IONOSPHERIC EFFECTS DUE TO ELECTROSTATIC THUNDERCLOUD FIELDS

Electrostatic thundercloud fields are shown to heat lower ionospheric electrons significantly under night time conditions. The effect is max imized under conditions of higher altitudes of thundercloud charges, l arger magnitudes of these charges, and larger scale heights of ambient conductivity profiles. The lower ionospheric conductivity can be modi fied as a result of the heating by up to one order of magnitude in reg ions with a characteristic lateral extent of similar to 150 to 350 km. The vertical extent of the heated region is similar to 10 km, at alti tudes of similar to 70-80 km, reaching above 85 km in some cases, depe nding on the ambient night-time conductivity profile. The electron hea ting may potentially alter the chemical balance in the D-region, modif y the ambient levels of optical emissions and the magnitude of electro static thundercloud fields which map to higher ionospheric altitudes. (C) 1998 Elsevier Science Ltd. All rights reserved.