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
Potential Sources
 Hillas plot: Gyro radius
has to fit source size!
 Galactic < 1017eV
Rgyr 
 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
ECR
eB
Radio Images of Cosmic Accelerators
Cygnus A
Cas A
NRAO/AUI
Fornax A
1.4 , 5, & 8.4 GHz
The Pierre Auger
Observatory
Auger: Clustering of
UHECRs
The beginning of “charged particle astronomy”!
AUGER Collaboration (2007), Science
9. Nov. (2007)
Ultra-high Energy Cosmic
Ray Spectrum
?
The Pierre Auger Collaboration, Physics Letters B (2010)
Depth of shower maximum
in atmosphere
Auger Composition Results
proton
prediction
Auger Data
prediction for
iron nuclei
Looks like
CR
primaries
become
more
heavy.
NB: HiRes
experiment
interprets
this
differently
(=> only
protons)
Cosmic Rays in the Radio
νMoon
S. Lafebre
Radio Astroparticle Physics:
 Cosmic Rays in atmosphere:
 Geosynchrotron emission
(10-100 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)
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
Coherent Geosynchrotron Radio
Pulses in Earth Atmosphere
Earth
B-Field  UHECRs produce particle
showers in atmosphere
~0.3 G
 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
coherent
E-Field
⇒ Etotal=Ne*Ee
⇒ Power ∝Ee2 ∝ Ne2
⇒ GJy flares on 20 ns scales
Falcke & Gorham (2003), Huege & Falcke (2004,2005)
Tim Huege, PhD Thesis 2005 (MPIfR+Univ Bonn
Cross Calibration of
LOPES10 and KASCADE
UHECR Particle Energy
B-field
Distance
Horneffer-Formula 2008
Energy and Composition
from MC Simulations
lateral radio profile  Xmax
radio flux  Ne
~5% showerLOPES
Data
to-shower
(Horneffer
et
fluctuations
al. 2007)
LOPES-KASCADE
Huege et al. 2008, (Astropart. Phys.) - REAS2 code
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
Nanosecond Radio Imaging
in 3D
 Off-line correlation of
radio waves captured
in buffer memory
 We can map out a 5D
image cube:
Actual 3D radio mapping of a CR burst
No simulation!
 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)
UHE Neutrino detection
needs large detector
volumes!
Auger: Aeff=3000 km2, Moon: Aeff=9×106 km2
Back to the moon …
Cosmic Ray
Westerbork
antennas
100 MHz Radio
Waves
Westerbork (WSRT)
Experiment
Westerbork Synthesis Radio Telescope
4 freq.
bands
4 freq.
bands
UHE Neutrino Limits from
WSRT νMoon Experiment
Anita ‘08
nMoon
Buitink et al. (2009), A&A - Scholten et al. (2009), Phys. Rev. Lett.
LOFAR Sensitivity to
Neutrinos
Singh et al. (2009)
LOFAR sensitivity to CRs
Singh et al. (2009)
Commissioning Results:
Triggering finally works
Horneffer/Corstanje/Falcke (Radboud)
Station Pulse Triggers in a
Day (Sky Distribution)
LOFAR low-band has all-sky
visibility!
A. Corstanje (Radboud)
5ms All-Sky Imaging with
LOFAR TBBs
Single LBA
station
S. Welles
L. Bähren
(Radboud)
5ms All-Sky Imaging with
LOFAR TBBs
Single LBA
station
S. Welles
L. Bähren
(Radboud)
Frequency 
Real-Time Detection and TBB
Dumping of Crab Giant pulse
Time 
Sander ter Veen
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
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 …
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.