Individual #Appleton_layer__F_layer__F_region  the highest region of the ionosphere (from 90 to 600 miles up) that contains the highest concentration of free electrons and is most useful for long-range radio transmission
  part of:  ionosphere
  type:  region.location__part  the extended spatial location of something; "the farming regions of France"; "religions in all parts of the world"; "regions of outer space"

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