Heating and ionization processes to lower ionosphere by lightning induced electromagnetic waves

In this thesis, it is investigated heating and ionization of the nighttime lower ionosphere by electromagnetic radiation in the VLF (Very Low Frequency) band that transmitted by cloud-to-ground (CG) lightning return stroke. For this purpose, temperature of electrons in the lower ionosphere is calculated by electron energy balance equation that obtained by using Maxwellian distribution. The effect of the Earth?s magnetic field is also used in calculations and seen that the magnetic field allocated the lightning-induced EM wave to different modes. It is observed that all these EM wave modes increase significantly to electron temperature of lower ionosphere in proportion to the electrical field. In the 10 V/m of the electrical field for all modes, it is seen that electron temperature increased about by 9000-11000 oK. These temperatures reached an altitude of about 85-90 km. With the increase of the electric field, it is seen that the altitude where reached maximum temperature values shifted upward. The Right-Handed mode of EM wave seen continued to progress without lose the effect to 95-100 km altitude as other modes. Lightning induced ionization is calculated by using a simple four-component model of lower ionosphere. However, two-body attachment reaction which neglected in previous studies and associative detachment of active species reaction which effected especially above 72 km altitude are included to this model. In the result of calculations, three-body attachment process between the 50-72 km altitude, associative detachment process between about 72-85 km altitude and two-body attachment process between about 85-95 km altitude on the electron density were observed to be effective. It seen that attachment of active species not depend very much on the value of applied electric field. In contrast, it observed that two-body attachment of electrons depend sharply on values of applied electric field. Moreover, for the values of electric field used in this study, because of to be much ionization by interaction time with lower ionosphere of EM wave, it is found that perturbed value of electron density greater than by 5.5 times from its not perturbed value. Key Words: Lightning, Lower Ionosphere, EM Waves, Heating and Ionization