#ionosphere  the outer region of the Earth's atmosphere; contains a high concentration of free electrons
  supertype:  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"
  part of:  atmosphere
  part:  D-layer__D_region  the lowest region of the ionosphere (35 to 50 miles up) that reflects low-frequency radio waves
  part:  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:  Kennelly-Heaviside_layer__Heaviside_layer__E_layer__E_region  a region of the ionosphere (from 50 to 90 miles up) that reflects radio waves of medium length

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