Low‐latitude mesospheric turbulence investigated using coordinated MST radar and rocket‐borne observations from India

In this paper we present and discuss observational results on low‐latitude mesospheric turbulence obtained from a coordinated experiment made using a Langmuir probe (LP) onboard a rocket launched from Sriharikota (13.6°N, 80.2°E) and the mesosphere‐stratosphere‐troposphere (MST) radar from Gadanki (13.5°N, 79.2°E) on 8 April 2005. The LP detected electron density irregularities, with scale sizes in the range of about 1 m to 1 km, in three height regions: one region in between 69.6 and 72 km and the other two around 75 km and 78 km each having thickness of less than 1 km. The MST radar observations, however, showed two distinct scattering layers, one around 66 km and another around 75 km. The wave number spectra of the in situ observations, except for those of 69.6–72 km, and radar observed spectral parameters clearly suggest that the electron density fluctuations detected by the LP and those responsible for the radar echoes are of turbulence origin. Energy dissipation rates estimated from both rocket‐borne in situ measurements and radar observed spectral width are found to be in the range of 1–70 mWkg −1 . The RMS turbulent velocities estimated from the two observations are found to be <3 m s −1 . Further, the energy dissipation rates and RMS turbulent velocities estimated for the height region of ∼75 km which is common in the in situ and radar data and not reported earlier, are found to be in good agreement with each other. The energy dissipation rates are compared critically with those reported earlier, and the radar‐rocket observations are discussed in the light of current understanding of the low‐latitude mesospheric echoes.