Relationship between tropospheric processes and the midlatitude absorption of cosmic radio emission

Observations made at the Borok midlatitude observatory are examined. It is shown that a riometric-absorption bay arises and VLF-emission intensity increases during sharp large-amplitude variations of the vertical atmospheric electric field, accompanied by a pressure jump. An analysis of 70 events with allowance for geomagnetic disturbances leads to the conclusion that the ionospheric disturbances are caused by tropospheric processes. Possible mechanisms for the tropospheric effect on the ionosphere are examined, including the penetration of tropospheric electric fields into the ionosphere, electron precipitation due to the interaction between VLF emission and high-energy electrons, and the refraction of cosmic radio waves by ionospheric irregularites.