Other
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufmsa21b0347t&link_type=abstract
American Geophysical Union, Fall Meeting 2004, abstract #SA21B-0347
Other
2427 Ionosphere/Atmosphere Interactions (0335), 2431 Ionosphere/Magnetosphere Interactions (2736), 2435 Ionospheric Disturbances, 2437 Ionospheric Dynamics, 2443 Midlatitude Ionosphere
Scientific paper
The interhemispheric conjugacy of large-scale traveling ionospheric disturbances (LSTIDs) was studied using total electron content (TEC) data derived from GPS networks in Japan and Australia. LSTIDs are generally believed as the ionospheric manifestations of the passage of atmospheric gravity waves (AGWs) that are generated at high latitudes by the energy input from the magnetosphere. Although this energy is considered to be injected into both hemispheres coincidently, there have been few studies focusing on the geomagnetic conjugacy of LSTIDs by observations using GPS networks in both hemispheres. Thirty-eight LSTIDs were identified in 2002 using two-dimensional TEC maps derived from GEONET, a dense and wide-area GPS network in Japan. All the LSTIDs propagated southward over Japan. We sought southern hemispheric LSTIDs within about an hour of the appearance of each northern hemispheric LSTID using several GPS receivers in Australia. The number of conjugate occurrence of LSTIDs was five that is 25% of all the LSTIDs observed in the north hemisphere when Kp≥5-. There is no conjugate occurrences when Kp≤4+. This indicates that the conjugate occurrence of LSTIDs is infrequent even though the geomagnetic activity is large. Detail comparison of TEC variations over Japan to those over the geomagnetic conjugate region revealed that the passage times of conjugate LSTIDs were not precisely simultaneous but different by several tens of minutes for all the five events. The meridional propagation velocities of conjugate LSTIDs were also different by several hundreds of m/s. The faster LSTIDs in one hemisphere tend to be found earlier at the conjugate regions than the slower LSTIDs in the other hemisphere. These observational results indicate that LSTIDs propagating simultaneously in both hemispheres have no electromagnetic connection through the geomagnetic field between each other. This study revealed that there is little interhemispheric conjugacy on the property of the occurrences and propagations of LSTIDs.
Nishioka Masaya
Ogawa Takuro
Otsuka Yoichi
Saito Akiko
Shiokawa Kazuhiko
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