Different responses of northern and southern high latitude ionospheric convection to IMF rotations: a case study based on SuperDARN observations
We use SuperDARN data to study high-latitude ionospheric convection over a three hour period (starting at 22:00 UT on 2 January 2003), during which the Interplanetary Magnetic Field (IMF) flipped between two states, one with <I>B<sub>y</sub></I>>>|<I>B&...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2009-06-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/27/2423/2009/angeo-27-2423-2009.pdf |
| Summary: | We use SuperDARN data to study high-latitude ionospheric convection over a
three hour period (starting at 22:00 UT on 2 January 2003), during which the
Interplanetary Magnetic Field (IMF) flipped between two states, one with
<I>B<sub>y</sub></I>>>|<I>B<sub>z</sub></I>| and one with <I>B<sub>z</sub></I>>0, both with negative <I>B<sub>x</sub></I>. We
find, as expected from previous works, that day side ionospheric convection
is controlled by the IMF in both hemispheres. For strongly northward IMF, we
observed signatures of two reverse cells, both in the Northern Hemisphere
(NH) and in the Southern Hemisphere (SH), due to lobe reconnection. On one
occasion, we also observed in the NH two viscous cells at the sides of the
reverse cell pair. For duskward IMF, we observed in the NH a large dusk
clockwise cell, accompanied by a smaller dawn cell, and the signature of a
corresponding pattern in the SH. On two occasions, a three cell pattern,
composed of a large clockwise cell and two viscous cells, was observed in the
NH. As regards the timings of the NH and SH convection reconfigurations, we
find that the convection reconfiguration from a positive <I>B<sub>z</sub></I> dominated to a
positive <I>B<sub>y</sub></I> dominated pattern occurred almost simultaneously (i.e. within
a few minutes) in the two hemispheres. On the contrary, the reconfiguration
from a <I>B<sub>y</sub></I> dominated to a northward IMF pattern started in the NH 8–13 min
earlier than in the SH. We suggest that part of such a delay can be due
to the following mechanism: as IMF <I>B<sub>x</sub></I><0, the northward-tailward
magnetosheath magnetic field reconnects with the magnetospheric field first
tailward of the northern cusp and later on tailward of the southern cusp, due
to the IMF draping around the magnetopause. |
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| ISSN: | 0992-7689 1432-0576 |