Impact of biaxial birefringence in polar ice at radio frequencies on signal polarizations in ultra-high energy neutrino detection. (arXiv:2110.09015v2 [astro-ph.IM] UPDATED)

Impact of biaxial birefringence in polar ice at radio frequencies on signal polarizations in ultra-high energy neutrino detection. (arXiv:2110.09015v2 [astro-ph.IM] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Connolly_A/0/1/0/all/0/1">Amy Connolly</a>

It is known that the Antarctic ice sheet is birefringent and that this can
have implications for in-ice radio detection of ultra-high energy neutrinos.
Previous investigations of the effects of birefringence on the propagation of
radio-frequency signals in ice have found that it can cause time delays between
pulses in different polarizations in in-ice neutrino experiments, and can have
polarization-dependent effects on power in radar echoes at oblique angles in
polar ice. I report, for the first time, on implications for the received power
in different polarizations in high energy neutrino experiments, where the
source of the emitted signal is in the ice, a biaxial treatment at radio
wavelengths is used, and the signals propagate at oblique angles. I describe a
model for this and validate it against published results from the SPICE in-ice
calibration pulser system at South Pole, where unexpectedly high
cross-polarization power has been reported for some geometries. The data shows
behaviors consistent with a biaxial treatment of birefringence inducing
non-trivial rotations of the signal polarization. These behaviors include, but
are not limited to, an interference effect that would leave an imprint in the
power spectrum. This would serve as both an in-ice neutrino signature and a
measurement of the distance to the interaction. While further work is needed, I
expect that proper handling of the effects presented here will increase the
science potential of ultra-high energy neutrino experiments, and may impact the
optimal designs of next-generation detectors.

It is known that the Antarctic ice sheet is birefringent and that this can
have implications for in-ice radio detection of ultra-high energy neutrinos.
Previous investigations of the effects of birefringence on the propagation of
radio-frequency signals in ice have found that it can cause time delays between
pulses in different polarizations in in-ice neutrino experiments, and can have
polarization-dependent effects on power in radar echoes at oblique angles in
polar ice. I report, for the first time, on implications for the received power
in different polarizations in high energy neutrino experiments, where the
source of the emitted signal is in the ice, a biaxial treatment at radio
wavelengths is used, and the signals propagate at oblique angles. I describe a
model for this and validate it against published results from the SPICE in-ice
calibration pulser system at South Pole, where unexpectedly high
cross-polarization power has been reported for some geometries. The data shows
behaviors consistent with a biaxial treatment of birefringence inducing
non-trivial rotations of the signal polarization. These behaviors include, but
are not limited to, an interference effect that would leave an imprint in the
power spectrum. This would serve as both an in-ice neutrino signature and a
measurement of the distance to the interaction. While further work is needed, I
expect that proper handling of the effects presented here will increase the
science potential of ultra-high energy neutrino experiments, and may impact the
optimal designs of next-generation detectors.

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