A. W. Wernik

Behaviour of HILAT scintillation over spitsbergen

Results of the amplitude scintillation morphology of the HILAT satellite 137 MHz beacon transmission as measured at the Polish Polar Station at Hornsund, Spitsbergen (Δ = 73.4°) are presented. Seasonal, diurnal and latitudinal dependencies of scintillation intensity on magnetic activity were analyzed from over 2250 satellite passes recorded at solar minimum between April 1985 and March 1986. Regions with strong scintillation intensity appear to follow the auroral oval expansion and to move sunward with increasing level of magnetic activity. Maximum amplitude scintillation region coincides with the dayside cusp/cleft position during high magnetic activity. The dawn-dusk asymmetry in scintillation intensity is more distinct in winter than other months. The estimated summer/winter ratio of scintillation intensity is 1.4: 1. Numerical simulations compared with the observational results indicate that high latitude irregularities < 1 km are field-aligned and rod-like rather than sheet-like.

Variation of the ionospheric scintillation index with elevation angle of the transmitter

We have analyzed GPS data from 2007–2011 to determine the nature of variation of scintillation index with elevation of the direction of propagation at an observing point Warsaw, Poland, and Hornsund, Svalbard. To compare with the theory, the intensity scintillation index is simulated as a function of elevation angle, azimuth, magnetic field inclination, and shape of irregularities, using the phase screen model of scintillation as formulated by Rino (1979). Data analysis has been done for the seasonal as well as geomagnetic activity dependence of ionospheric scintillation. Scintillation index is a power-law function of the cosecant of the elevation angle. Results show that the power law strongly depends on the form of irregularities, being larger than in isotropic case for irregularities with dimension along the magnetic field direction smaller than those across the magnetic field. The present work also shows the need to use experimentally derived dependence on elevation.

Mid-latitude rocket measurements op plasma irregularities associated with topside density depletion

Abstract A plasma irregularities spectrum analyzer and a Langmuir probe experiment on a rocket experiment conducted at mid-latitudes during quiet night-time winter conditions revealed the existence of an isolated plasma density depletion between 700 and 1100 km. A substantial enhancement of intensity of the irregularities coinciding with the depletion was observed over a broad band of irregularity sizes ranging from tens of meters to several kilometers. The power spectral index was equal 0.84∓0.17 as compared to 1.71∓0.56 for the irregularities outside the plasma depletion.

Low latitude scintillations: A comparison of modeling and observations within the CIGALA project

Ionospheric scintillations can seriously jeopardize the reliability of the GNSS signals and consequently can cause significant error or outage on precise positioning applications. The threat is most acute at low latitudes where ionospheric irregularities are more likely to occur resulting in L-band signal scintillations. This paper describes the effort made to model the ionospheric scintillations over the Latin American region in the frame of the CIGALA project funded by the European GNSS Supervisory Authority within the 7th Framework Programme of the European Commission. Comparisons between the low-latitude model of scintillations and observations are here presented and discussed within the project perspectives.

B-Spline Model of Ionospheric Scintillation For – High Latitude Using In-situ Satellite Data

Ionospheric scintillation is a popular phenomenon among space scientists and GNSS users. It has been widely discussed and studied in past but still difficult to model and predict on large scales. Ionospheric scintillations are caused by rapid random variations of the phase and amplitude of the radio waves passing through the ionosphere. As the signal propagation continues after passing through the region of irregularities in the ionosphere, phase and amplitude scintillation develops through interference of multiple scattered waves. After propagation to a receiver, the irregular phase may combine either constructively or destruc‐ tively to increase or decrease the wave amplitude. Another possibility is that the cause of either increased or decreased phase velocity may be refractive when an electromagnetic wave enters a medium [8].

Detecting travelling ionospheric disturbances in incoherent scatter data using the Maximum Entropy Method

Abstract Two different methods of determining autoregressive coefficients in Maximum Entropy Method (MEM) were compared, investigating power spectra of synthetic signals consisting of three sinusoids and white noise of relatively high level. Spectral line shifts due to the initial phases changes were evaluated. Burgs method was chosen for determining power spectra of experimental signals. Simulating the incoherent scatter data obtained with EISCAT, it was shown that the increasing noise and wave attenuation effects are difficult to separate. Integrating the ME spectral density it was found that, in many cases, it is impossible to reproduce the true power of each harmonic of the signal.