Seasonal variation in the asymmetry of diurnal variation of absorption in the lower ionosphere

Laštovička, Jan

doi:10.1016/0021-9169(77)90169-6

Cited by 24 publications

(6 citation statements)

References 4 publications

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“…This asymmetry was observed for SZAs greater than 80 • and in an altitude region between 75 and 95 km. Other studies using MF radar (Coyne and Belrose, 1972;Laštovička, 1977;Li and Chen, 2014, e.g. ) and VLF observations (e.g.…”

Section: Discussionmentioning

confidence: 98%

“…The D-region sunset-sunrise asymmetry is a phenomenon that has been studied for several decades with various tech-niques. The asymmetry is usually characterized by MF radars measuring the transmitted wave's Faraday rotation (Coyne and Belrose, 1972) and by oblique radio link amplitudes at different MF frequencies (Laštovička, 1977). We report the first direct measurements of the D-region electron density asymmetry by calibrated incoherent-scatter radar observations.…”

Section: Discussionmentioning

confidence: 99%

“…Other methods including MF radar (e.g Coyne and Belrose, 1972;Li and Chen, 2014) and radio propagation methods (e.g. Laštovička, 1977) have also been used to investigate the D region during these times and discovered an asymmetry in the observed electron densities.…”

Section: Introductionmentioning

confidence: 99%

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Arecibo measurements of D-region electron densities during sunset and sunrise: implications for atmospheric composition

Baumann

Kero²,

Raizada

et al. 2022

Ann. Geophys.

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Abstract. Earth's lower ionosphere is the region where terrestrial weather and space weather come together. Here, between 60 and 100 km altitude, solar radiation governs the diurnal cycle of the ionized species. This altitude range is also the place where nanometre-sized dust particles, recondensed from ablated meteoric material, exist and interact with free electrons and ions of the ionosphere. This study reports electron density measurements from the Arecibo incoherent-scatter radar being performed during sunset and sunrise conditions. An asymmetry of the electron density is observed, with higher electron density during sunset than during sunrise. This asymmetry extends from solar zenith angles (SZAs) of 80 to 100∘. This D-region asymmetry can be observed between 95 and 75 km altitude. The electron density observations are compared to the one-dimensional Sodankylä Ion and Neutral Chemistry (SIC) model and a variant of the Whole Atmosphere Community Climate Model incorporating a subset SIC's ion chemistry (WACCM-D). Both models also show a D-region sunrise–sunset asymmetry. However, WACCM-D compares slightly better to the observations than SIC, especially during sunset, when the electron density gradually fades away. An investigation of the electron density continuity equation reveals a higher electron–ion recombination rate than the fading ionization rate during sunset. The recombination reactions are not fast enough to closely match the fading ionization rate during sunset, resulting in excess electron density. At lower altitudes electron attachment to neutrals and their detachment from negative ions play a significant role in the asymmetry as well. A comparison of a specific SIC version incorporating meteoric smoke particles (MSPs) to the observations revealed no sudden changes in electron density as predicted by the model. However, the expected electron density jump (drop) during sunrise (sunset) occurs at 100∘ SZA when the radar signal is close to the noise floor, making a clear falsification of MSPs' influence on the D region impossible.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

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Arecibo measurements of D-region electron densities during sunset and sunrise: implications for atmospheric composition

Baumann

Kero²,

Raizada

et al. 2022

Ann. Geophys.

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“…However, ionospheric absorption-which originates in the D-region (or mesosphere)-has long been known to be consistently larger in the afternoon than in the morning for the same solar zenith angles (Laštovička 1977). Since the lifetime of free electrons is much too short to explain this difference the ionisation has to be different between forenoon and afternoon.…”

Section: Regular and Irregular Variationsmentioning

confidence: 99%

News from the Lower Ionosphere: A Review of Recent Developments

Friedrich

Rapp

2009

Surv Geophys

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Current knowledge concerning the lower ionosphere (D-and E-region) is reviewed with an emphasis on new aspects of empirical results. Starting with an overview of experimental techniques and corresponding data bases, both regarding charged as well as the most relevant neutral constituents of this altitude range, the ionospheric variability is discussed both concerning regular (e.g. diurnal and seasonal) as well as irregular variations (e.g. driven by the variability of nitric oxide). We then turn to 'new players' in the lower ionosphere, i.e. charged aerosol particles such as mesospheric ice particles in noctilucent clouds or polar mesospheric summer echoes and meteor smoke particles originating from ablated meteoric matter. These species have received considerable attention in recent years, in part because it is speculated that observations of their properties might be useful for the detection of climate change signals. The available experimental data base regarding these species is reviewed and we show that there is now compelling evidence for the ubiquitous presence of these very heavy charge carriers throughout the lower ionosphere. While many fundamental details regarding these charged species are not yet completely understood, this emphasizes that charged aerosol particles may not be neglected in a comprehensive treatment of the lower ionospheric charge balance and related phenomena. Finally, we close with suggestions for future research.

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“…However, inserting sunrise and sunset [NO] in a theoretical model ofthe lower ionosphere resulted in electron densities very much resembling a.m./p.m. differences that had been known for decades in the ionospheric community from the measurements of radiowave absorption [32][33]. This ionospheric support of the novel satellite data eventually led theoreticians to come forth with tidal explanations of this behavior, which had not been anticipated by atmospheric scientists [34][35].…”

Section: Applications Of Lower-ionosphere Data/modelsmentioning

confidence: 98%

The lower ionosphere: Abandoned by communication, to be re-discovered for aeronomy

Friedrich¹

2004

URSI Radio Sci. Bull.

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The point is made that research on the lower ionosphere is still of importance, despite the decline in interest for communication. Today, the emphasis must be on the space weather aspect, and on the fact that ionospheric research provides important supporting information for atmospheric science, including global change investigations. Examples of ionospheric evidence are presented that are of potential interest to atmospheric scientists, who may not aware of such data.Editors note: This is one of the invited Reviews ofRadio Science, from Commission G.

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Seasonal variation in the asymmetry of diurnal variation of absorption in the lower ionosphere

Cited by 24 publications

References 4 publications

Arecibo measurements of D-region electron densities during sunset and sunrise: implications for atmospheric composition

Arecibo measurements of D-region electron densities during sunset and sunrise: implications for atmospheric composition

News from the Lower Ionosphere: A Review of Recent Developments

The lower ionosphere: Abandoned by communication, to be re-discovered for aeronomy

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