Making sense of SuperDARN elevation: Phase offset and variance Pasha Ponomarenko, Jan Wiid, Sasha Koustov, and Jean-Pierre St.-Maurice University of Saskatchewan, CANADA 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

SuperDARN Workshop, 29 May - 3June 2011, Hanover, US Abstract The vertical angle of arrival of HF signals contains very important information about the propagation modes and ionospheric conditions. However, despite being routinely registered by SuperDARN radars, elevation angles are rarely utilised. The main reason for that is the apparent unreliability of these data, which frequently appear to be unrealistic. At SuperDARN’2010 we attributed the problem to an inadequate phase calibration that fails to account for certain phase shifts in the radar hardware. However, a following detailed analysis of the experimental data and statistical modelling revealed that the presence of “strange” elevation components could be fully explained by accounting for the statistical distribution of phase fitting errors. In essence, a combination of this distribution with the very non-linear phase-elevation relationship leads to a two-pi wrap-around of the phase that results in an artificial population of echoes at very high elevation angles. 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

SuperDARN Workshop, 29 May - 3June 2011, Hanover, US Outline Introduction Apparent problems Phase calibration Fitting error effects Conclusions 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

Definition and importance Elevation angle – vertical angle of arrival of HF signal Diagnostic importance: HF propagation mode ionospheric plasma density (Secant Law) n <1 n = 1 h x 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

SuperDARN Interferometry  d' 2π max Ψmax 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

Elevation vs phase shift 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

Suspiciously high values 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

Split phase distribution? 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

All ranges @ multiple frequencies 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

SuperDARN Workshop, 29 May - 3June 2011, Hanover, US Phase offset? 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

SuperDARN Workshop, 29 May - 3June 2011, Hanover, US Phase calibration 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

SuperDARN Workshop, 29 May - 3June 2011, Hanover, US Calibrated elevation 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

Still does not look right... 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

What about phase fitting errors?  0 Δ σ  31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

One-sigma fitting error from data median  8 deg mean  6 deg 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

Modelling: phase variance effect 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

SuperDARN Workshop, 29 May - 3June 2011, Hanover, US So, SOME flipping is OK! Calibrated Raw 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

SuperDARN Workshop, 29 May - 3June 2011, Hanover, US Concluisons If after phase calibration the maximum of the phase distribution at any given range does not flip over to the high elevation end, the elevation data should be OK. Now, how can we utilise elevation? See the follow-up talk on Wednesday! 31 December, 2018 SuperDARN Workshop, 29 May - 3June 2011, Hanover, US