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

•
Intro: Cosmic Rays
•
Radio Emission of CRs
–
Properties
–
Theory
•
LOFAR & LOPES
• Neutrinos …
•
Conclusions

• 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

3C273
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!

adopted from:
K. M annheim
(1998)
Multiplied by E 2.75
!

AGASA
HiRes I

• 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 10 20 eV one can do cosmic ray astronomy in the nearby universe.
1EeV = 10 18 eV
Cronin (2004)

• Up to 10 18 eV cosmic rays are predominantly Galactic.
•
At 10 18 eV we have

=10 9 for neutrons (m n
~1 GeV)
•
Neutron lifetime

=10 3 sec×10 9= 10 12 sec =10 4.5
yr
• This corresponds to a travel length of 10 kpc!
• Proton Larmor radius at 10 18 eV is
300 pc in Galactic B-field!
• Protons are isotropized – neutrons travel on straight lines.
• At 10 19 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 10 16 eV-- truly unimaginable for the time!
• 1960’s: Cosmic rays with energies of >10 19 eV detected - how are they made??
• Greisen, Zatsepin, Kuzmin (GZK): there should be a limit at ~5
X
10 19 eV

Longitudinal
- for different composition of primary -
Lateral
- for different secondary particles -

AUGER: 3000 km 2 ,1600 water tanks
& fluorescence

• 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

• 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 electronpositron pairs in the earth’s magnetic field
 highly beamed pulses of synchrotron radiation coherent emission at low frequencies
 emission on scales small compared to wavelength dominance of geomagnetic mechanism visible in past data
 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)

• 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

• The full LOFAR array will measure CRs from 2·10 14 eV to 10 20 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)

• 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”

•
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

• 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„
(10 15 -10 16 eV)

• 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”
(10 15 -10 16 eV)

KASCADE-Grande
The red dots show the location of new particle detectors: expansion of
KASCADE to KASCADE
Grande



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

Solar Burst
Integration: 1 ms
Frequency: 45-75 MHz
Bandwidth: 30 MHz
Antennas: 8
Resolution: ~3
°
Location: Karlsruhe
(research center)

dirty map cleaned map
simulated map
Solar Burst
Integration: 1 ms
Frequency: 45-75 MHz
Bandwidth: 30 MHz
Antennas: 8
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

Power after Beamforming







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
°.

• At 10 19 eV, horizontal neutrinos have 0.2% chance of producing a shower along a ~250 km track, 0.5% at 10 20 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
• R moon limb
~ 1740 km, so most detectable interactions are grazing rays, but detection not limited to just
• 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)

ANtarctic Impulsive Transient Antenna
Solar
Panels
ANITA
Gondola &
Payload
Antenna array
Cover (partially cut away)
600 km radius,
1.1 million km 2
• 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?