HR: 10:35h
AN: SM22A-02 [Abstracts]
TI: Low-latitude ELF Whistler-like Events Observed in Taiwan
AU: * Wang, K
EM: ktwang@must.edu.tw
AF: Division of Natural Sciences, Ming Hsin University of Science and Technology, 1 Hsin Hsing Rd, Sin Fong,
Hsin Chu, 304
Taiwan
AU: Wang, Y
EM: l2890102@phys.ncku.edu.tw
AF: Department of Physics, National Cheng Kung University, 1 Da-Hsueh Rd., Tainan, 700
Taiwan
AU: Hsu, R
EM: rrhsu@phys.ncku.edu.tw
AF: Department of Physics, National Cheng Kung University, 1 Da-Hsueh Rd., Tainan, 700
Taiwan
AU: Su, H
EM: htsu@phys.ncku.edu.tw
AF: Department of Physics, National Cheng Kung University, 1 Da-Hsueh Rd., Tainan, 700
Taiwan
AU: Lee, L
EM: loulee@narl.org.tw
AF: Department of Physics, National Cheng Kung University, 1 Da-Hsueh Rd., Tainan, 700
Taiwan
AU: Lee, L
EM: loulee@narl.org.tw
AF: National Applied Research Laboratories, 3F, 106 Hoping E. Rd. Sec2, Taipei, 106
Taiwan
AB:
Whistler-like events between 60 to 100 Hz have been detected in the ELF station operated by NCKU-ISUAL team at the Lulin
Observatory, Taiwan (120$^{o}$52'E, 23$^{o}$28' N, 2862m high) from August 20, 2003 to July 29, 2004. The most distinguished
feature is the frequency descent in the frequency-time spectrograms, resembling terrestrial whistlers. Other features of the
ELF events include(a) a long event duration up to 2 minutes, (b) a daytime diurnal maximum occurring around 10 am, (c) a
dominant magnetic field polarization in the north-south direction with strength at a few to tens of pT, and (d) no detection
of vertical electric fields...etc.
For the past 20 years, similar events were only reported twice, one at the auroral latitude (Heacock, 1974) and the other
at the mid-latitude (Sentman and Ehring, 1994). Possible source mechanisms have been discussed are (a) magenetosheath lion
roars propagating along the TEM-mode waveguide in the earth-ionosphere cavity, and (b) hiss detected in the equator.
Lightning-generated whistlers are not favored in previous studies because of being unable to interpret the observed long
dispersions with the electron density environment but all the mechanisms remain open questions.
References
Heacock, R.R., Whistler-like pulsation events in the frequency range 20-200Hz,$\em Geophys. Res. Lett.$, 2, 77, 1974.
Sentman, D. D., D. A. Ehring, Midlatitude detection of ELF whistlers.$\em J. Geophys. Res.$, 99, 2183, 1994.
DE: 7871 Waves and instabilities
DE: 7894 Instruments and techniques
DE: 7899 General or miscellaneous
DE: 6964 Radio wave propagation
DE: 6984 Waves in plasma
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting