The June 1991 thermospheric storm observed in the southern hemisphere

Journal Article · Thu Sep 01 04:00:00 EDT 1994 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/94JA01101· OSTI ID:166282

Smith, R W ^[1]; Hernandez, G; Clark, K C ^[2]

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1. Univ. of Alaska, Fairbanks, AK (United States)
2. Univ. of Washington, Seattle, WA (United States); and others

Neutral upper thermospheric wind and temperature measurements obtained at South Pole, Antarctica (90{degrees}S, 75{degrees} invariant latitude (INV)), and Mt John, New Zealand (44{degrees}S, 171{degrees}E, 52{degrees} INV) during the storm period June 11-13 1991 are presented. Winds peaking at about 800 m/s and typical temperatures reaching up to 2000 K were found in the polar cap. Peak winds above Mount John reached 300 m/s in response to the strong high-latitude forcing which had spread equatorward to midlatitudes. The temperature predictions of the MSIS 86 model were in broad agreement with the observations but were overestimates by several hundred degrees near 0800 UT on June 12 and underestimates by a similar amount near 0800 UT on June 13. The observed meridional winds at South Pole were less uniform and few hours different in phase than indicated by the vector spherical harmonic (VSH) model predictions. Although the wind magnitudes were similar to VSH at most times, there was a 12 hour difference in the phase in the zonal component. For the Mount John observations the VSH model predictions exaggerated the equatorward penetration of the polar thermospheric circulation relative to the observations. Predicted zonal winds exceeded observations at almost all times. The observed wind pattern at Mount John differed from normal midlatitude quiescent behavior according to the usual pattern but not in simple proportionality with the variations of geomagnetic activity, expressed as Ap or Kp. It is suggested that the sign of the interplanetary magnetic field Y component is an important factor which determines how momentum is coupled between high and middle latitudes during storms and that it will be needed in the specifications for models such as VSH. 36 refs., 5 figs.

• OSTI ID: 166282
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A9 Vol. 99; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
AMBIENT TEMPERATURE
COUPLING
MAGNETIC STORMS
SOUTHERN HEMISPHERE
THERMOSPHERE
WIND