That is, upwelling amplification could result from the interchange instability driven by the eastward electric field (E) that is responsible for the PSSR (gravity is likely a lesser player because the altitude of the bottomside F layer is, at this time, still relatively low).
In contrast, the model of a data interchange is driven by the needs of conveying data among applications.
In this paper, we show that upwelling growth controls EPB development, and that upwelling growth, itself, may be driven by PSSR and the interchange instability during high solar activity, but not by PSSR during low solar activity (see "Upwelling growth: weak PSSR" section).
Backscatter along the west wall could be produced by the interchange instability driven by an eastward U. Absence of EPBs in the presence of the other two features, however, calls for some discussion.
The first two, taken together, appear consistent with the notion that they are produced by the interchange instability, driven by orthogonal forces.
Hence, the ion-neutral collision frequency (v in ) is smallest during onset phase, and the linear growth rate of the interchange instability (driven by gravity) (Dungey 1956) reaches a maximum.
Interpretation of west-wall structuring via the interchange instability, driven by an eastward U, appears straightforward.
On the other hand, the west wall of an upwelling would be unstable to the interchange process, driven by an eastward U (Tsunoda 1983).
Given the ubiquity of small-amplitude LSWS and only the occasional development of EPBs, Eccles (2004) concluded that upwellings determine the locations where EPBs appear, but it must be the interchange instability, driven by PSSR, that controls EPB development.
