HR: 0800h
AN: SA31A-09    [Abstracts]
TI: Spectral Study of the Equatorial Electric and Magnetic Fields
AU: * Kelley, M C
EM: mikek@ece.cornell.edu
AF: Cornell University, School of Electrical and Computer Engineering, 320 Rhodes Hall, Ithaca, NY 14853, United States
AU: Rothman, R
EM: rer29@cornell.edu
AF: Cornell University, School of Electrical and Computer Engineering, 320 Rhodes Hall, Ithaca, NY 14853, United States
AU: Nicolls, M J
EM: michael.nicolls@sri.com
AF: SRI International, Center for Geospace Studies, 333 Ravenswood Avenue, Menlo Park, CA 94025, United States
AB: We report on the spectral analysis of four years of daytime electric and magnetic field data obtained near the magnetic equator. The former were obtained using the JULIA radar system at the Jicamarca Radio Observatory using the so-called 150 km echo, which can be used reliably to determine the zonal electric field component during daytime. The magnetic field data were obtained using magnetometers located at Jicamarca and Piura in Peru. Due to the nighttime data gap, we can study variations with periods longer than two days and shorter than eight hours. Our goal for the longer periods is to study the variability of atmospheric drivers of the equatorial electrojet. This is straightforward for the electric field, but requires subtracting the ring current and other external effects from the magnetic field data. This is done by using the Gonzales/Anderson technique and employing the two magnetic field measurements. The electrojet strength decreased almost linearly over the four-year period as the solar cycle wound down. Spectral analysis reveals a clear semi-annual peak with maxima at the equinoxes and a secondary peak with a period of fourteen days. The latter seems to indicate that the lunar gravitational tide adds constructively to the semi-diurnal solar thermal tide. At higher frequencies the data must be parsed according to magnetic activity and solar wind conditions due to the importance of penetrating electric fields from the solar wind, and will be presented in this format.
DE: 2415 Equatorial ionosphere
DE: 3384 Acoustic-gravity waves
SC: SPA-Aeronomy [SA]
MN: 2007 Joint Assembly