Horizontal Parameters of Daytime Thermospheric Gravity Waves and E Region Neutral Winds over Puerto Rico

Abstract

We report on the electron density perturbation amplitudes, periods (up to 60 min), horizontal and vertical wavelengths, phase speeds, and propagation directions of daytime traveling ionospheric disturbances (TIDs) from 115 to 300 km altitude using dual-beam experiments at the Arecibo Observatory (AO), Puerto Rico. As in previous studies, we find a near continuum of waves above the AO. While the TIDs propagate in nearly all directions except purely westward, we find that most propagate southward southeastward. We find that TID amplitudes increase nearly exponentially with increasing period, although with a much smaller slope for periods >30 min. TID amplitudes peak on the bottomside of the F region. Typical vertical wavelengths increase from less than 50 km at low altitudes to ∼100–300 km. Horizontal wavelengths increase from ∼70–100 km to ∼150–500 km over the same altitude range. Median vertical wavelengths, horizontal wavelengths, and periods increase with altitude up to z∼<225 km and are approximately constant at higher altitudes. Horizontal phase speeds are >100–150 m/s. We also measure the E region horizontal neutral winds and find that they peak at ∼150 m/s near z∼105 km in the middle of the day. Wave phase speeds are in general greater than these ambient winds. In addition, by tracing individual wave packets vertically in altitude, we find that a packet’s vertical wavelength generally peaks near the altitude where its inferred ion velocity amplitude is maximum. The vertical wavelength generally decreases above this altitude, an observation that is consistent with gravity wave packet theory.