Day-time F region echoes observed by the Sao Luis radar

作者：Shume E B^*; Rodrigues F S; de Paula E R; Batista I S; Butala M D; Galvan D A

来源：Journal of Atmospheric and Solar-Terrestrial Physics, 2013, 103: 48-55.

DOI：10.1016/j.jastp.2013.02.003

• Plasma irregularities
• Electric fields
• Conductivities
• F region equatorial ionosphere
• Radar observation

This brief report presents unique day-time F region coherent scatter echoes observed by the 30 MHz radar over Sao Luis in eastern Brazil. The radar observation was part of the July 2011 radar campaign designed to detect echoes from day-time F region irregularities. These rare day-time F region radar echoes, scattered from short wavelength plasma irregularities, have quasi patchy features. They are characterized by large upward Doppler velocities (similar to 100-200 m/s). They are very weak (by more than 10 dB) when compared to radar echoes observed over Sao Luis scattered from the night-time F plasma irregularities known as equatorial spread F. Simultaneous GPS vertical total electron content (TEC), and F-2 peak frequency (f(o)F(2)) and F-2 peak height (h(m)F(2)) estimated from ionosonde measurements over Sao Luis have provided additional evidence that the received day-time F region radar echoes were from genuine ionospheric scatterers. This report suggests physical explanations for the day-time radar echoes in terms of the generalized Rayleigh-Taylor instability mechanism operating on large magnetic declination (similar to 20 degrees westward) of the geomagnetic field geometry in Sao Luis, conductivity distribution in the winter southern hemisphere and summer northern hemisphere, and the resulting magnetic flux tube electric field configurations.

• 出版日期2013-10