs/day – See shower maximum and possibly evolution of shower – Coherent emission reveals shape Radio measurements are usually triggered by particle detectors Radio Emission from Cosmic Ray Air Showers: History • First discovery: Jelley et al. (1965), Jodrell Bank at 44 MHz. • Theory papers by Kahn & Lerche (1968) and Colgate (1967) • Firework of activities around the world in the late 60ies & early 70ies. • In the late 70ies radio astronomy moved to higher frequencies and also CR work ceased. Jelley et al. (1965) Theory: Coherent Geosynchrotron Radiation deflection of electron-positron pairs in the earth’s magnetic field coherent emission at low frequencies emission on scales small compared to wavelength dominance of geomagnetic mechanism visible in past data highly beamed pulses of synchrotron radiation neglect Čerenkov radiation from charge excess, … equivalent to past geomagnetic approaches (Kahn & Lerche), but well-studied basis and conceptually attractive Falcke & Gorham (2003), Huege & Falcke (2003) Numerical Calculations of Geosynchrotron Calculate the electromagnetic radiation of a shower in the geomagnetic field from Maxwell’s equations: a) b) semi-analytically (Mathematica) Monte Carlo code Calculate coherence effects, spectrum, pulse form, for realistic shower geometry plus longitudinal evolution. Next steps for Monte Carlo code: E-field during severe conditions (thunderstorms) and Cherenkov process. Huege & Falcke (2004) Numerical Calculations of Geosynchrotron Most power is received at low frequencies due to coherence effects. The spectrum falls off around 50 MHz. Overall trend fits with historic account and rough levels. Absolute calibration of historic data is uncertain by a factor of 10! spectrum - R=0m - R=100 m - R=250 m Data: scaled Spencer ‘69 & Prah 1971 (Haverah Park). Huege & Falcke (2003) (semi-analytic solution) Numerical Calculations of Geosynchrotron Due to relativistic motion the emission is highly beamed in the forward direction. The emission falls off radially and is broader for smaller frequencies. The foot print is several hundred meters. Higher energy cosmic rays can be seen up to km. radial dependence Huege & Falcke (2003) (semi-analytic solution) Numerical Calculations of Geosynchrotron Surprisingly, the emission is largely isotropic in azimuth. The footprint becomes more elongated and bigger for inclined showers. New insight: Due to this effect and the very low attenuation of radio, inclined showers should be ideal for radio detections! inclination dependence Huege & Falcke (2005) (Monte Carlo) LOFAR • interferometer for the frequency range of 10 - 200 MHz • array of 100 stations of 100 dipole antennas • baselines of 10m to 400 km • fully digital: received waves are digitized and sent to a central computer cluster • Ideal for observing transient events LOFAR Cosmic Ray Performance • The full LOFAR array will measure CRs from 2·1014 eV to 1020 eV with baselines varying from 1 m to 300 km unique • LOFAR will be an ideal multipurpose air shower detector (almost) „for free“ – if we know how to use it • Needs: Combination with particle counters for calibration somewhere. highly competitive giant air shower array in the north! LOFAR Full Array LOFAR densely packed array Galactic Pole Falcke & Gorham (2003) LOPES Partners • MPIfR Bonn – Project design and development • Univ. Nijmegen – data center, theory & software • Uni/FZ Karlsruhe & KASCADE Grande collab. – air shower array & site, on-site support • ASTRON (Dwingeloo) – antennas, basic electronic design • BMBF (Ministry of Science) – Funding within the new ”Verbundforschung Astroteilchenphysik” Cosmics @ Univ of Nijmegen • L3 Cosmics • NAHSA (CR detectors on schools) • LOPES/LOFAR – – – – – FOM grant + ASTRON grant 2 PhD students, 1 Postdoc (tbd) 2 faculty Data center for LOPES (multi-TB RAID server) Will be lead institute for LOFAR cosmics KASCADE • The KASCADE experiment is situated on the site of Forschungszentrum Karlsruhe in Germany. • It measures simultaneously the electromagnetic, muonic and hadronic components of extensive air showers. • The goal of KASCADE is the determination of the chemical composition of primary particles of cosmic rays around and above the "knee„ (1015-1016 eV) KASCADE • The KASCADE experiment is situated on the site of Forschungszentrum Karlsruhe in Germany. • It measures simultaneously the electromagnetic, muonic and hadronic components of extensive air showers. • The goal of KASCADE is the determination of the chemical composition of primary particles of cosmic rays around and above the “knee” (1015-1016 eV) KASCADE-Grande The red dots show the location of new particle detectors: expansion of KASCADE to KASCADE Grande LOPES: Current Status 10 antenna prototype at KASCADE (all 10 antennas running) triggered by a large event trigger (10 out of 16 array clusters) offline correlation of KASCADE & LOPES events (not integrated yet into the KASCADE DAQ) KASCADE can provide starting points for LOPES air shower reconstruction core position of the air shower direction of the air shower size of the air shower Hardware of LOPES10 LOPES-Antenna Solar Burst Oct. 28 All-Sky Dirty Map (AzEl) Solar Burst Integration: 1 ms Frequency: 45-75 MHz Bandwidth: 30 MHz Antennas: 8 Resolution: ~3° Location: Karlsruhe (research center) Correlation, Imaging, and Cleaning with aips++ dirty map simulated map Solar Burst Integration: 1 ms Frequency: 45-75 MHz Bandwidth: 30 MHz Antennas: 8 cleaned map Resolution: ~3° Location: Karlsruhe (research center) circular beam Digital Filtering raw data from one antenna Digital Filtering power spectrum before and after filtering Digital Filtering time series after filtering Digital Filtering time series after filtering Bright Event Layout Bright Event E-Field Bright Event Power Bright Event Power after Beamforming Bright Event E-Field after Beamforming Bright Event Beamformed Power Bright Event Movie All-sky map (AZ-EL) Mapping with a timeresolution of 12.5 ns Interpolation of sub-frames Total duration is ~200 ns No cleaning was performed (would require new software: clean in time and space) Location of burst agrees with KASCADE location to within 0.5°. Neutrino-induced air showers • At 1019 eV, horizontal neutrinos have 0.2% chance of producing a shower along a ~250 km track, 0.5% at 1020 eV • Could be distinguished from distant cosmic ray interactions by radio wavefront curvature: neutrinos interact all along their track with equal probability, thus are statistically closer & deeper in atmosphere • • • Example of tau neutrino interactions: resulting tau lepton decay produces large swath of particles, out to 50km Left: ground particle density from electron decay channel. Right: from pion decay channel Results from studies for Auger air shower array, Bertou et al. 2001, astroph/0104452 stolen from P. Gorham Lunar Regolith Interactions & RF Cherenkov radiation • At ~100 EeV energies, neutrino interaction length in lunar material is ~60km • Rmoon ~ 1740 km, so most detectable interactions are grazing rays, but detection not limited to just limb • Refraction of Cherenkov cone at regolith surface “fills in” the pattern, so acceptance solid angle is ~50 times larger than apparent solid angle of moon • GLUE-type experiments have huge effective volume can set useful limits in short time • Large VHF array may have lower energy threshold, also higher duty cycle if phasing allows multiple source tracking Gorham et al. (2000) Radio from Neutrinos in Ice ANtarctic Impulsive Transient Antenna M. Rosen, Univ. of Hawaii Solar Panels ANITA Gondola & Payload Antenna array Cover (partially cut away) 600 km radius, 1.1 million km2 • NASA funding started 2003 • launch in 2006 • See also RICE project for ground-based experiments and talk by Ad van den Berg (KVI). Conclusions and Outlook Cosmic rays are the pillars of astroparticle physics With LOFAR, LOPES the Netherlands have the chance to make a significant impact – there is a narrow window of opportunity Growing competition: Auger (Karlsruhe & Leeds – Alan Watson), Nancay radio experiment, HiRes?, various radio experiments for neutrinos Theory of Radio emission from air showers is now on solid physical ground: geosynchrotron is sufficient to explain basic results of historic data. LOPES starts to work: hardware, software, data reduction algorithms, integration with KASCADE (Grande). LOPES has found the first unambiguous CR event: highest time resolution ever (by a factor 10) and direct association with shower within 0.5° by digital beam forming (we can’t say what that means yet!). LOFAR can do lots of astroparticle physics! New method opens an entirely new parameter range. Interesting for Neutrino detection as well (needs more exploration). Joint operation with neutrino telescopes, gravity wave experiments?