102 research outputs found
Modelling uncertainty of the radiation energy emitted by extensive air showers
Recently, the energy determination of extensive air showers using radio
emission has been shown to be both precise and accurate. In particular, radio
detection offers the opportunity for an independent measurement of the absolute
energy of cosmic rays, since the radiation energy (the energy radiated in the
form of radio signals) can be predicted using first-principle calculations
involving no free parameters, and the measurement of radio waves is not subject
to any significant absorption or scattering in the atmosphere. Here, we verify
the implementation of radiation-energy calculations from microscopic simulation
codes by comparing Monte Carlo simulations made with the two codes CoREAS and
ZHAireS. To isolate potential differences in the radio-emission calculation
from differences in the air-shower simulation, the simulations are performed
with equivalent settings, especially the same model for the hadronic
interactions and the description of the atmosphere. Comparing a large set of
simulations with different primary energies and shower directions we observe
differences amounting to a total of only 3.3 %. This corresponds to an
uncertainty of only 1.6 % in the determination of the absolute energy scale and
thus opens the potential of using the radiation energy as an accurate
calibration method for cosmic ray experiments.Comment: 8 pages, 2 figures, ICRC2017 contributio
Determination of the absolute energy scale of extensive air showers via radio emission: systematic uncertainty of underlying first-principle calculations
Recently, the energy determination of extensive air showers using radio
emission has been shown to be both precise and accurate. In particular, radio
detection offers the opportunity for an independent measurement of the absolute
energy scale of cosmic rays, since the radiation energy (the energy radiated in
the form of radio signals) can be predicted using first-principle calculations
involving no free parameters, and the measurement of radio waves is not subject
to any significant absorption or scattering in the atmosphere. To quantify the
uncertainty associated with such an approach, we collate the various
contributions to the uncertainty, and we verify the consistency of
radiation-energy calculations from microscopic simulation codes by comparing
Monte Carlo simulations made with the two codes CoREAS and ZHAireS. We compare
a large set of simulations with different primary energies and shower
directions and observe differences in the radiation energy prediction for the
30 - 80 MHz band of 5.2 %. This corresponds to an uncertainty of 2.6 % for the
determination of the absolute cosmic-ray energy scale. Our result has general
validity and can be built upon directly by experimental efforts for the
calibration of the cosmic-ray energy scale on the basis of radio emission
measurements.Comment: 22 pages, 3 figures, accepted for publication in Astroparticle
Physic
Refractive displacement of the radio-emission footprint of inclined air showers simulated with CoREAS
The footprint of radio emission from extensive air showers is known to exhibit asymmetries due to the superposition of geomagnetic and charge-excess radiation. For inclined air showers a geometric early-late effect disturbs the signal distribution further. Correcting CoREAS simulations for these asymmetries reveals an additional disturbance in the signal distribution of highly inclined showers in atmospheres with a realistic refractive index profile. This additional apparent asymmetry in fact arises from a systematic displacement of the radio-emission footprint with respect to the Monte-Carlo shower impact point on the ground. We find a displacement of ∼1500 m in the ground plane for showers with a zenith angle of 85°, illustrating that the effect is relevant in practical applications. A model describing this displacement by refraction in the atmosphere based on Snell’s law yields good agreement with our observations from CoREAS simulations. We thus conclude that the displacement is caused by refraction in the atmosphere
Systematic uncertainty of first-principle calculations of the radiation energy emitted by extensive air showers
The energy of extensive air showers can be determined from the energy radiated in the form of radio signals. The so-called radiation energy can be predicted with modern simulation codes using first-principle calculations without the need of free parameters. Here, we verify the consistency of radiation energy calculations by comparing a large set of Monte Carlo simulations made with the two codes CoREAS and ZHAireS. For the frequency band of 30 — 80 MHz, typically used by many current radio detectors, we observe a difference in the radiation energy prediction of 5.2%. This corresponds to a radio emission modelling uncertainty of 2.6% for thedetermination of the absolute cosmic-ray energy scale. Hence, radio detection offers the opportunity for a precise, accurate and independent measurement of the absolute energy of cosmic rays
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