Observations of polarization electric fields and plasma drifts associated with low-latitude TIDs

Abstract:

Ionospheric plasma structures and TIDs are often observed in the conjugate hemispheres. It is widely believed that the polarization electric field is responsible for the conjugacy. However, observed conjugate disturbances so far are mostly in plasma density and TEC, and there is almost no report of observations of polarization electric fields associated with TIDs. We present the C/NOFS measurements of TID-like disturbances in the plasma density and drift velocity. The plasma drift perpendicular to the geomagnetic field is manifestation of the polarization electric field. Plasma flow parallel to the geomagnetic field is highly correlated with the polarization electric field and is consistent with the prediction of TID theories, confirming that the polarization electric field is caused by TIDs. Surprisingly, the polarization electric field is observed not only at night but also during daytime, implying that the polarization electric field is not shorted out by the dayside E layers. The satellite data are compared with the Jicamarca radar data when C/NOFS is 20 degrees away from the radar but nearly at the same magnetic latitude (along the same field lines). This may be the first observation of polarization electric field associated with TIDs and verifies that the polarization electric field can be indeed transmitted thousands of kilometers along the geomagnetic field lines. The observations provide direct evidence for justifying the mechanism for the generation of similar ionospheric disturbances in the conjugate hemispheres.