Electric field control of E region coherent echoes: Evidence from radar observations at the South Pole

E-ISSN： 2169-9402|120|3|2148-2165

ISSN： 2169-9380

Source： JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS, Vol.120, Iss.3, 2015-03, pp. : 2148-2165

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

Previous Menu Next

Abstract

AbstractCharacteristics and formation mechanisms of E region plasma irregularities at high latitudes are investigated using observations with the newly deployed Super Dual Auroral Radar Network (SuperDARN) radar at the South Pole Antarctic station (SPS) near a magnetic latitude (MLAT) of 75°S. It is shown that E region echo occurrence at SPS exhibits a diurnal variation that is significantly different from those at auroral and polar cap latitudes. Moreover, analysis of major spectral populations also showed a distinct and previously unreported diurnal pattern. The plasma drift velocity estimates are derived at E region ranges of SPS, leveraging the SPS radar's position well within the MLAT region where SuperDARN convection estimates are well constrained by the data. It is shown that E region irregularity occurrence increases when the convection direction is within the SPS field of view and/or when the plasma drift component is comparable with the nominal ion‐acoustic speed Cs of 350 m/s. This is the expected behavior for irregularities generated directly by the modified two‐stream plasma instability (MTSI). On the other hand, irregularity velocity dependence on convection velocity showed an unexpected saturation at velocity values smaller than nominal Cs. It is demonstrated that the convection velocity at which irregularity velocity starts to differ from the convection component and to approach a maximum value is dependent on the magnetic aspect angle. Moreover, the maximum velocity value itself also depends on the aspect angle. The observed behavior is discussed in context of recent models that involve evolving aspect angles as a key characteristic of MTSI saturation.