Modulation of equatorial electrojet irregularities by atmospheric gravity waves

Abstract

On 9 January 2002 and 14 November 2001, the São Luís 30 MHz coherent backscatter radar observed unusual daytime echoes scattered from the equatorial electrojet. The electrojet echoing layers on these days, as seen in the range time intensity maps, exhibited quasiperiodic oscillations. Time-frequency decomposition of the magnetic field perturbations ΔH, measured simultaneously by the ground-based magnetometers, also showed evidence of short-period waves. The ground-based observations were aided by measurements of the brightness temperature in the water vapor and infrared bands made by the GOES 8 satellite. The GOES 8 satellite measurements indicated evidence of deep tropospheric convection activities, which are favorable for the launch of atmospheric gravity waves (AGW) near São Luís. Our multitechnique investigation, combined with an analysis of the equatorial electric field and current density, indicates that AGW forcing could have been responsible, via coupling with E region electric fields, for the short-period electrojet oscillations observed over São Luís.

Effects of Electric Field and Neutral Wind on the Asymmetry of Equatorial Ionization Anomaly

“…A close comparison between the meridional neutral wind estimated from the ensemble of LLIONS runs and SOFDI measurements shows a reasonable agreement with respect to magnitude and direction. During quiet days, electric field fluctuations in the EEJ altitudes are rare because the background electric field mostly overwhelms wind‐driven perturbation electric fields (Kelley, ; Shume et al, ). The modeled patterns of meridional neutral wind also show a trend similar to the variations of the SOFDI measurements.…”

TID Observations and Source Analysis During the 2017 Memorial Day Weekend Geomagnetic Storm Over North America

“…For example, the studies by Vadas and Liu (), Azeem et al (), and Jonah et al () used tropospheric convective plumes perturbation sources to show a global and regional GW associated perturbation in TEC. Nakamura et al () and Shume et al () also used tropospheric convective plumes perturbations source to show connections between usual periodicity in the intensity of EEJ current and the preferred propagation direction of GW in an all‐sky imager during all seasons of the year. These and other related studies clearly demonstrate the importance of troposphere‐ionosphere coupling through convection activity as an important factor of AGW/TID seeding in the ionosphere.…”

Anomalous Responses of the F2 Layer Over the Brazilian Equatorial Sector During a Counter Electrojet Event: A Case Study

“…As mentioned by Shume et al. (2014), gravity waves with a vertical wavelength of less than 50 km can interact with the background dynamo field in the electrojet and cause electric field variations with altitude.…”