Observations of the Geminids and Quadrantids using a stratosphere-troposphere radar

Radar observations of the 1996 Geminid and 1997 Quadrantid showers are reported using the CLOVAR stratosphere-troposphere (ST) radar. A method for determining the limiting sensitivity of a radar system using observed number-amplitude data from a single shower is presented, and the result compared with more conventional measurements. This technique is capable of providing very precise measurement of the mass index for a shower in cases where large numbers of echoes are available. The mass index profiles for both showers are presented and found to be U-shaped with a minimum near the time of peak flux. Peak flux values are found to be 0.19 +/- 0.02 meteoroid km(-2) h(-1) at 261.degrees 82 +/- 0.degrees 2 for the Geminids and 0.14 +/- 0.01 meteoroid km(-2) h(-1) at 283.degrees 08 +/- 0.degrees 08 for the Quadrantids to a limiting radio magnitude of 7.7. The locations of maximum are found to coincide with the visually determined position. No significant difference in the location of maximum is detected for either stream over a range of 2 radio magnitudes or in comparison with the visual results. The Geminid radar flux curve is found to be very broad near maximum with a plateau in activity lasting nearly 2 d, while the-visual curve shows a FWHM of 24 +/- 4 h and modest asymmetry with a slow build-up to maximum. The Quadrantids are found to have a sharp maximum following a Gaussian profile to first order with a full width to the 1/e flux positions of 12 h.