Multiple neutral density measurements in the lower thermosphere with cold-cathode ionization gauges

<p>Cold-cathode ionization gauges were used for rocket-borne measurements of total neutral density and temperature in the aurorally forced lower thermosphere between 90 and 200\&nbsp;km. A commercial gauge was adapted as a low-cost instrument with a spherical antechamber for measurements in molecular flow conditions. Three roll-stabilized payloads on different trajectories each carried two instruments for measurements near the ram flow direction along the respective upleg and downleg segments of a flight path, and six density profiles were obtained within a period of 22\&nbsp;min covering spatial separations up to 200\&nbsp;km. The density profiles were integrated below 125\&nbsp;km to yield temperatures. The mean temperature structure was similar for all six profiles with two mesopause minima near 110 and 101\&nbsp;km, however, for the downleg profiles, the upper minimum was warmer and the lower minimum was colder by 20\textendash30\&nbsp;K indicating significant variability over horizontal scales of 100\textendash200\&nbsp;km. The upper temperature minimum coincided with maximum horizontal winds speeds, exceeding 170\&nbsp;m/s.</p>