Neutral winds above 200 km at high latitudes

Abstract

Electrically neutral, luminous clouds are a by‐product of chemical releases conducted to create barium ion clouds for the measurement of electric fields. Wind measurements provided by the motions of these clouds are particularly valuable in that the motions can be directly compared with convective ion drift motions to test the importance of ion drag forces. Motion from multiple releases between 200 and 300 km from 15 rockets launched from four high‐latitude locations is analyzed in this paper. The observations in the evening and midnight hours at magnetic latitudes of ≥65° strongly suggest that in these regions ion drag is the dominant force in driving neutral winds between 200 and 300 km. This conclusion is based on both the agreement between ion and neutral drift directions and the fact that there are distinct changes in the wind associated with (a) the reversal in east‐west ion drift at the Harang discontinuity, and (b) the transition from auroral belt sunward ion drift and polar cap antisolar ion drift. In the morning sector it is evident that neutral wind observations cannot be directly interpreted in terms of ion drag; other factors must be considered, such as inertial effects from ion drag, a lack of sufficient ionization for strong coupling of ion neutral motions, and wind forces other than ion drag forces.

Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(<sup>1</sup>D) dayglow measurements from Chile

“…This heating also causes an upwelling of the neutral species over the auroral oval, which generates a large wave that is capable of propagating to the magnetic equator in a few hours (Mayr et al, 1978;Prolss, 1993). There are ample evidences of an increase in the neutral temperature and winds at low latitudes during magnetic storms (Mayr and Volland, 1973;Meriwether et al, 1973;Mayr et al, 1978;Prolss, 1980;Burrage et al, 1992;Prolss, 1993;Burns et al, 1995;Fuller-Rowell et al, 1996;Pant and Sridharan, 1998;Fujiwara et al, 1996;Emmert et al, 2001). The thermospheric winds and composition changes are intimately coupled and as a consequence, the F-region electron densities also change accordingly.…”

Interpretation of ionospheric F-region structures in the vicinity of ionisation troughs observed by satellite radio tomography

“…The shape of the precipitation zone as well as the particle energies were taken from the statistical models by Hardy et al (1985Hardy et al ( , 1989. The horizontal component of the neutral wind was consistent with the neutral wind measurements by Meriwether et al (1973) at 300 km altitude. It should be noted that the irregularity located on the trough poleside wall of the calculated N e pattern (bottom panel of Fig.…”

Simulation study of the large-scale modification of the mid-latitude F-layer by HF radio waves with different powers

“…It appears that this level is inappropriately high. However, the fact is that the utilized neutral wind distribution, obtained using the data presented in the study of Meriwether et al (1973), provides a meridional component of the neutral wind velocity of about 165 m s −1 at F-layer altitudes near the considered geographic point, with the direction of the velocity being equatorward. It is known that an equatorward neutral wind ought to raise the F2-layer electron concentration peak.…”

“…This distribution is obtained by analogy with the study of Mingaleva and Mingalev (1996), with the horizontal distribution of the neutral wind at 300 km, taken from Meriwether et al (1973), having been applied.…”