Abstract. Daytime equatorial electrojet plasma irregularities were investigated using five distinct radar diagnostics at Jicamarca including range-time-intensity (RTI) mapping, Faraday rotation, radar imaging, oblique scattering, and multiplefrequency scattering using the new AMISR prototype UHF radar. Data suggest the existence of plasma density striations separated by 3-5 km and propagating slowly downward. The striations may be caused by neutral atmospheric turbulence, and a possible scenario for their formation is discussed. The Doppler shifts of type 1 echoes observed at VHF and UHF frequencies are compared and interpreted in light of a model of Farley Buneman waves based on kinetic ions and fluid electrons with thermal effects included. Finally, the up-down and east-west asymmetries evident in the radar observations are described and quantified.
[1] Zonal wind profiles in the daytime equatorial electrojet are inferred from the Doppler shifts of type II radar echoes observed at the Jicamarca Radio Observatory (JRO) in Perú. The inference is based on a three-dimensional electrostatic potential model. The model includes anomalous effects and is constrained by radar and magnetometer data. The amplitude and phase of the calculated zonal wind profiles are in general agreement with representative wind profiles measured by the WINDII instrument on board the Upper Atmosphere Research Satellite (UARS). The calculated winds also have the same general characteristics as zonal wind profiles measured by rocket-borne chemical release experiments. However, the magnitude of the latter are larger than the former. The temporal behavior of the calculated zonal winds suggests a downward phase progression with a roughly semidiurnal period.
Global Navigation Satellite System (GNSS) is used in seismology to study the ground displacements as well as to monitor the ionospheric total electron content (TEC) perturbations following seismic events. The aim of this work is to combine these two observations in one real-time method based on the Total Variometric Approach (TVA) to include the GNSS real-time data stream in future warning systems and tsunami genesis estimation observing both, ground motion and TEC. Our TVA couples together the Variometric Approach for Displacement Analysis Stand-alone Engine (VADASE) with the Variometric Approach for Real-Time Ionosphere Observation (VARION) algorithms. We apply the TVA to the Mw 8.3 Illapel earthquake, that occurred in Chile on September 16, 2015, and we demonstrate the coherence of the earthquake ground shaking and the TEC perturbation by using the same GNSS data stream in a real-time scenario. Nominally, we also highlight a stronger kinetic energy released in the north of the epicenter and visible in both, the ground motion and the TEC perturbation detect at 30 s and around 9.5 min after the rupture respectively. The high spatial resolution of ionospheric TEC measurement seems to match with the extent of the seismic source. The GNSS data stream by TVA of both the ground and ionospheric measurement opens today new perspectives to real-time warning systems for tsunami genesis estimation.
[1] This report presents seasonal and longitudinal variabilities of the equatorial electrojet in the east (Brazil, São Luís: 2.3°S; 315.8°E; 0.5°S dip latitude) and west (Jicamarca, Perú: 11.95°S; 283.13°E; 0.6°N dip latitude) coasts of the continent of South America. Ground-based magnetic field perturbation measurements DH for solar maximum (2001/2002) and solar minimum (2006/2007) conditions from the two equatorial stations (São Luís and Jicamarca) have been used for the study. The DH 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, Perú but it has a prominent maximum during Southern Hemisphere summer (centered about December/January) in São Luís, Brazil. The observed seasonal behavior of the equatorial electrojet in São Luís 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 (São Luís), irrespective of solar activity condition. (3) The magnitude of the equatorial electrojet is more variable with season and solar cycle over São Luís than over Jicamarca.
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