Polar cap patch segmentation of the tongue of ionization in the morning convection cell

Q.‐H. Zhang,B.‐C. Zhang,M. Lockwood,R.‐Y. Liu,J. Moen,S.‐R. Zhang,H.‐Q. Hu,M. Lester,I. W. McCrea,H.‐G. Yang

doi:10.1002/grl.50616

Abstract

AbstractTwo types of poleward moving plasma concentration enhancements (PMPCEs) were observed during a sequence of pulsed reconnection events, both in the morning convection cell: Type L (low density) was associated with a cusp flow channel and seems likely to have been produced by ionization associated with particle precipitation, while Type H (high density) appeared to originate from the segmentation of the tongue of ionization by the processes which produced the Type L events. As a result, the Type L and Type H PMPCEs were interspersed, producing a complex density structure which underlines the importance of cusp flow channels as a mechanism for segmenting and structuring electron density in the cusp and shows the necessity of differentiating between at least two classes of electron density patches.

Highlights

[1] Two types of poleward moving plasma concentration enhancements (PMPCEs) were observed during a sequence of pulsed reconnection events, both in the morning convection cell: Type L was associated with a cusp flow channel and seems likely to have been produced by ionization associated with particle precipitation, while Type H appeared to originate from the segmentation of the tongue of ionization by the processes which produced the Type L events
We will illustrate the roles of both Type L PMPCEs and Type H PMPCEs in creating the complex density structures seen in the cusp region
There are four different plasma regimes: (1) background of cold and low density plasma at lower latitudes observed in the GPS total electron content (TEC) and European Incoherent Scatter (EISCAT) VHF; (2) enhanced electron densities, consisting of cold dense plasma in the GPS TEC data constituting the source of the tongue of ionization (TOI); (3) PMPCEs in the VHF radar data, possibly created by cusp reconnection/precipitation events, which evolved poleward to form the minima between the polar cap patches measured by the ESR; and (4) the background plasma in the polar cap seen after 0825 UT by the ESR, characterized by very low temperatures and densities

Summary

Introduction

[1] Two types of poleward moving plasma concentration enhancements (PMPCEs) were observed during a sequence of pulsed reconnection events, both in the morning convection cell: Type L (low density) was associated with a cusp flow channel and seems likely to have been produced by ionization associated with particle precipitation, while Type H (high density) appeared to originate from the segmentation of the tongue of ionization by the processes which produced the Type L events. After about 0750 UT, the electron density appeared smooth and relatively high between about 70 and 73 magnetic latitude (at an altitude between about 200 and 300 km), suggesting that the formation of PMPCEs in the EISCAT VHF viewing area ceased as the IMF began to turn northward.

Results

Conclusion