Abstract. During the MaCWAVE winter campaign in January 2003, layers of enhanced echo power known as PMWE (Polar Mesosphere Winter Echoes) were detected by the ESRAD 52 MHz radar on several occasions. The cause of these echoes is unclear and here we use observations by meteorological and sounding rockets and by lidar to test whether neutral turbulence or aerosol layers might be responsible. PMWE were detected within 30 min of meteorological rocket soundings (falling spheres) on 5 separate days. The observations from the meteorological rockets show that, in most cases, conditions likely to be associated with neutral atmospheric turbulence are not observed at the heights of the PMWE. Observations by instrumented sounding rockets confirm low levels of turbulence and indicate considerable small-scale structure in charge density profiles. Comparison of falling sphere and lidar data, on the other hand, show that any contribution of aerosol scatter to the lidar signal at PMWE heights is less than the detection threshold of about 10%.

On August 9, 1981, a series of three rockets were launched over an air mass thunderstorm off the eastern seaboard of Virginia while simultaneous stratospheric and ground‐based electric field measurements were made. The conductivity was substantially lower at most altitudes than the conductivity profiles used by theoretical models. Direct current electric fields over 80 mV/m were measured as far away as 96 km from the storm in the stratosphere at 23 km altitude. No dc electric fields above 75 km altitude could be identified with the thunderstorm, in agreement with theory. However, vertical current densities over 120 pA/m² were seen well above the classical “electrosphere” (at 50 or 60 km). Frequent dc shifts in the electric field following lightning transients were seen by both balloon and rocket payloads. These dc shifts are clearly identifiable with either cloud‐to‐ground (increases) or intercloud (decreases) lightning flashes.

Abstract. The electrical structure of NLC/PMSE regions was investigated by different rocket-borne in situ probe techniques as part of the DROPPS program. Gerdien condenser measurements of very small mobility values suggest concentrations of positively charged aerosols/dust comparable to the density of more mobile positive ions at PMSE/NLC altitudes. Relative electron density values and associated large-and small-scale vertical structure measured by DC Langmuir probes revealed very deep (by a factor of 50) biteouts in PMSE/NLC regions. These biteouts were seen during strong and weak NLC conditions when PMSEs were either present or absent.

[1] Results from a sounding rocket experiment launched on September 19, 2004 from Kwajalein Atoll, Marshall Islands are reported. A large modulation of the temperature profile in the upper mesosphere was observed with a local maximum at 92 km, 40 K warmer than 2 km below. The temperature gradient between 92 and 102 km was nearadiabatic, suggesting strong mixing. Turbulence was observed in the lower part of the mixed layer, as evidenced by neutral and plasma density fluctuations on both the upleg and downleg portions of the flight. The plasma density gradient was less steep in the mixed region. The turbulent energy dissipation rate was found to be 170 mW/kg. The thermal structure can be described as an upper mesospheric inversion layer, possibly caused by enhanced wave breaking or turbulent heat transport.

The first simultaneous electric field observations performed in the ionosphere and atmosphere over an active nighttime thunderstorm are reported here. In the stratosphere, typical storm‐related dc electric fields were detected from a horizontal distance of ∼100 km, and transient electric fields due to lightning were measured at several different altitudes. In the ionosphere and mesosphere, lightning‐induced transient electric fields in the range of tens of millivolts per meter were detected with rise times at least as fast as 0.2 ms and typical duration of 10–20 ms. The transients had significant components parallel to the magnetic field at 150 km altitude. This implies that either considerable Joule heating occurs or a collective instability is present because of the high drift velocities induced by the transient electric fields. Copious numbers of whistlers were genrated by the storm and were detected above but not below the base of the ionosphere. We present here the outline of a new model for direct whistler wave generation over an active thunderstorm based on these observations. The intensity of the observed two‐hop whistlers implies that they were amplified along their propagation path and suggests that particles were precipitated in both hemispheres.