Interhemispheric observations of nightside ionospheric electric fields in response to IMF Bz and By changes and substorm pseudobreakup
Other literature type
Yeoman, T. K.
Lewis, R. V.
Cowley, S. W. H.
Ruohoniemi, J. M.
(issn: 1432-0576, eissn: 1432-0576)
HF radar data during equinoctial, small IMF <i>B<sub>y</sub></i>
conditions have enabled the ionospheric convection during the substorm growth
phase and substorm pseudobreakup to be studied in both hemispheres. This has
revealed both conjugate and non-conjugate convection behaviour during the
substorm growth phase before and after the pseudobreakup onset. The nightside
convection pattern is found to respond promptly to the southward turning of the
interplanetary magnetic field (IMF) which impacts on the dusk flank of the
magnetosphere due to an inclined phase front in the IMF in the case study
presented. The subsequent interhemispheric observations of nightside convection
are controlled by the IMF <i>B<sub>y</sub></i> polarity. The time scale for the
response to changes in the IMF <i>B<sub>y</sub></i> component is found to be a
little longer than for <i>B<sub>z</sub></i>, and the full impact of the IMF <i>B<sub>y</sub></i>
is not apparent in the nightside convection until after substorm pseudobreakup
has occurred. The pseudobreakup itself is found to result in a transitory
suppression in the ionospheric electric field in both hemispheres. This flow
suppression is very similar to that observed in HF radar observations of full
substorm onset, with the exception of a lack of subsequent poleward expansion.<br><br><b>Key words: </b>Ionosphere (auroral ionosphere) -
Magnetospheric physics (magnetosphere-ionosphere interactions; storms and