*the ‘D layer’ is the ‘innermost layer’, 60 km (37 mi) to 90 km (56 mi) above the surface of the ‘earth’*
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(‘ionization’ here is due to Lyman series-alpha hydrogen radiation at a wavelength of 121.6 nanometre (nm) ionizing nitric oxide (NO))
(in addition, high solar activity can generate hard X-rays (wavelength < 1 nm) that ionize N2 and O2)
(‘recombination rates’ are high in the ‘D layer’, so there are many more ‘neutral air molecules’ than ‘ions’)
(‘medium frequency’ (MF) and ‘lower high frequency’ (HF) radio waves are significantly attenuated within the ‘D layer’, as the passing ‘radio waves’ cause ‘electrons’ to move, which then collide with the ‘neutral molecules’, giving up their ‘energy’)
(lower frequencies experience greater absorption because they move the electrons farther, leading to greater chance of collisions)
(this is the main reason for absorption of ‘HF radio waves’, particularly at 10 MHz and below, with progressively less absorption at higher frequencies)
(this effect peaks around noon and is reduced at night due to a decrease in the D layer’s thickness; only a small part remains due to ‘cosmic rays’)
(a common example of the ‘D layer’ in action is the disappearance of distant AM broadcast band stations in the ‘daytime’)
(during ‘solar proton events’, ‘ionization can reach unusually high levels in the ‘D-region’ over high and polar latitudes)
(such very rare events are known as ‘Polar Cap Absorption’ (or PCA) events, because the increased ‘ionization’ significantly enhances the absorption of radio signals passing through the region)
(in fact, absorption levels can increase by many tens of dB during intense events, which is enough to absorb most (if not all) transpolar HF radio signal transmissions)
(such events typically last less than ’24’ to ’48’ hours)
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*👨🔬🕵️♀️🙇♀️*SKETCHES*🙇♂️👩🔬🕵️♂️*
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👈👈👈☜*“THE 4 LAYERS OF EARTH’S IONO-SPHERE”* ☞ 👉👉👉
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💕💝💖💓🖤💙🖤💙🖤💙🖤❤️💚💛🧡❣️💞💔💘❣️🧡💛💚❤️🖤💜🖤💙🖤💙🖤💗💖💝💘
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*🌈✨ *TABLE OF CONTENTS* ✨🌷*
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🔥🔥🔥🔥🔥🔥*we won the war* 🔥🔥🔥🔥🔥🔥