LOFAR CKP: Main Motivation

Exploring the sub-second transient radio sky:Extensive Air showers as guaranteed signalRadio flashes from the moon (UHECR and

other?)Identify and understand other sporadic signals

(“RFI”, lightning, SETI, astrophysical sub-ms pulses with TKP)

Develop the techniques to work on raw time series data (transient buffer board & tied-array beam) in near field and far-field.

Astroparticle Physics:Radio Detection of Particles

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)

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 producedwhat they are made offexact shape of the

energy spectrum

Auger: UHECR Spectrum

Reliable energy spectrum up to >1020 eV from surface detectors (SD)

Evidence for a suppresion above 1019.6 eV

Interaction of UHECRs with cosmic microwave background (“GZK cut-off”)?

UHECRs are extragalactic

Auger 2007, ICRCdivided by E-3

30 expected for E-2.6, 2 seen

Auger: Clustering of UHECRs

New data confirms correlation with AGN clustering. Chance probability: 2× 10-3

The beginning of “charged particle astronomy”!

AUGER Collaboration (2007), Science 9. Nov. (2007)

Ultra-High Energy (Super-GZK) Neutrino Detections

Ultra-high energy particle showers hitting the moon produce radio Cherenkov emission (Zas, Gorham, …).

This provides the largest and cleanest particle detector available for direct detections at the very highest energies.

In the forward direction (Cherenkov cone) the maximum of the emission is in the GHz range.

Current Experiments: ANITA GLUE FORTE RICE

from Gorham et al. (2000)from Gorham et al. (2000)

radio from neutrinos hitting the moon

LOFAR Moon experiment

Detectability of super-GZK cosmic rays and neutrinos hitting the moon

What are UHECRs made of? Current Methods:

Fluorescence+ Sees entire shower

evolution+ Oversees large volume- Only works during clear,

moonless nights (10% duty cycle)

- Light absorption by aerosols

Cherenkov particle detectors+ Works 100% of time+ Well studied- Only sees particles

reaching ground- Local detection only

Longitudinal Shower Profile

Depth

in

Atm

osp

here

Particle Number

Coherent Geosynchrotron Radio Pulses in Earth Atmosphere

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 Ne

2

GJy flares on 20 ns scales

coherentE-Field

show

er front

e± ~

50 M

eV

Geo-synchrotron

Falcke & Gorham (2003), Huege & Falcke (2004,2005) Tim Huege, PhD Thesis 2005 (MPIfR+Univ Bonn

EarthB-Field~0.3 G

Radio CR Simulation Results:Extraction of Energy & Nmax

Hu

eg

e e

t al. (in

pre

para

tion

)Shower-to-Shower fluctuation is only 5%!

Radio Pulse Shape: Imprint of Shower Evolution

Tim

Hu

eg

e e

t al. (2

00

7)

|E|

(µV

/m)

t (ns)

Extraction of Composition and Xmax from Curvature

Lafebre et al. (2008), PhD

Huege et al. (2008)

CRs with LOFAR (100xLOPES):

LOFAR:

~900 dipoles will see one shower2

x 2

km

2 c

ore

are

a

Antenna fields

Every dipole has a 1s “Transient Buffer” storing the full electro-magnetic wave information (all-sky, all-frequency)!

Experimental Realization: Transient Buffer Board

© ASTRON

Transient Buffering

COMPENSATECABLE LENGTHDIFFERENCES

DETECT

TRANSIENTS

FREEZE ONTRIGGER

(from RCU)antenna

dataSEPARATESUBBANDS

select

Detection control

(to CEP)Transient

buffer data

Store/Read-outcontrol

Subbanddata

Receiver banddata

Local Control Unit

Trigger

External triggerG. trigger

Beam Forming

Antenna-Beam

Station-Beam (T

ied)

Arr

ay-B

eam

Inco

he

rent

Stat

ion

-Bea

m

Phased Array Beam Steering

LOFAR low-band element receives radiation from all directions.

Phased Arrays have a virtual steerable “focal surface” which can be adapted “at will”.

Buffering raw-data in each antenna allows offline beam steering.

Normal far-field imaging is just inclining a plane.

Phased Array Beam Steering

Curving the virtual “focal surface”

allows near-field imaging.

Offline processing allows one to

scan an entire volume at all

frequencies and time ranges.

Search for fast and unpredictable

bursts.

Distinguish cosmic from terrestrial

effects.

Imaging of CR radio pulses with LOPES

See also Falcke et al. (LOPES collaboration) 2005, Nature, 435, 313

Horneffer, LOPES30 event

A. Nigl 2007, PhD

Nanosecond Radio Imaging in 3D

Off-line correlation of radio waves captured in buffer memory

We can map out a 5D image cube:3D: space2D: 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)

Actual 3D radio mapping of a CR burst No simulation!

Observing Time

UHEP/Moon: Initially 1 month of accumulated observing time under good ionospheric

conditions sensitivity that is orders of magnitude better than the sensitivity of existing

experiments Extend to three months to reach UHECR-extrapolation and show GZK cut-off

VHECR mode A: About 1 month of accumulated observing time 1000 good events.

VHECR mode B: Continuous observations, and at least 1/3 of the time with the low-band

antennas. HECR:

based on availability of resources TS-mode: triggered by dynamic spectrum – indicating unusual radio

conditions (e.g. lightning) One-Second All Sky Survey (OSASS) – Take several full-buffer dumps and

image entire sky (Flux calibration and transient search) Map tied array data (Calibration for Moon and transient search)

Cosmic Rays in the Radio

νMoon

S. Lafebre

Summary

Technical goal of CKP: Tempo-spatial properties of sub-second radio flares

UHECRs:Understand the radio emission properties of extensive

airshowers in great detail Precise composition analysis of CRs (“What are they?”) Precise localization of UHECRs (“Where do they come from”?) Closely interact with AUGER observatory (Radio@Auger, MAXIMA).

Improve limits on super-GZK CRs to meaningful values.Explore other methods (passive radar, isotropic emission?)

Be open for other and new fast radio phenomena:Lightning investigation (with KNMI – Dutch Meteorological Inst.)Lunar radio flares from meteorite impactsSearch for astrophysical sub-second radio bursts:

One-Second All-Sky Survey (OSASS)Transient SETI (here rely on open-source/open-data model)

Conclusions

Challenges for UHECRs in the future: getting better composition and energy analysis (to reduce uncertainty in

GZK cut-off determination estimate) Get even better directional information to improve clustering analysis &

identify sources Get to the super-GZK particles Become bigger, better, cheaper, & smarter

Radio emission of UHECR should give: excellent energy resolution (5%?) precise 3D localization and imaging (~0.1°) Composition from shower front and pulse shape high duty cycle

With Auger “charged particle astronomy” has begun: GZK cutoff, AGN correlation, …

With Radio high-precision particle astronomy will begin But this requires still a significant experimental effort ...