Perturbations of GPS signals by the ionospheric irregularities generated due to HF‐heating at triple of electron gyrofrequency

Abstract

The objective of this letter is to present the first experimental evidence of perturbations of GPS signals by the electron density irregularities caused by the HF‐heating of the F2 region of the ionosphere. The experiments were conducted using the HAARP heater having the radiating frequency f which matches 3 fB, i.e., triple the local electron gyro frequency. Such frequency is expected to generate super small irregularities of the electron density which can scatter GPS signals. It was found that the differential phase of the probe GPS signals changed abruptly in about 10 s after the start of the HF‐heating, and then oscillated with the heating period 20 s. The oscillations lasted for 4–5 minutes and then disappeared, presumably when the resonance condition f = 3 fB was not satisfied, although the HF‐heating continued. The phase oscillations indicate the presence of small scale irregularities of the electron density caused by the HF‐heating at the frequency matching 3 fB.

Sounding of the ionosphere disturbed by the “Sura” heating facility radiation using signals of the GPS satellites

“…Thus, the space between the magnetic zenith for the pump wave and the magnetic zenith proper turns out to be peculiar from the viewpoint of the most effective interaction of the high-power radio wave with ionospheric plasma and the generation of artificial ionospheric turbulence in it. Note that the enhancement of TEC variations with the approach of the satellite beam to the magnetic-zenith region was also observed in [17][18][19].…”

“…However, if we assume that the obtained value of the TEC decrease down to 0.1 TECU is only determined by the plasma-density variation in the pump-wave reflection region, then the estimate could be ΔN/N ≈ −20%, which should certainly be regarded as exaggerated by an order of magnitude or more. It should be mentioned that the authors of [18,19] also admitted that the plasma-density variations due to the ionosphere heating by high-power HF radio emission, which were obtained from the TEC measurements, are inexplicably large. For the admissible values of ΔN/N ≈ −1%, the longitudinal (along the satellite beam) sizes of the region with decreased plasma density for measured values of the TEC decrease should have been about 300 km, i.e., such a region should, of course, comprise the altitudes of the outer ionosphere, as well.…”

“…Under the midlatitude conditions, the characteristics of these inhomogeneities were studied by the method of aspect scattering of HF and UHF radio waves [1,9,15], raying of the disturbed region by signals of low-orbit satellites [1,9], using satellite radio tomography [13,16], etc. Recently, the methods of sounding of the disturbed region by radio signals of the GPS/GLONASS satellies at frequencies 1.2-1.6 GHz [17][18][19] and direct measurements of the properties of the plasma turbulence by onboard equipment of the satellites flying through the disturbed magnetic flux tube resting on the generation region of intense artificial ionospheric turbulence near the level of reflection of the high-power radio wave [20,21] have evolved. These measurements gave new important information on the plasma disturbances induced by the high-power radio wave and highlighted a number of topical problems, among which the question concerning the structure of the disturbed ionosphere region is one of the most important.…”

Study of GNSS-measured ionospheric total electron content variations generated by powerful HF-heating

“…The parameters of these irregularities were studied by the methods of field-aligned scattering of VHF/UHF radio waves (Frolov et al, 1997); radio probing of the heated region by radio transmissions from low-orbiting satellites (Erukhimov et al, 1987;Leyser, 2001); ionospheric radio tomography (Tereshchenko et al, 2004;Frolov et al, 2007) and other. Recently, methods for sounding of the heated ionosphere by radio signals from high-orbiting navigational GNSS satellites at frequencies 1.2-1.5 GHz started to develop (Tereshchenko et al, 2008;Milikh et al, 2008). These methods are widely used and provide interesting data in ionospheric research (Bust and Mitchell, 2008), particularly in studies of ionospheric effects of extreme heliogeophysical events, such as magnetic storms (Kunitsyn et al, 2004;Jin et al, 2008), solar flares (Tsurutani et al, 2005;Kunitsyn and Padokhin, 2007) and eclipses (Afraimovich et al, 1998), etc. In this article, we present the experimental results of the influence of electron density perturbations produced by the high-frequency heating of the F2 layer of the dayside midlatitude ionosphere on the GNSS signals.…”

“…These methods are widely used and provide interesting data in ionospheric research (Bust and Mitchell, 2008), particularly in studies of ionospheric effects of extreme heliogeophysical events, such as magnetic storms (Kunitsyn et al, 2004;Jin et al, 2008), solar flares (Tsurutani et al, 2005;Kunitsyn and Padokhin, 2007) and eclipses (Afraimovich et al, 1998), etc. In this article, we present the experimental results of the influence of electron density perturbations produced by the high-frequency heating of the F2 layer of the dayside midlatitude ionosphere on the GNSS signals. Though the similar studies were carried out before (Tereshchenko et al, 2008;Milikh et al, 2008), our work presents the first attempt to investigate spectral characteristics of observed TEC variations for a number of heating modes with different time-modulations of effective radiated power. The paper is organized as follows.…”