1. Heino Falcke Radboud University, Nijmegen ASTRON, Dwingeloo
LOFAR Cosmic Ray KSP
Heino Falcke Radboud University, Nijmegen ASTRON, Dwingeloo

2. What we (don’t) know about UHECRs
We know:
their energies (up to 1020 eV).
their overall energy spectrum
We don’t know:
where they are produced
how they are produced
what they are made off
exact shape of the energy spectrum

3. Potential Sources Hillas plot: Gyro radius has to fit source size!
Galactic < 1017eV
Supernovae
neutron stars & stellar black holes
Extragalactic >1018 eV
Supermassive black holes
Gamma-Ray bursts
Intergalactic shocks
Top-down: decay of primordial superheavy particles (?)
1 EeV = 1018 eV

4. Radio Images of Cosmic Accelerators
Cygnus A
Cas A
NRAO/AUI
Fornax A
1.4 , 5, & 8.4 GHz

5. The Pierre Auger Observatory

6. Auger: Clustering of UHECRs
The beginning of “charged particle astronomy”!
1set until May 24: 12/15 correlate
2ns set until May 24- August: 8/12 correlate (2.7 expected)
For combined set: 20 out of 27 cosmic rays events
236 correlate with at least one of the 442 selected AGN (292 in the eld of view
237 of the Observatory), while only 5.6 are expected on average to do so if the
238 ux were isotropic (p = 0:21)
µG B-fields and kpc scales needed
AUGER Collaboration (2007), Science
9. Nov. (2007)

7. Ultra-high Energy Cosmic Ray Spectrum?
The Pierre Auger Collaboration, Physics Letters B  (2010) 

8. Auger Composition Results
Looks like CR primaries become more heavy.
NB: HiRes experiment interprets this differently (=> only protons)
proton prediction
Depth of shower maximum in atmosphere
Auger Data
prediction for iron nuclei

9. Cosmic Rays in the Radio
Countrate at
10^17eV: 10^5 events
10^18 eV: ~ (lower and upper curve)
10^19 eV: 4
cnv[3 10^15 /(Meter^2 Second sr eV^-1.5)/(10^18 eV)^2.5 Pi sr (Pi km^2)* Year 10^18 eV]
νMoon
S. Lafebre

10. Radio Astroparticle Physics:
Cosmic Rays in atmosphere:
Geosynchrotron emission ( MHz)
Radio fluorescence and Bremsstrahlung (~GHz)
Radar reflection signals (any?)
VLF emission, process unclear (<1 MHz)
Neutrinos and cosmic rays in solids: “Cherenkov emission” (100 MHz - 2 GHz)
polar ice cap (balloon or satellite)
inclined neutrinos through earth crust (radio array)
CRs and Neutrinos hitting the moon (telescope)

11. LOFAR Cosmic Ray KSP: Main Goals
Understand High-Cosmic Rays
Measure and fully characterize radio signals of extensive air showers (e.g., reference calibration for LOFAR and AUGER).
Understand effects of and on lightning
Use radio technique in transition region from Galactic to extragalactic CRs to clarify their nature (i.e., composition)
Search for radio flashes from the moon to characterize UHECR spectrum at highest energies (NuMoon)
Develop the techniques to work on raw time series data on dipole-level (transient buffer board & tied-array beam) in near field and far-field.
Science Synergy with other KSP
Transients: Identify and understand other sporadic signals (“RFI”, lightning, SETI, astrophysical sub-ms pulses, e.g. giant pulses)
Survey: Identify sources of UHECRs

12. Coherent Geosynchrotron Radio Pulses in Earth Atmosphere
Earth B-Field ~0.3 G
UHECRs produce particle showers in atmosphere
Shower front is ~2-3 m thick ~ wavelength at 100 MHz
e± emit synchrotron in geomagnetic field
Emission from all e± (Ne) add up coherently
Radio power grows quadratically with Ne
Etotal=Ne*Ee
Power ∝Ee2 ∝ Ne2
GJy flares on 20 ns scales
shower front e± ~50 MeV
Geo- synchrotron
coherent E-Field
Falcke & Gorham (2003), Huege & Falcke (2004,2005) Tim Huege, PhD Thesis 2005 (MPIfR+Univ Bonn

13. Cross Calibration of LOPES10 and KASCADE
UHECR Particle Energy
B-field
Distance
Horneffer-Formula 2008

14. Energy and Composition from MC Simulations
lateral radio profile  Xmax
radio flux  Ne
LOPES Data
(Horneffer et al. 2007)
~5% shower-to-shower fluctuations
LOPES-KASCADE
Huege et al. 2008, (Astropart. Phys.) - REAS2 code

15. Imaging of CR radio pulses with LOPES
A. Nigl 2007, PhD
Horneffer, LOPES30 event
See also Falcke et al. (LOPES collaboration) 2005, Nature, 435, 313

16. Nanosecond Radio Imaging in 3D
Actual 3D radio mapping of a CR burst No simulation!
Off-line correlation of radio waves captured in buffer memory
We can map out a 5D image cube:
3D: space
2D: frequency & time
Image shows brightest part of a radio airshower in a 3D volume at t=tmax and all freq.
Bähren, Horneffer, Falcke et al. (RU Nijmegen)

17. UHE Neutrino detection needs large detector volumes!
Auger: Aeff=3000 km2, Moon: Aeff=9×106 km2
Back to the moon …

18. Cosmic Ray
Westerbork antennas
100 MHz Radio Waves

19. Westerbork (WSRT) Experiment
4 freq. bands
4 freq. bands
Westerbork Synthesis Radio Telescope

20. UHE Neutrino Limits from WSRT νMoon Experiment
Anita ‘08
nMoon
Buitink et al. (2009), A&A - Scholten et al. (2009), Phys. Rev. Lett.

21. LOFAR Sensitivity to Neutrinos
Singh et al. (2009)

22. LOFAR sensitivity to CRs
Singh et al. (2009)

23. Commissioning Results: Triggering finally works
Horneffer/Corstanje/Falcke (Radboud)

24. Station Pulse Triggers in a Day (Sky Distribution)
LOFAR low-band has all-sky visibility!
A. Corstanje (Radboud)

25. 5ms All-Sky Imaging with LOFAR TBBs
Single LBA station
S. Welles
L. Bähren (Radboud)

26. 5ms All-Sky Imaging with LOFAR TBBs
Single LBA station
S. Welles
L. Bähren (Radboud)

27. Real-Time Detection and TBB Dumping of Crab Giant pulse
Frequency 
Dispersed Pulse
Time 
Sander ter Veen

28. LOFAR Air Shower Array Layout:
5 clusters of 4 particle detectors in LOFAR core
RFI measurements in ASTRON’s antenna chamber
Hardware & DAQ software is ready, testing under way, installation is next
Will provide CR triggers to core stations

29. Synergies with other KSPs
Technical:
Identification of steady nearby and transient RFI sources
Dipole-based antenna calibration and monitoring (gain, polarization)
TBB software (mainly with TKP)
Scientific;
TKP: FRATs – triggering and identification of Fast Radio Transients
Surveys: Make survey products accessible to CR community
Catalog of radio sources with estimates of sizes, magnetic fields, jet powers …

30. Summary & Conclusions
We want to explore the fastest time scales in LOFAR (down to 5ns) and develop novel techniques in radio astronomy
Real-time triggering
Transient Buffer-Board (TBB) utilization
3D all-sky imaging on buffered data (1sec observation needs 1TB of data to be processed…)
Transient signal extraction
detect airshowers from UHECRs between 1017 and 1019 eV
determine radio properties with unprecedented quality (e.g., input for AUGER)
determine precisely energy and composition in the suspected transition region form Galactic to Extragalactic CRs
search for UHECRs and Neutrinos >1021 eV hitting the moon
Verify GZK-cutoff
at the very least place the best limits on super-GZK CRs and neutrinos (which SKA will surely detect)
investigate and search for other sub-second signals in buffered data and collaborate with Transient KSP
Giant pulses of pulsars
coherent burst from exploding neutron stars, etc.
Lightning
SETI (One Second All-Sky Survey)
provide a catalog of northern UHECR source candidates with Survey KSP.