Property of parent lightning discharges of elves

Elves are optical flashes in the lower ionosphere caused by electro-magnetic pulses (EMP) radiated from lightning discharges, nowadays, being observed by the FORMOSAT-2/ISUAL from the space. More than 3000 elve events have been observed from July 2004 to July 2006. In addition to it, we observe radio waveforms radiated from lightning discharges at the range of ELF (1-100 Hz) and VLF (1k-40k Hz) to obtain characteristics of parent lightning discharges and to distinguish lightning events into Cloud-to-Ground (CG) and Intra-Cloud (IC) lightning. We have investigated the seasonal dependent distribution map of elves observed from July 2004 to June 2005. It is different from that of lightning activity obtained by the OTD instrument. Especially, remarkable point is that continental lightning are more active than oceanic lightning, however, most of elves have occurred over the ocean. In order to investigate a characteristic of lightning inducing elve, we distinguished 22 lightning events observed near the Onagawa observatory into 6 CGs and 16 ICs from ELF data. Then, the ratio of the ISUAL AP data, which we define as AP blue divided by AP red, have maximum value at the initial stage of emission of lightning for the CG case and the decaying stage for the IC case. This result enables us to distinguish almost all lightning events into CG/IC and to investigate requirement for occurrence of elve. We expect that a property of lightning contributing for elve generation is time constant which means fast discharges can radiate intense EMP. So, we will estimate the maximum EMP values from time-derivation of SP or AP data. Here, we assume that current time series is consistent with the emission of lightning. In this presentation, we will suggest the relation between maximum EMP value of parent lightning discharges and elve generation.