Theoretical effects of geomagnetic activity on thermospheric tides

Journal Article · Wed Sep 01 04:00:00 EDT 1993 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/93JA01188· OSTI ID:86370

Fesen, C G ^[1]; Richmond, A D; Roble, R G ^[2]

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1. Dartmouth College, Hanover, NH (United States)
2. National Center for Atmospheric Research, Boulder, CO (United States)

The theoretical effects of auroral activity on thermospheric tides during equinox solar cycle minimum are investigated using simulations from the National Center for Atmospheric Research thermosphere-ionosphere general circulation model. One set of model runs examined the effects of increasing levels of geomagnetic activity on the neutral horizontal winds and temperatures. A second set of model runs examined the generation of diurnal and semidiurnal waves in the neutral horizontal winds and temperatures by solar forcing, auroral forcing, and waves propagating vertically from the lower atmosphere. The model simulations were made for four levels of geomagnetic activity, parameterized principally by the total hemispheric power index and the potential drop across the polar cap. The resulting neutral horizontal wind and temperature fields were examined at geographic latitudes of 17.5{degrees}N, 42.5{degrees}N, and 67.5{degrees}N at 70{degrees}W longitude. The modeled response to the level of geomagnetic activity varies with altitude and latitude: the effects tend to maximize at high altitudes and high latitudes and penetrate lower in altitude as geomagnetic activity increases. The simulated mean temperatures increase and the mean winds become more southward and westward at all latitudes with increasing auroral activity. In the upper thermosphere, the model diurnal temperature amplitudes decrease with increasing activity, while the diurnal meridional wind amplitudes increase. The modeled semidiurnal winds are strongly affected by the level of geomagnetic activity, while the semidiurnal temperatures are not. Analysis of the second set of model simulations focusing on the generation of the tidal waves indicates that the tidal response to auroral activity is largely determined by the interference between the waves due to upward propagating tides and in situ solar forcing and those generated by the auroral momentum and energy sources. 28 refs., 19 figs.

• Sponsoring Organization: USDOE
• OSTI ID: 86370
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A9 Vol. 98; ISSN 0148-0227; ISSN JGREA2
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ACTIVITY LEVELS
AMBIENT TEMPERATURE
DAILY VARIATIONS
GEOMAGNETIC FIELD
THERMOSPHERE
TIDE
WIND