Links between mesopause temperatures and ground‐based VLF narrowband radio signals

Silber, Israel; Price, Colin; Rodger, Craig J.; Haldoupis, C.

doi:10.1002/jgrd.50379

Cited by 21 publications

(35 citation statements)

References 48 publications

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“…Because the D region's formation and chemistry are tightly bound to the neutral MLT (Brasseur and Solomon, 2005), it is believed that the D region is affected by the same forcings, experiencing similar oscillations (e.g., Schmitter, 2011;Silber et al, 2013;Marshall and Snively, 2014). As far as the current authors know, there are no previous works showing the SAO dominating the natural long-term oscillations in the nighttime D region apart from the work of Toledo-Redondo et al (2012), who presented a SAO indication within the equatorial latitudes by using space-based ELF-VLF data from the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) micro-satellite.…”

Section: Silber Et Al: Sao Of the Nighttime Ionospheric D Regionmentioning

confidence: 99%

“…At lower altitudes of the D region, where daytime VLF signals are reflected, we would expect chemical processes to dominate over NO dynamics, and therefore a very strong signature of solar insolation changes (which are seen mainly in the AO), together with relatively weak perturbations caused by other forcings and temperature changes, is observed (e.g., Schmitter, 2011;Silber et al, 2013). At higher altitudes within the D region, where nighttime VLF signals are reflected, dynamical processes are much more pronounced; thus oscillations, such as the SAO, which are driven by dynamical transport of important species as well as dynamical forcing (e.g., gravity and planetary waves) are much stronger and thus more easily detected.…”

Section: Region Ions and Dynamical Transport Of Neutral Speciesmentioning

confidence: 99%

“…A 60-day running-mean of the data was created, in order to obtain good local time coverage (Marsh et al, 2006). Only the SABER nighttime data (in a 1 • zonal-mean resolution) were examined, as the daytime and nighttime OH * airglow layers behave differently (Gao et al, 2015;Marsh et al, 2006;Smith, 2004). An examination of the 11-year (2002-2012) average peak emission is presented in Fig.…”

Section: The Vlf Sao Phase and Its Comparison With Satellite Datamentioning

confidence: 99%

“…Tides tend to break at ∼ 85 km (Lindzen, 1981) and like other large-scale atmospheric waves modify MLT temperatures by ∼ 5 K at midlatitudes (Marsh et al, 2006). In addition, tides are able to generate several kilometers of atmospheric species transport from above and below (Marsh et al, 2006;Smith, 2004). As was mentioned in the methodology section, we averaged a constant (localtime) hour in order to reduce the tidal effect, as it was not possible to average 24 h of VLF data due to the significant changes in the ionosphere between day and night.…”

Section: Tidal Effectsmentioning

confidence: 99%

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Semi-annual oscillation (SAO) of the nighttime ionospheric D region as detected through ground-based VLF receivers

2016

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Abstract. Earth's middle and upper atmosphere exhibits several dominant large-scale oscillations in many measured parameters. One of these oscillations is the semi-annual oscillation (SAO). The SAO can be detected in the ionospheric total electron content (TEC), the ionospheric transition height, the wind regime in the mesosphere-lower thermosphere (MLT), and in the MLT temperatures. In addition, as we report for the first time in this study, the SAO is among the most dominant oscillations in nighttime very low frequency (VLF) narrowband (NB) subionospheric measurements. As VLF signals are reflected off the ionospheric D region (at altitudes of ∼ 65 and ∼ 85 km, during the day and night, respectively), this implies that the upper part of the D region is experiencing this oscillation as well, through changes in the dominating electron or ion densities, or by changes in the electron collision frequency, recombination rates, and attachment rates, all of which could be driven by oscillatory MLT temperature changes. We conclude that the main source of the SAO in the nighttime D region is NO x molecule transport from the lower levels of the thermosphere, resulting in enhanced ionization and the creation of free electrons in the nighttime D region, thus modulating the SAO signature in VLF NB measurements. While the cause for the observed SAO is still a subject of debate, this oscillation should be taken into account when modeling the D region in general and VLF wave propagation in particular.

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Section: Silber Et Al: Sao Of the Nighttime Ionospheric D Regionmentioning

confidence: 99%

Section: Region Ions and Dynamical Transport Of Neutral Speciesmentioning

confidence: 99%

Section: The Vlf Sao Phase and Its Comparison With Satellite Datamentioning

confidence: 99%

Section: Tidal Effectsmentioning

confidence: 99%

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Semi-annual oscillation (SAO) of the nighttime ionospheric D region as detected through ground-based VLF receivers

2016

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“…The chemistry and formation of D-layer infer to be neutral environment and therefore, experience oscillations [12] [13]. To study this region was a tedious and difficult job till the discovery of remote sensing.…”

Section: Introductionmentioning

confidence: 99%

A Study on the VLF/LF Long Term Amplitude Oscillations Associated with Frequencies 37.5 kHz and 45.9 kHz Received at Keil Longwave Monitor, Keil, Germany

Sharma¹,

Kandel²,

Khadka³

et al. 2017

IJG

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The middle and upper atmosphere of Earth displays many large-scale oscillations in several parameters. Of these oscillations, Atmospheric Oscillation (AO) and Semi-annual Oscillation (SAO) are prominent ones. In this work, we have analyzed the Very Low Frequency/Low Frequency (VLF/LF) data from two of the transmitters of frequency 45.9 kHz at NSY, Sicily, Italy and 37.5 kHz at Grindavik, Iceland. The selected Trasmitter-Receiver Great Circle Path (TRGCP) is middle latitude which is marine in case of Grindavik TRGCP and terrestrial in case of NSY TRGCP. The VLF/LF signals are bounced back and forth from D-layer of ionosphere (altitude at ~65 km during day and ∼95 km during night) in Earth-ionospheric waveguide. This infers the presence of atmospheric oscillations as a consequence of change in ionization and recombination rates. Many works related to AO and SAO are mostly done only for equatorial region of the ionosphere and authors have reported the elegant dominancy of AO and SAO in the VLF/LF amplitude pattern over years. To our surprise, in our work it is seen that not only AO and SAO but also other oscillations are necessary to model the oscillation pattern of middle latitude ionosphere.

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Anomalously strong vertical magnetic fields from distant ELF/VLF sources

et al. 2015

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There are many sources of very low frequency (VLF—3–30 kHz) and extremely low frequency (ELF—3–3000 Hz) radiation in the Earth‐ionosphere waveguide (e.g., lightning and ELF/VLF communication transmitters). At distances of thousands of kilometers from these sources, the vertical component of the ELF/VLF AC magnetic fields is expected to be very weak and several orders of magnitude lower than the horizontal magnetic components. However, measurements in Israel show a relatively strong vertical magnetic component in both the ELF and VLF bands, at the same order of magnitude as the horizontal components. Our measurements suggest that the real Earth‐ionosphere waveguide might often be very different from the theoretical waveguide used in model calculations. In addition, our results imply that using only the horizontal components for direction finding or the absolute magnetic field strength may result in errors, since often a significant fraction of the magnetic field energy hides in the vertical component.

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Links between mesopause temperatures and ground‐based VLF narrowband radio signals

Cited by 21 publications

References 48 publications

Semi-annual oscillation (SAO) of the nighttime ionospheric D region as detected through ground-based VLF receivers

Semi-annual oscillation (SAO) of the nighttime ionospheric D region as detected through ground-based VLF receivers

A Study on the VLF/LF Long Term Amplitude Oscillations Associated with Frequencies 37.5 kHz and 45.9 kHz Received at Keil Longwave Monitor, Keil, Germany

Anomalously strong vertical magnetic fields from distant ELF/VLF sources

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