Dave Z. Besson, KU, Lawrence, KS

N.B. The Radio Waves being detected are secondary, producedby collisions of cosmic rayswith matter. -i.e., NOT a radio dish detecting direct radiowaves from astronomical sources

Radiowave detection of UltraHighEnergy Particles(esp. cosmic rays [protons, and other things that fall from the sky

Taglines

1) We are entering the era of 'multi-messenger' astronomyComprehensive picture of astronomical sources by combining multiple EM wavelengths + particles, viz. Neutrinos and protons2) In addition to direct detection of radio sources in the sky, RF detection also includes radio emissions from both neutrino- and charged-CR-induced `showers' (=`indirect' probe)

Plans are underway to outfit proposed Auger North experiment with radio detectors for charged-CR measurements

NSF/DOE support for $150M experiment uncertainNSF project to develop Askaryan Radio Array at the South Pole

($4.3M) for neutrino detection + charged-CR capabilities

Radiowave CRdetection papersas f(ICRC year)(Badran/Weekes)

Some History

Pierre Auger (1899-1993) realizes that cosmic rays are `extensive'

`hits' distributed over large area are coincident in time

-Cloud chambers @3500 m & sea level-Coincidences @ 1 microsecond

conclusion: E>1015 eV (1 PeV)

1961: First attempts to directly “confront” CR's

Lee et al., Four, Fant., Vol. 1, p. 1 (1961)

Radio Detection of cosmic rays, 2009

Two techniques:

● 1) Measurement of geosynchrotron RF emissions as extensive air showers develop

● Detection of primary charged CR's; E>1 PeV● Antennas in-air viewing shower core at, e.g., 600

g/cm2 depth in atmosphere● 2) Measurement of coherent RF radiation from

EM&hadronic showers in dense media ● Detection of neutrinos and/or charged CR's producing

showers that penetrate into the medium itself● In both cases, the physical scale of the charge separation 

sets the scale of the sensitive RF detector● Geosynchrotron: Tens of meters=>~50 MHz● Showers: 10 cm Moliere Radius=>100­1000 MHz

Coherent Geosynchrotron Radio Pulses in Earth Atmosphere

UHECRs produce particle showers in atmosphereShower front is ~2-3 m thick ~ wavelength at 100 MHze± emit synchrotron in geomagnetic fieldEmission from all e± (Ne) add up coherentlyRadio power grows quadratically with Ne

Etotal=Ne*Ee

Power ~Ee2 ~ Ne

2

GJy flares on 20 ns scalescoherentE-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 Emission from Air Showers: A Very Brief History

Initial motivation through prediction of Cherenkov-like radio emission process (Askaryan 1962).Radio pulse discovery at Jodrell Bank at 44 MHz (Jelley et al. 1965). Various experiments around the world but problems with data acquisition (oscilloscopes!) and interference.Death and resurrection of radio detection:ICRC 1975, Watson radio obituary: ‘… it is clear that experimental work on radio signals has been terminated elsewhere'.ICRC 1977, Harold: 'The logical decision is to abandon radio emission as a tool in air shower investigations…”ICRC 2007, plenary lecture on “Radio Detection of UHECRs” and many other contributions~2001 Peter Biermann points out potential relevance for LOFAR radio telescope

Jelley et al. (1965)Jelley et al. (1965)

Oscilloscope traces of CR radio pulses

Frequency spectrum as f(impact parameter relative to shower core)

|E|

(µV

/m/M

Hz )

v (MHz)

Hu

eg

e e

t al . (2

00

5)

20 m140 m

260 m380 m500 m

Coherence|Incoherence

Low Frequency Radio Array in Europe (~1/4 completed)provides radiowave detection of air showers, as well.

Claim: 100 PeV shower seen by 900 dipoles with ~ns timing!

AUGER NORTH, eastern Colorado (2010-)will also include radio component

Calibrating radiowave air shower detection in Russia

*Test technique at Tunka Valley, Siberia (July, 2008)

2) RF neutrino detection in-media Flux standard=`GZK' (charged CR photoproduction on CMB produces pions...)

What detection volume is needed?Flux of GZK neutrinos < 1 neutrino / km2 / year / steradian

Neutrino interaction length is ~500 km in water (Eν ≈ 1019 eV), so an incident neutrino at Eν ≈ 1019 eV has ~0.002 chance of interacting in 1 km of water.

- Detector can see at most half the sky – Earth blocks upcoming neutrino. Therefore, rates in detector are ~0.02 neutrinos / km3 / year

Need to thoroughly monitor at least 50 km3 to see only 1 event in a year!

A detector > 1000 km3-sr is required

To obtain a detection volume this large, one must use:emission with large S/N

natural materials in situ with long attenuation length, uniform, and

A LOT OF IT-moon rock, salt domes(?), Antarctic ice...

How MIGHT we detect cosmic ray neutrinos in Antarctica?

“ACME trap”(denise braun, 12/03)

Beyond 10 km3?Two Good Ideas by Askaryan

#1. UHE event will induce an e/γ shower:

In electron-gamma shower in matter (ice, e.g.), there will be 20% more electrons than positrons.

Compton scattering: γ + e-(at rest) → γ + e-

Positron annihilation: e+ + e-(at rest) → γ + γ

Two Good Ideas by Askaryan

#2. Excess charge moving faster than c/n in matter emit Cherenkov Radiation

Each charge emits field |E| ∝ eik•r

and Power ∝ |Etot|2

Width of cone~FT(lateral shower size)In dense material RMoliere~ 10cm

λ<<RMoliere (optical case), random phases⇒ P∝N λ>>RMoliere (microwaves), coherent ⇒ P∝ N2

ννν dddPCR ∝

Modern simulations (Razzaque et al.)

cherenkov

Cherenkov Radiation is 100% Polarized

USE

Reconstructed signal is a brief, unresolved, bipolar pulse of radiation

Details of analysis in PRD 74, 043002 (2006)

Experimental Realizations of in-ice RF neutrino detection

RICE: 1996-present-16 in-ice antennas at South Pole, co-deployed in IceCube holes to depths of 100-300 m. + above-surface RxCoaxial cable signal transmission to surface digitization

ANITA: 2001-present--32 dual-polarization horns mounted on balloon, synoptic viewing of Antarctica during ~30-day circumpolar flight. 2nd flight completed Jan 2009.

--ARA: Askaryan Radio Array: planned 80 km2 areal coverage, in review @NSF now!

Must understand RF properties of the target? I.e., is ice 'simple' (`vanilla'?)

Taylor Dome Basecamp –in situ measurements of RF properties(Astropart.Phys.29:130-157,2008)

Know your medium! Have done radio transmission studies at Taylor Dome & SP

BottomReflectionStudies.

Horn antennas send waves polarized along two perpendicular axes

Tagline: “Attenuation Length”~1 km (~50x higher than for visible light).

Note time delay between HH-polarization and VV-polarizationbirefringence!

DATA: Received echo for two polarizations

Antarctic Impulsive Transient Antenna (ANITA): 'synoptic' strategy

ANITA Goal: Pathfinding mission for GZK neutrinos - 1st launch Dec. 15, 2006 – Jan. 20, 20072nd flight: December 20, 2008 – Jan. 24, 2009 (3rd orbit)

M. R

osen, Univ. of

Haw

aii

ANITAGondola &

Payload

Antenna arrayCover (partially cut

away)

Solar Panel

s

ANITA concept: View the Antarctic continent from above!

пуск

После выпуска

ANITA­1: No Vpol neutrino candidates (PRL 103, 051103, 2009), but some Hpol candidates survive. Reflected geosynchrotron? (prelim!)

Also, sensitive to particles with long ionization trail (monopoles, e.g.)

Preliminary Result

• This preliminary limit exceeds any experimental limit to date.

6 7 8 9 10 11 12 13

1,00E-024

1,00E-023

1,00E-022

1,00E-021

1,00E-020

1,00E-019

1,00E-018

1,00E-017

1,00E-016

1,00E-015

1,00E-014

Relativistic Monopole Flux Limit

ANITA 2Freese (Theory)RICE (Daniel)MACROAMANDADimopolous (Theory)

Log Gamma

Flu

x L

imit

(cm

^ 2*s

*sr)

-̂1

ANITA drawbacks: 1) inability to see into ice,2) R

0~100 km=>HIGH threshold

Peak of GZK neutrino spectrum~100 PeVcanonical: S:N=1:1 for 1 PeV for 1 PeV nu at R=km

Basic idea: 'close' stations;each station performs

reconstruction!

Calibration/testing at UW

Calibration and environmental testing in Lawrence,

the Checkers supermarket vegetable freezer

•Radiowaves offer a technique for EHE neutrino detection, BUT need a big, dense target, and neutrino “crashes” are rare. Radio also can be used to detect other CR particles hitting Earth•RICE data-taking continues, with added radiowave air shower detection added.

•ARA testbed•ANITA second flight completed; third planned

•For the possible grad students out there, if you’ve ever wanted to experience: * <8 hr/day Facebook access (but getting better!!!) * long, lonely days/nights cut off from civilization * a barren, desolate and foreboding landscape This could be your opportunity!

*(not really)