Possible Clues:

• The Kennelly-Heaviside layer lies within the earth’s ____
• Sky region broadcast poison at this point
• Where to find Appleton and Heaviside layers, i.e. poor hens in poor state
• Poison spreading in this location, a distant region
• Sky region's broadcast poison in this place
• Heavenly reflector of radio waves
• Where the D layer is
• Terrible poison present in this gaseous envelope?
• Layer reflecting radio waves
• Where the Northern Lights occur