D-layer


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Synonyms for D-layer

the lowest region of the ionosphere (35 to 50 miles up) that reflects low-frequency radio waves

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References in periodicals archive ?
[11] proposed (29), useful to calculate the absorption due to the propagation across the ionospheric D-layer, which can be approximately modelled by a linearized complex refractive index (25a), (25b), covering a short range of heights between [h.sub.1] = 50 km and [h.sub.2] = 80-90 km approximately.
Just the reasonable hypothesis assumed below equations (30a)-(30b) could imply the expected conclusions for (30a)(30b); the real refractive index [n.sub.R](h) is a decreasing function of height h, while the imaginary refractive index n- is negative, as substantially correct for any ionospheric profile of the D-layer [4].
Figure 2 compares two profiles of electron density modelling the ionospheric D-layer between the heights [h.sub.1] and [h.sub.2] > [h.sub.1]; the first profile agrees with the linearized complex refractive index (31a)-(31b), and is defined by a lower limit ([h.sub.0], [N.sub.0]), such that [h.sub.0] < [h.sub.1], while the second profile responds to Chapman's (19) and is specified by a relative maximum ([h.sub.max], [N.sub.max]), such that [h.sub.max] > [h.sub.2].
The D-layer, represented by a complex eikonal model, covers a short range of heights between [h.sub.1] = 50 km and [h.sub.2] = 80-90 km, the absolute temperature decreasing, respectively, from [T.sub.1] = 273 K to [T.sub.2] = 187 K 3].
Indeed, as proved, the D-layer is generally more carefully defined by the Settimi et al.
With the Sun absent at night, the D-layer vanishes; signal strength varies randomly and can often be quite high.