Super Dual Auroral Radar Network observations of fluctuations in the spectral distribution of near range meteor echoes in the upper mesosphere and lower thermosphere

Abstract

Abstract. The Doppler shifts of meteor echoes measured by the SuperDARN HF radar network have been used in several studies to observe neutral winds in the upper mesosphere and lower thermosphere region. In the absence of accurate height information for individual meteors, it has been necessary to assume a statistical mean meteor layer where the variations in altitude were not correlated to changes in the horizontal winds. Observations of spectral width distribution variations made by the radars allow an independent determination of the systematic error in the height. We have investigated the dependence of this distribution on a number of factors including the radar geometry, diurnal and seasonal cycles, variations in solar UV irradiance and geomagnetic activity.Changes in the altitude of the mean meteor layer observed at different radar ranges provide us with some insight into the structure of the upper mesosphere and the lower thermosphere within which the meteors are being ablated. An examination of the spectral widths, as measured by the CUT-LASS Finland radar, in the days preceding and following a Storm Sudden Commencement in April 1997, illustrates how the spectral properties of the observed region can be affected. The variations in the widths were consistent with model calculations of the changes to the temperature profile over this interval. Further refinements in the determination of the spectral width are outlined for future experiments.

A decade of the Super Dual Auroral Radar Network (SuperDARN): scientific achievements, new techniques and future directions

“…Arnold et al (2001) examined the spectral width of meteor backscatter echoes and attempted to find a relationship with other geophysical quantities. It was found that the spectral width increased with range from the radar, which indicated a small increase in altitude with range.…”

Comparison of D-region Doppler drift winds measured by the SuperDARN Finland HF radar over an annual cycle using the Kiruna VHF meteor radar

“…Hall et al (1997) first suggested the use of spectral width information to estimate the mean height of the measurements, as this quantity is related to the ambipolar diffusion rate of the meteor trail. Arnold et al (2001) demonstrated that the spectral width parameter provided considerable information about the response of the meteor layer to changing atmospheric conditions. Higher horizontal resolution in the range gates from 45 to 15 km should improve matters during special meteor observing campaigns, but the number of days when the radars could operate in this mode would be limited to only a few days per month (Hussey et al, 2000).…”

“…Ionospheric echoes of non-meteor origins can have spectral widths of up to 1000 ms −1 . In Arnold et al (2001) the limits were set at ±50 ms −1 for the line-of-sight velocities and 50 ms −1 for the spectral width. However, there re- main instances when non-meteor ionospheric scatter could be mistaken for meteor trails.…”

“…The approach adopted by Hall et al (1997) for observations with the HF radars was to reject echo returns from beyond the fifth range gate (360 km from the radar) and a Doppler velocity greater than ±200 ms −1 . The spectral width parameter was found to be related to the ambipolar diffusion which is itself strongly related to atmospheric temperature, pressure and the neutral-ion collision frequency (see, for example, Arnold et al, 2001). This criterion provided qualitatively reasonable results.…”

Stereo CUTLASS - A new capability for the SuperDARN HF radars

“…Makarevitch et al, 2002), the investigation of atmospheric gravity waves (e.g. Bristow et al, 1994;Arnold et al, 1998), the derivation of neutral winds from the scatter from ionisation trails of meteors (Hall et al, 1997;Arnold et al, 2001) and the study of artificially generated irregularities using the high power radio wave transmitter, or heater, at Tromsø Yeoman et al, 1997). Considerable effort has been placed recently in the use of sophisticated analysis techniques to provide the global convection pattern at a time resolution of typically 2 min (Ruohoniemi and Baker, 1998), as well as developing a near-real time capability for Space Weather purposes (e.g.…”