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The response of high‐latitude convection to a sudden southward IMF turning
Author(s) -
Ruohoniemi J. M.,
Greenwald R. A.
Publication year - 1998
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/98gl02212
Subject(s) - noon , convection , geology , midnight , ionosphere , latitude , high latitude , interplanetary magnetic field , geophysics , atmospheric sciences , geodesy , physics , meteorology , solar wind , plasma , astronomy , quantum mechanics
We describe the response of the high‐latitude convection to a sudden southward turning of the IMF. In this event B Z recorded at the WIND satellite switched from +6 nT to −6 nT in 2½ minutes and effects in the ionosphere were observed by the SuperDARN HF radars. In the vicinity of noon MLT, the convection switched suddenly (∼2 min) from sunward to antisunward with the velocity change reaching magnitudes as great as 1500 m/s in about 6 minutes. Surprisingly, the responses at the other MLTs distributed from noon to midnight began at virtually the same time. Meridional flows near 22 MLT were observed to reverse direction in about 4 minutes with the velocity change reaching magnitudes as great as 750 m/s in about 8 minutes. This example shows that the convection can respond to a sudden IMF change practically simultaneously (∼2 min) over the entire high‐latitude zone and reconfigure from a pattern characteristic of B Z + to one characteristic of B Z − in a very short (2–4 min) time.