Counter electrojet features in the Brazilian sector: simultaneous observation by radar, digital sounder and magnetometers

Abstract

Abstract.In the present work we show new results regarding equatorial counter electrojet (CEJ) events in the Brazilian sector, based on the RESCO radar, two set of fluxgate magnetometer systems and a digital sounder. RESCO radar is a 50 MHz backscatter coherent radar installed in 1998 at São Luís (SLZ, 2.33 • S, 44.60 • W), an equatorial site. The Digital sounder routinely monitors the electron density profile at the radar site. The magnetometer systems are fluxgate-type installed at SLZ and Eusébio (EUS, 03.89 • S, 38.44 • W). From the difference between the horizontal component of magnetic field at SLZ station and the same component at EUS (EEJ ground strength) several cases of westward morning electrojet and its normal inversion to the eastward equatorial electrojet (EEJ) have been observed. Also, the EEJ ground strength has shown some cases of CEJ events, which been detected with the RESCO radar too. Detection of these events were investigated with respect to their time and height of occurrence, correlation with sporadic E (Es) layers at the same time, and their spectral characteristics as well as the radar echo power intensity.

Relationships between pre-sunset electrojet strength, pre-reversal enhancement and equatorial spread-F onset

“…We used 5 min values calculated from 1 min ones for analyses, since EEJ variations with a time scale more than 10 min are required in this study. The EEJ ground strength was estimated by subtracting the H-component at KTB outside the EEJ region from that at PKT inside the EEJ region according to many previous studies (e.g., Mayaud, 1977;Denardini et al, 2009). The subtraction was performed to minimize the difference between the H-components at PKT and KTB over the period from 21:00 to 05:00 LT at PKT (LT at PKT is 6.6 h ahead of UT).…”

“…In this study, the EEJ current was evaluated by using its magnetic effect at the ground level referred as the EEJ ground strength (Denardini et al, 2009). The EEJ ground strength was calculated from H-components that were obtained from magnetometers installed at Phuket (PKT: 8.1 • N, 98.3 • E; 0.1 • N magnetic latitude) and at Kototabang (KTB: 0.2 • S, 100.3 • N; 10.0 • S magnetic latitude).…”

The Initial Steps for Developing the South American K Index From the Embrace Magnetometer Network

“…Although the subscript 'p' intended to mean planetary (from the German word planetarische ), the South American sector is poorly represented in Kp deviation. Also, from previous works using magnetic data obtained in South America (Trivedi et al, 2005;Denardini et al, 2009Denardini et al, , 2011Moro et al, 2012), we have verified some peculiarities with respect to the magnetic variations due to the electric fields associated with the Sq current system (during quit and disturbed periods) and magnetospheric current system (the ring current during disturbed periods) that we were not able to explain using the classical magnetic indices like AE, Dst and Kp (Rostoker, 1972). Therefore, we decided to create the Embrace Magnetometer Network to provide reliable magnetic data from several part of the South American territory and to start developing the South American K index (Ksa), which can be confronted with the traditional Kp to check its validity.…”

A discussion about some aspects of the solar-terrestrial systems coupling with regard to space weather effects

“…Finally, the diurnal variation of the EEJ ground strength is estimated by taking the difference between the ΔH values at a station at the dip equator (ΔH SLZ ) and that at a station nearby the dip equator but outside the EEJ influence (ΔH VSS ). A more detailed explanation on the magnetic data treatment and on the use two stations is explained by Denardini et al (2009).…”