HR: 1340h
AN: AE23A-0910    [Abstracts]
TI: Estimated intensity of the EMP from lightning discharges necessary for elves initiation based on balloon experiment
AU: * Kondo, S
EM: kondo@pat.geophys.tohoku.ac.jp
AF: Department of Geophysics, Tohoku University, Aramaki-aoba, Aoba-ku, Sendai, 980-8578, Japan
AU: Yoshida, A
EM: akihiro@pat.geophys.tohoku.ac.jp
AF: Department of Geophysics, Tohoku University, Aramaki-aoba, Aoba-ku, Sendai, 980-8578, Japan
AU: Takahashi, Y
EM: yukihiro@pat.geophys.tohoku.ac.jp
AF: Department of Geophysics, Tohoku University, Aramaki-aoba, Aoba-ku, Sendai, 980-8578, Japan
AU: Chikada, S
EM: chikada@pat.geophys.tohoku.ac.jp
AF: Department of Geophysics, Tohoku University, Aramaki-aoba, Aoba-ku, Sendai, 980-8578, Japan
AU: Adachi, T
EM: adachi@pat.geophys.tohoku.ac.jp
AF: Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, 611- 0011, Japan
AU: Sakanoi, T
EM: tsakanoi@pparc.geophys.tohoku.ac.jp
AF: Department of Geophysics, Tohoku University, Aramaki-aoba, Aoba-ku, Sendai, 980-8578, Japan
AB: Transient optical phenomena in the mesosphere and lower ionosphere called transient luminous events (TLEs) have been investigated extensively since the first discovery in 1989. In the lower ionosphere, elves are generated by the electromagnetic pulses (EMPs) radiated from the intense lightning current. On the ground-based observation, cameras can not always identify the occurrence of elves because elves emission is sometimes reduced significantly by the atmosphere and blocked by clouds. Therefore, it has been difficult to determine the threshold of intensity of EMPs necessary for initiation of elves. We simultaneously carried out optical and sferics measurements for TLEs and lightning discharges using a high altitude balloon launched at Sanriku Balloon Center on the night of August 25 / 26 in 2006. We fixed four CCD cameras on the gondola, each of which had horizontal FOV of ~100 degree. They cover 360 degree in horizontal direction and imaged the TLEs without atmospheric extinction nor blocking by clouds. The frame rate is 30 fps. We installed three dipole antennas at the gondola, which received the vertical and horizontal electric fields radiated from lightning discharges. The frequency range of the VLF receiver is 1-25 kHz. We also make use of VLF sferics data obtained by ground-based antennas located at Tohoku University in Sendai. We picked up six elves from the image data set obtained by the CCD cameras, and examined the maximum amplitudes of the vertical electric field for 22 lightning discharge events including the six elves events observed both at the balloon and at Sendai. It is found that the maximum amplitudes of the vertical electric field in the five elves events are much larger than those in the other lightning events. We estimate the intensity of the radiated electric field necessary for elves. About one elves event, we donft see intense vertical electric field in the balloon data.
DE: 3304 Atmospheric electricity
DE: 3324 Lightning
SC: Atmospheric and Space Electricity [AE]
MN: 2007 Fall Meeting