Coordinated incoherent scatter radar observations of the Semidiurnal tide in the lower thermosphere

Journal Article · Fri Feb 01 04:00:00 EST 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/90JA01529· OSTI ID:5316282

Salah, J E ^[1]; Johnson, R M ^[2]; Tepley, C A ^[3]

---

1. Massachusetts Inst. of Tech., Westford (USA)
2. Univ. of Michigan, Ann Arbor (USA)
3. National Astronomy and Ionosphere Center, Arecibo (Puerto Rico)

The incoherent scatter radars at Arecibo (18.3{degree}N), Millstone Hill (42.6{degree}N), and Sondrestrom (67{degree}N) simultaneously observed the thermal structure and dynamics of the Earth's lower thermosphere during the period September 21-25, 1987, as part of the Lower Thermosphere Coupling Study. Plasma spectral measurements were used to derive ion temperatures and horizontal neutral wind velocities in the altitude region 90-140 km, and semidiurnal harmonics were determined from the data sets. The daily mean temperatures were found to be within 40{degree}K at the three stations, and the largest semidiurnal temperature amplitudes, exceeding 70{degree}K above 115 km, were recorded at Arecibo. Mean winds were about {plus minus}30 m/s at most altitudes, shifting from eastward to westward directions at 115 km, and the semidiurnal amplitudes were in the range 20-70 m/s. Phase variations with height reveal reasonable consistency among the three stations, within 3-4 hours, and indicate an average vertical wavelength of 40-70 km. However, a strong variation is seen in the vertical structure in the 110- to 130-km region, suggesting the presence of different tidal modes. Comparison with the most current tidal propagation model by Forbes and Vial (this issue) indicates that the model tends to underestimate the amplitudes for this time period, particularly above 110 km. By virtue of the latitudinal distribution of the three radars their coordinated observations of the lower thermosphere serve to constrain numerical models and improve their understanding of this important yet complex region of the atmosphere.

• OSTI ID: 5316282
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 96:A2; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640200* -- Atmospheric Physics
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALTITUDE
AMPLITUDES
COMPARATIVE EVALUATIONS
DIMENSIONS
DYNAMICS
EARTH ATMOSPHERE
EVALUATION
HARMONICS
HEIGHT
ION TEMPERATURE
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
MECHANICS
MORPHOLOGY
OSCILLATIONS
RADAR
RANGE FINDERS
TEMPERATURE MEASUREMENT
THERMOSPHERE
TIDE
VARIATIONS
WIND