TY - JOUR

T1 - Analysis of propagation delays of compressional Pi 2 waves between geosynchronous altitude and low latitudes

AU - Imajo, Shun

AU - Yumoto, Kiyohumi

AU - Uozumi, Teiji

AU - Kawano, Hideaki

AU - Abe, Shuji

AU - Ikeda, Akihiro

AU - Koga, Kiyokazu

AU - Matsumoto, Haruhisa

AU - Obara, Takahiro

AU - Marshall, Richard

AU - Akulichev, Victor A.

AU - Mahrous, Ayman

AU - Liedloff, Adam

AU - Yoshikawa, Akimasa

N1 - Funding Information:
This work was supported by the JSPS Core-to-Core Program, B. Asia-Africa Science Platforms. MAGDAS magnetic data from MUT and YAP are supported by Mr. Commodore Romeo I. Ho and Dr. David Aranug, respectively. The Honolulu magnetic field data were provided by the USGS Geomagnetism Program. Kp-index data was provided by the World Data Center for Geomagnetism, Kyoto, Website. Financial support was provided by the Ministry of Education, Science and Culture of Japan in the form of Grants-in-Aid for Overseas Scientific Survey (18253005 and 22253007).

PY - 2014

Y1 - 2014

N2 - The propagation of compressional Pi 2 waves in the inner magnetosphere is investigated by analyzing the onset delay times between the ground and the geosynchronous altitude. We use the compressional component (northward) of magnetic data from low-latitude stations and the geosynchronous satellite ETS-VIII (GMLat. =−10.8°, GMLon. = 217.5°). The onset delays are determined by a cross-correlation analysis, and we analyzed the events with high waveform correlations (correlation coefficient greater than 0.75). Some of these high-correlation events have the properties of propagating waves; Pi 2 waveforms at the ground stations and the satellite were synchronized with each other when the data were shifted by onset delays. The results of the statistical analysis show that 87% of the Pi 2 onsets at a ground station (Kuju, GMLat. = 26.13°, GMLon. = 202.96°) were delayed from the Pi 2 onsets at ETS-VIII, and the average of the delay times was 29 sec. This clearly shows Pi 2 onsets (initial perturbations of Pi 2) propagated from the geosynchronous altitude to the low-latitude ground. The delay times tended to be larger around the midnight sector than around the dawn and dusk sectors. These results are consistent with two-dimensional propagation of fast waves estimated by the model of Uozumi et al. (J Geophys Res 114:A11207, 2009). The delay times are nearly identical to the travel time of fast waves from geosynchronous altitude to the low-latitude ground, and the local time variation of the delay shows the azimuthal propagation along the geosynchronous orbit. We conclude that the initial compressional perturbations of Pi 2 waves propagate radially and longitudinally as a fast wave in the inner magnetosphere.

AB - The propagation of compressional Pi 2 waves in the inner magnetosphere is investigated by analyzing the onset delay times between the ground and the geosynchronous altitude. We use the compressional component (northward) of magnetic data from low-latitude stations and the geosynchronous satellite ETS-VIII (GMLat. =−10.8°, GMLon. = 217.5°). The onset delays are determined by a cross-correlation analysis, and we analyzed the events with high waveform correlations (correlation coefficient greater than 0.75). Some of these high-correlation events have the properties of propagating waves; Pi 2 waveforms at the ground stations and the satellite were synchronized with each other when the data were shifted by onset delays. The results of the statistical analysis show that 87% of the Pi 2 onsets at a ground station (Kuju, GMLat. = 26.13°, GMLon. = 202.96°) were delayed from the Pi 2 onsets at ETS-VIII, and the average of the delay times was 29 sec. This clearly shows Pi 2 onsets (initial perturbations of Pi 2) propagated from the geosynchronous altitude to the low-latitude ground. The delay times tended to be larger around the midnight sector than around the dawn and dusk sectors. These results are consistent with two-dimensional propagation of fast waves estimated by the model of Uozumi et al. (J Geophys Res 114:A11207, 2009). The delay times are nearly identical to the travel time of fast waves from geosynchronous altitude to the low-latitude ground, and the local time variation of the delay shows the azimuthal propagation along the geosynchronous orbit. We conclude that the initial compressional perturbations of Pi 2 waves propagate radially and longitudinally as a fast wave in the inner magnetosphere.

KW - Fast-mode wave

KW - Geosynchronous orbit

KW - Pi 2 pulsation

KW - ULF wave

KW - Wave propagation

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U2 - 10.1186/1880-5981-66-20

DO - 10.1186/1880-5981-66-20

M3 - Article

AN - SCOPUS:85021671473

VL - 66

JO - Earth, Planets and Space

JF - Earth, Planets and Space

SN - 1343-8832

IS - 1

M1 - 20

ER -