Interaction of up going ion beam forming current flow in the pre-ionized stepped leader plasma and the way, how the kinetic energy of the beam particles is converted into electromagnetic energy have been discussed. The ion beam interaction with the plasma wave modes in the stepped leader channel produces perturbations in the return stroke current flow and changes its uniformity and becomes non-uniform. In the present study, the return current is taken to be deeply modulated at a given modulation frequency, and considered that it behaves like an antenna for electromagnetic radiation. In this paper the total amount of energy associated with return stroke is given to electromagnetic waves is estimated. I. Introduction Lightning return stroke is an up going ion beam within a pre-ionized channel called stepped leader in which the excessive electrons deposited during the leader process are drained to the earth. The partially ionized stepped leader channel is supposed to bring the negative charge from the cloud base and distributes it homogeneously along the channel. The front of the return stroke moves upward with the velocity near to the velocity of light in the partially ionized channel (1 - 6). The electromagnetic energy radiated by lightning return stroke covers a wide frequency range, extending from a few hertz in the ELF band to the visible light (7 - 11). The exact physical processes, due to which radiation of electromagnetic waves from the ionized channel, taking place is not known clearly. The current in the channel is the main cause of electromagnetic radiation. The approximate assumption of the simple harmonic form of return current flow in the pre-ionized channel of stepped leader largely governs the radiated electromagnetic power and its spectral characteristics (12 - 13). The double exponential form of return current flow does explain certain features of atmospherics but it is not based on the plasma processes taking place in the return stroke current flow in the lightning channel. Singh and Singh (13) have reported in their presentation that the upwelling ion beam interacts with the pre-ionized channel and gives rise to resulting return current. The resulting current in the lightning channel may become an oscillatory as a result of plasma wave interaction. The energy extraction from upwelling ion beam requires, for emission of the electromagnetic waves, that the phase matching between waves and particles should be maintained for as long as possible. This desirable property is maintained by Cernkov and Cyclotron resonances. In this presentation, the idea of modulated current which flows into the pre-ionized plasma channel is taken (14 - 16) and is applied to the electromagnetic emission from the ion beam forming the return stroke. For this study it is considered that the modulated beam behaves like an antenna for the electromagnetic radiation. The value of modulation frequency, Ω is chosen such that force resonance condition (i.e. ω = ± Ω) may be sustained (ω = + ω for Cernkov resonance, and ω = - Ω for cyclotron resonance). In this presentation it has been reported that the electromagnetic power as a form of ion whistler Anomalous Doppler Shifted (ADS) mode is radiated from lightning return stroke channel. The energy in an ion whistler ADS mode is mainly due to the oscillatory damping of lower and upper wave modes in the stepped leader channel (10). The electromagnetic radiation from an oscillatory current source becomes variable. Such variations in recorded whistler are often observed in whistler sonograms. This paper is organized as follows: In sec. (II) return stroke ion beam interaction with pre-ionized stepped leader is discussed. Sec. (III) is devoted to describe the beam model on the basis of subsequent considerations. In sec. (IV) expression of electromagnetic power for ion whistler ADS mode is carried out. In sec. (V) applications of our proposal and its validity are argued. Results are presented and discussed in this section of the study. Finally, sec. (VI) states the conclusions.