Experimental Estimation of Deviation Frequency within the Spectrum of Scintillations of the Carrier Phase of GNSS Signals

The term deviation frequency (fd) denotes the boundary between the variable part of the amplitude and phase scintillation spectrum and the part of uninformative noises. We suggested the concept of the “characteristic deviation frequency” during the observation period. The characteristic deviation frequency is defined as the most probable value of the deviation frequency under current local conditions. Our case study involved GPS, GLONASS, Galileo and SBAS data under quiet and weakly disturbed geomagnetic conditions (geomagnetic storm on 16 April 2021, Kpmax = 5, SYM-Hmin = −57 nT) at the mid-latitude GNSS station. Our results demonstrated that the deviation frequency for all signal components of GPS, GLONASS and Galileo varies within 15–22 Hz. The characteristic deviation frequency was 20 Hz for the mentioned GNSS signals. The SBAS differs from other systems: deviation frequency varies within 13–20 Hz. The characteristic deviation frequency is lower and equal to 18 Hz. We suggest the characteristic deviation frequency to determine the optimal sampling rate of the GNSS carrier phase data for the ionospheric studies. In turn, the deviation frequency can be considered as a promising index to estimate the boundary of non-variability of the ionosphere.

Measurement of the angular distribution of wavelength-shifted light emitted by TPB

We present measurements of the angular distribution of re-emitted light from tetraphenyl butadiene thin films when exposed to 128 nm light, which is the peak of the liquid Argon (LAr) scintillation spectrum, in vacuum. Films ranging from 250 nm to 5.5 μm in thickness are measured. All films were fabricated by evaporation deposition on ultraviolet transmitting (UVT) acrylic substrates. Preliminary comparisons of the angular distribution to that produced by a detailed Monte Carlo model are also presented. The current shortcomings of the model are discussed and future plans briefly outlined.

Experimental Estimation of Deviation Frequency Within the Spectrum of Scintillations of the Carrier Phase of GNSS Signals

The term deviation frequency denotes the boundary between the variable part of the amplitude and phase scintillation spectrum and the part of uninformative noises. We suggested the concept of the “characteristic deviation frequency” during the observation period which is defined as the most probable value of the deviation frequency under current local conditions. This work is a case study of the characteristic deviation frequency (fd) registered for GPS, GLONASS, Galileo and SBAS signals under quiet and weakly disturbed geomagnetic conditions in April 2021 at the mid-latitude GNSS station. Our results demonstrated that the fd value for all signal components of GPS, GLONASS and GALILEO signals varied within 15-22 Hz. The characteristic deviation frequency was 20 Hz for the mentioned GNSS signals. In difference, the deviation frequency was limited within 13-20 Hz for SBAS with the lower characteristic deviation frequency at 18 Hz. We assume that the concept of the characteristic deviation frequency can be used to determine the optimal sampling rate of the GNSS carrier phase data for the ionospheric studies. The characteristic deviation frequency can also characterize the state of the regular trans-ionospheric radio channel.

Morphology of solar system scale plasma lenses in the interstellar medium: a test from pulsar scintillation parabolic arcs

ABSTRACT Scintillation spectra of some pulsars have suggested the existence of ≲ AU scale density structures in the ionized interstellar medium, whose astrophysical correspondence is still a mystery. The detailed study of Brisken et al. suggested two possible morphologies for these structures: A parallel set of filaments or sheets (the ‘parallel stripes model’), or a filament broken up into denser knots (the ‘threaded beads model’). Here, we propose a straightforward test that can distinguish these two morphologies: Whether the apex of the main parabolic arc created by the scattered images deviates from the origin of the scintillation spectrum or not. In the ‘parallel stripes’ model, the scattered images move along the stripes as the relative position of the pulsar moves. As a result, the pulsar is always co-linear with the scattered images, and thus, the apex of the main parabolic arc stays at the origin of the scintillation spectrum. In the ‘threaded beads’ model, the scattered images remain at almost fixed positions relative to the density structures, and thus, the pulsar is not co-linear with the scattered images at most times, leading to an offset between the apex and the origin. Looking for this possible offset in a large sample of pulsar scintillation spectra, or monitoring the evolution of parabolic arcs will help pin down the morphology of these tiny density structures and constrain their astrophysical origin.

Resolution of the PSR 1919+21 Magnetosphere Emitting Region

Regular structure with 10 to 50kHz-scale was detected in the radio scintillation spectrum of PSR 1919+21. This regular structure may be a simple interferometric pattern formed by refractive multi-ray propagation between the pulsar and observer. It was found that the pulsar PSR 1919+21 radio emission scintillation spectrum phase changes significantly across the average profile. Within the refractive scattering scenario this phase-longitude dependence corresponds to a transversal shift of the magnetosphere emitting region of about 6 x 108 cm. The radio emission altitude is estimated to be near the light cylinder.