Modulation of radio frequency signals by ULF waves

Waters, C. L.; Yeoman, T. K.; Sciffer, M. D.; Ponomarenko, P. V.; Wright, D. M.

doi:10.5194/angeo-25-1113-2007

Cited by 13 publications

(15 citation statements)

References 46 publications

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“…Signatures of ULF waves have been seen in both the ionosphere and ground scatter returns (Walker et al, 1979;Fenrich et al, 1995;Yeoman et al, 2000;Ponomarenko et al, 2001;Baddeley et al, 2002;Ponomarenko et al, 2005;Fenrich et al, 2006;Waters et al, 2007). The radars can detect ULF signatures when the spatial scale prevents the signal appearing at the ground (Yeoman et al, 2000;Yeoman and Wright, 2001;Baddeley et al, 2002).…”

Section: Discussionmentioning

confidence: 99%

“…However, to obtain more complete information, ULF data are required over a spatial region in the ionosphere. A few spatial measurements of ULF waves in the ionosphere have been obtained using Dopppler sounding techniques (Yeoman et al, 2000;Baddeley et al, 2005;Waters et al, 2007). ULF scale sizes down to 50 km have been observed for latitudes near L=6 (Baddeley et al, 2005).…”

Section: Discussionmentioning

confidence: 99%

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ULF wave effects on high frequency signal propagation through the ionosphere

Waters

Cox

2009

Ann. Geophys.

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Abstract.Variations in the total electron content (TEC) of the ionosphere alter the propagation characteristics of EM radiation for frequencies above a few megahertz (MHz). Spatial and temporal variations of the ionosphere TEC influence highly sensitive, ground based spatial measurements such as those used in radio astronomy and Global Positioning System (GPS) applications. In this paper we estimate the magnitudes of the changes in TEC and the time delays of high frequency signals introduced by variations in the ionosphere electron density caused by the natural spectrum of ultra-low frequency (ULF) wave activity that originates in near-Earth space. The time delays and associated phase shifts depend on the frequency, spatial structure and amplitude of the ULF waves.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

ULF wave effects on high frequency signal propagation through the ionosphere

Waters

Cox

2009

Ann. Geophys.

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“…The coupled MHD equations describing these modes in an anisotropic collisional plasma can be found in Waters et al (2007) and Fedorov et al (2016). The vertical profile of local of the ionospheric parameters (conductivity tensor, Alfven velocity, electron mobility tensor, etc.)…”

Section: Possible Mechanisms Of Tec Modulation By Mhd Wavesmentioning

confidence: 99%

“…Low-Earth orbit satellites can detect a high-frequency part only of ULF spectrum (Pc1-3 waves). Ionospheric signatures of long-period ULF waves (Pc4-5, Pi2-3) can be detected by modern HF radio sounding techniques: Doppler sounders (Menk et al 2007;Waters et al 2007;Pilipenko et al 2013) and SuperDARN HF radars (Lester et al 2000;Ponomarenko et al 2001;Teramoto et al 2014). The ever-growing array of global satellite navigation systems (GPS, GLONASS, etc.)…”

Section: Introductionmentioning

confidence: 99%

Modulation of the ionosphere by Pc5 waves observed simultaneously by GPS/TEC and EISCAT

et al. 2016

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Earlier studies demonstrated that the monitoring of the ionospheric total electron content (TEC) by global satellite navigation systems is a powerful method to study the propagation of transient disturbances in the ionosphere, induced by internal gravity waves. This technique has turned out to be sensitive enough to detect ionospheric signatures of magnetohydrodynamic waves as well. However, the effect of TEC modulation by ULF waves is not well examined as a responsible mechanism has not been firmly identified. During periods with intense Pc5 waves distinct pulsations with the same periodicity were found in the TEC data from high-latitude GPS receivers in Scandinavia. We analyze jointly responses in TEC variations and EISCAT ionospheric parameters to global Pc5 pulsations during the recovery phase of the strong magnetic storms on October 31, 2003. Comparison of periodic fluctuations of the electron density at different altitudes from EISCAT data shows that main contribution into TEC pulsations is provided by the lower ionosphere, up to ~150 km, that is the E-layer and lower F-layer. This observational fact favors the TEC modulation mechanism by field-aligned plasma transport induced by Alfven wave. Analytical estimates and numerical modeling support the effectiveness of this mechanism. Though the proposed hypothesis is basically consistent with the analyzed event, the correspondence between magnetic and ionospheric oscillations is not always perfect, so further studies need to be conducted to understand fully the TEC modulations associated with Pc5 pulsations.

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“…Other mechanisms also contributed. Waters et al (2007) have considered oblique propagation and have shown that the dominant mechanism for pulsations is the vertical E × B drift due to the pulsation field, which affects the path through the SP mechanism. A limitation of such observations is that the perturbation occurs in the ionosphere where the pulsation is located, while the radar measured the range of the ground.…”

Section: Determination Of Resonance Nature Of Eventsmentioning

confidence: 99%

Large-scale coordinated observations of Pc5 pulsation events

et al. 2016

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Abstract. HF (high-frequency) radars belonging to SuperDARN (Super Dual Auroral Radar Network) receive backscatter over substantial fields of view which, when combined, allow for simultaneous returns over extensive regions of the polar caps and midlatitudes. This makes them ideal instruments for the observation of pulsations in the Pc5 (1-5 mHz) frequency band. Relatively few pulsation events observed by multiple radars have been reported in the literature. Here we describe observations of three such events which extend over more than 120 • of magnetic longitude in the Northern Hemisphere and one of which is also detected in the Southern Hemisphere. All three events show characteristics of field line resonances. In one case the pulsation has also been observed by magnetometers under or near the radar fields of view. The extensive longitudinal coverage allows accurate determination of azimuthal wave numbers. These are at the upper end of the lower values associated with external sources such as those in the solar wind. Such sources imply antisunward flow. However, the azimuthal wave number is negative, implying westward propagation at magnetic local times on both sides of noon, as would be expected from drift-bounce resonance with positive particles. Quiet conditions and a very low ring current during the events argue against this. The identification of the source of pulsations from a number of different mechanisms remains a problem of interest.

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Modulation of radio frequency signals by ULF waves

Cited by 13 publications

References 46 publications

ULF wave effects on high frequency signal propagation through the ionosphere

ULF wave effects on high frequency signal propagation through the ionosphere

Modulation of the ionosphere by Pc5 waves observed simultaneously by GPS/TEC and EISCAT

Large-scale coordinated observations of Pc5 pulsation events

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