Physics
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufmsm13a1662h&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #SM13A-1662
Physics
2415 Equatorial Ionosphere, 2730 Magnetosphere: Inner, 2736 Magnetosphere/Ionosphere Interactions (2431), 2790 Substorms
Scientific paper
At the onset of magnetospheric substorms, impulsive hydromagnetic oscillations with periods of 40-150 sec, so called Pi 2 magnetic pulsations, occur globally in the magnetosphere. Pi 2 pulsations have been researched for a long time. However, equatorial Pi 2 pulsations have not been analyzed sufficiently and in the most of past studies only H-component of equatorial Pi 2 pulsations were examined. In our previous study, we analyzed H-component magnetic data obtained from MAGDAS/CPMN stations, AAB(G.long.=38.77), LKW(99.78), CEB(123.91), DAV(125.40), YAP(138.08), ANC(-77.15) and EUS(-38.43) which are located near the dip equator. We found that enhancement of H-component wave amplitude of Pi 2 pulsations are occurred near the daytime dip equator. Furthermore, by comparing the data obtained from CEB, DAV and YAP, we also found that as the observation site is nearer to the dip equator, the Pi 2 amplitudes tended to become larger. This amplitude enhancement of Pi 2 pulsations was seen not only in daytime but also in nighttime. We could explain the enhancement in daytime as effect of equatorial electrojet, but we had no idea to explain the enhancement in nighttime. In the present study, we analyze H, D and Z-component wave amplitudes of equatorial Pi 2 pulsations obtained from CEB, DAV and ANC stations for the period of January 1-31, March 1~31 and Jun 1~30 2005. The following new results are obtained; (1) Amplitude ratio of H-component of equatorial Pi 2s at DAV (Dip Lat =-0.65) to CEB (2.73) is found to be almost 1.5 in nighttime, while that in daytime to show the equatorial enhancement and a monthly dependence. (2) Amplitude ratio of D-component to H-component of equatorial Pi 2 are found to be almost 0.3, in particularly to enhance to 0.5 at near local sunrise and sunset time, while H-component equatorial Pi 2 amplitude decrease at sunrise and sunset time. (3) Amplitude ratio of Z-component to H-component of equatorial Pi 2 are found to be 0.3 at CEB and ANC, and 0.1 at DAV respectively. The amplitude ratio of H-component Pi 2s at DAV to CEB is found to be almost 1.5 constantly in night in all season, indicating the CA effect of equatorial Pi 2. The enhancement of the ratio of D-component to H- component at around sunrise and sunset may be explained by the meridional ionospheric current of equatorial Pi 2, but more future study is needed. Acknowledgements We appreciate the following Co-investigators for their contribution to the MAGDAS/CPMN project; Dr. Baylie Damtie(Bahir Dar University, AAB), Dr. Ronald Woodman Pollitt and Dr. Jose Ishitsuka (Instituto Geofisico del Peru, ANC), Dr. Roland Emerito S. Otadoy(University of San Carlos, CEB), Fr. Daniel McNamara(Manila Observatory, DAV), Dr. Severino L. G. Dutra(Brazilian National Space Research Institute, EUS) and Dr. Mazlan Othman and Dr. Mohd Fairos (National Space Agency, LKW). We appreciate Dr. Shinichi Watari(National Institute of Information and Communications Technology) providing the magnetic field data of YAP.
Group M.
Hirayama Yoshiharu
Uozumi Teiji
Yoshikawa Akira
Yumoto Kiyo
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