Variabilities of the equatorial electrojet in Brazil and Peru

摘要

This report presents seasonal and longitudinal variabilities of the equatorial electrojet in the east (Brazil, Sao Luis: 2.3° S; 315.8° E; 0.5° S dip latitude) and west (Jicamarca, 11.95° S; 283.13° E; 0.6° N dip latitude) coasts of the continent of South America. Groundbased magnetic field perturbation measurements |¤H for solar maximum (2001/2002) and solar minimum (2006/2007) conditions from the two equatorial stations (Sao Luis and Jicamarca) have been used for the study. The |¤H signal which is a measure of the strength of the equatorial electrojet is spectrally analyzed using wavelet analysis. The results of our analysis show that (1) the equatorial electrojet has maxima around equinoxes in Jicamarca, Peru but it has a prominent maximum during Southern Hemisphere summer (centered about December/January) in Sao Luis, Brazil. The observed seasonal behavior of the equatorial electrojet in Sao Luis is highly likely due to the large magnetic declination angle (about 20° west) there. (2) The equatorial electrojet is stronger in the west coast (Jicamarca) compared to the east coast (Sao Luis), irrespective of solar activity condition. (3) The magnitude of the equatorial electrojet is more variable with season and solar cycle over Sao Luis than over Jicamarca.