Spatial and temporal variations of the atmospheric sodium layer observed with a steerable laser radar
LASER radar observations of resonance scattering from atmospheric sodium during the night have, on occasions, shown evidence of short term changes in the height distribution1–3. It has been suggested that these changes arise from the movement of a horizontally structured sodium layer, but the measurements have all been limited to the vertical direction, and have provided no direct evidence of a horizontal variation. Evidence of horizontal structure at mesospheric heights has been provided by observations of hydroxyl emissions in the airglow, both from the ground4 and from an aircraft5,6. In addition, the observed fluctuations of intensities and infrared rotational temperatures of the hydroxyl bands have been associated with the passage of atmospheric gravity waves7,8. We report here observations intended to examine the short term and small scale horizontal variations of the sodium layer which might also be associated with such waves.
Inhomogeneities and wavelike variations of the rotational temperature of atmospheric hydroxyl
Abstract Quiet and disturbed variations of the rotational temperature of the hydroxyl emissions of the night sky in band 4-1 are described. Examples are given of wavelike propagation of the disturbances of rotational temperature.
Atmospheric drag effects on the KOMPSAT-1 satellite during geomagnetic superstorms
We examine the atmospheric drag on the low earth-orbiting satellite, KOMPSAT-1 in a sun-synchronous orbit at ~685-km altitude starting in 1999, during a 3-month (October-December) period in 2003. This 3-month interval includes the October 29-30 and November 20 magnetic superstorms and weak to moderate storms. We observed that the daily KOMPSAT-1 drag acceleration transiently responses to transient storm-time disturbances. That is, there is an one-to-one correspondence between the KOMPSAT-1 drag accelerations and the storm events. We find that the drag acceleration correlates strongly with the level of geomagnetic disturbance. This indicates that the trajectory of KOMPSAT-1 is significantly perturbed during extremely disturbed intervals because of atmospheric density increase. The main contributor to the density increase is Joule heating associated with the geomagnetic activity rather than the solar EUV radiation, as reported by previous studies. We suggest that understanding how the upper atmosphere responses to the geomagnetic-associated heating is important to predict space weather impacts on low earth-orbiting satellites.