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 maximized under conditions of higher altitudes of thundercloud charges, larger magnitudes of these charges, and larger scale heights of ambient conductivity profiles. The lower ionospheric conductivity can be modified as a result of the heating by up to one order of magnitude in regions with a characteristic lateral extent of ~150 to 350 km. The vertical extent of the heated region is ~10 km, at altitudes of ~70-80 km, reaching above 85 km in some cases, depending on the ambient night-time conductivity profile. The electron heating may potentially alter the chemical balance in the D-region, modify the ambient levels of optical emissions and the magnitude of electrostatic thundercloud fields which map to higher ionospheric altitudes.