Seasonal variations in the thermosphere above Millstone Hill

Journal Article · Fri Feb 01 04:00:00 EDT 1974 · Radio Science

DOI:https://doi.org/10.1029/RS009i002p00231· OSTI ID:4342769

Salah, J. E.; Evans, J. V.; Wand, R. H.

incoherent scatter radar measurements gathered since 1969 at Millstone Hill (42.6 deg N, 71.5 deg W) are used to study the seasonal variations of the neutral gas temperature, composition and wind velocity in the thermosphere. Between 110 and 120 km, the mean temperature is found to oscillate with a 20 K annual amplitude, 10 K semiannual amplitude, and maxima in July; the mean density oscillates with an annual amplitude of 13% of the mean and a semiannual amplitude of 6% of the mean with maxima in November. Similarly, the mean daily exospheric temperature possesses a 100 K amplitude variation with a maximum in summer; the semiannual component is only about 10 K. Moreover, a weak winter maximum characterizes the neutral density at 400 km, and the neutral wind at 300 km is found to blow northward for a longer period during the day in winter than in summer. The amplitude and phase of the daily semidiurnal tides in the lower thermosphere do not vary systematically with season but a large variability is observed from day to day, particularly in the phase of the oscillation during winter. In contrast, the semidiurnal harmonic of the exospheric temperature varies seasonally in amplitude and phase and reflects the controlling influence of the length of the day on the shape of ihe daily temperature oscillation. In the middle thermosphere, the neutral composition ratio O/N/sub 2/ is larger in winter than summer, with a rapid transition at the equinox.

• Research Organization: Massachusetts Inst. of Tech., Lexington
• Sponsoring Organization: USDOE
• NSA Number: NSA-29-027589
• OSTI ID: 4342769
• Journal Information: Radio Science, Journal Name: Radio Science Journal Issue: 2 Vol. 9; ISSN 0048-6604
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

*THERMOSPHERE-- SEASONAL VARIATIONS
CHEMICAL COMPOSITION
INCOHERENT SCATTERING
N58100* --Physics (Atmospheric)--Auroral & Ionospheric Phenomena