TY - JOUR
T1 - Preseismic alteration of atmospheric electrical conditions due to anomalous radon emanation
AU - Omori, Yasutaka
AU - Nagahama, Hiroyuki
AU - Kawada, Yusuke
AU - Yasuoka, Yumi
AU - Ishikawa, Tetsuo
AU - Tokonami, Shinji
AU - Shinogi, Masaki
N1 - Funding Information:
The authors would like to thank M. Hayakawa, P.F. Biagi, K. Hattori, O.A. Molchanov, C.-V. Meister and B.A. Tinsley for valuable comments, D. Nair for revising the English style of this manuscript, and two anonymous reviewers for critical reviews. This study was conducted as a part of the 21st Century Center-Of-Excellence program, “Advanced Science and Technology Center for the Dynamic Earth”, of Tohoku University. Y. Omori acknowledges financial help from the Support Program Graduate School Education by Graduate School of Science, Tohoku University. Y. Kawada was supported by the JSPS Research Fellowship for Young Scientists and is by the JSPS Postdoctoral Fellowship for Research Abroad.
PY - 2009
Y1 - 2009
N2 - Preseismic radon (Rn-222) emanation is considered to be one of the main physical mechanisms of electromagnetic precursory phenomena. In this paper, we analyze the atmospheric radon concentration around the occurrence time of the 1995 Kobe earthquake, and evaluate the influence on the atmospheric electrical conditions based on the global electric circuit under the quasistatic state. The radon emanation increases the number density of small ions and the atmospheric conductivity and decreases the atmospheric electric field by about 40-50% in the lower atmosphere, while they show little change in the upper atmosphere. The difference in the lower and upper atmosphere induces the reduction of the ionospheric potential. The estimated quasistatic changes near the ground can explain the reported seismic precursors such as the ion number density and the electric field. At the ionospheric altitude, however, not only the quasistatic process but also the shorter-term process, i.e., a transient electrodynamic process in the atmosphere is required for the understanding of the lithosphere-atmosphere-ionosphere interaction due to the radon emanation associated with large earthquakes.
AB - Preseismic radon (Rn-222) emanation is considered to be one of the main physical mechanisms of electromagnetic precursory phenomena. In this paper, we analyze the atmospheric radon concentration around the occurrence time of the 1995 Kobe earthquake, and evaluate the influence on the atmospheric electrical conditions based on the global electric circuit under the quasistatic state. The radon emanation increases the number density of small ions and the atmospheric conductivity and decreases the atmospheric electric field by about 40-50% in the lower atmosphere, while they show little change in the upper atmosphere. The difference in the lower and upper atmosphere induces the reduction of the ionospheric potential. The estimated quasistatic changes near the ground can explain the reported seismic precursors such as the ion number density and the electric field. At the ionospheric altitude, however, not only the quasistatic process but also the shorter-term process, i.e., a transient electrodynamic process in the atmosphere is required for the understanding of the lithosphere-atmosphere-ionosphere interaction due to the radon emanation associated with large earthquakes.
KW - Atmospheric radon concentration
KW - Earthquake
KW - Electric circuit system
KW - Electric field
KW - Ionosphere
KW - Small ion
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U2 - 10.1016/j.pce.2008.08.001
DO - 10.1016/j.pce.2008.08.001
M3 - Article
AN - SCOPUS:62549159572
SN - 1474-7065
VL - 34
SP - 435
EP - 440
JO - Physics and Chemistry of the Earth
JF - Physics and Chemistry of the Earth
IS - 6-7
ER -