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A layer of the ionosphere able to reflect medium-frequency radio waves.‘The effect of the Ampére force on inertio-gravity (IG) waves in the partially ionized ionospheric E-layer is considered.’‘At the fully-developed stage, the fully-extended luminous body connected the cloud top at 15km with the E-layer ionosphere at 90km.’
1930s arbitrary use of the letter E, + layer.
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