SuperDARN operations Pasha Ponomarenko

Outline Operational principles Antenna design and coverage Pulse sequence and ACF Data processing and presentation

Just to remind: The Main Objective Mapping 2D ionospheric plasma circulation at high latitudes

Operation principles Resolving 2D ionospheric plasma velocities in range-azimuth (horizontal) domain Azimuth: multi-beam pattern Range: pulsed mode (time delay) Line-of-sight Velocity: Doppler shift Velocity vector: receiving echoes from the same areas by different radars (i.e. from different directions) fitting to a velocity model

Phased array: Azimuthal scan SuperDARN: main array: 16 log-periodic antennae interferometer: 4 log-periodic antennae resolution: ~3.5 deg coverage (16 beams): ~54 deg phase shift

Field of view (FoV) Each radar consecutively scans through 16 directions (“beams”) every 1or 2 minutes. Along each beam the returned echoes are sampled at 45-km steps forming 70-75 “range gates” (max. range~3500 km) Total FoV consists of ~1200 range-beam cells

Pulse sequence & complex ACF Radar emits a sequence of 7 or 8 pulses For each range gate a complex autocorrelation function (ACF) is calculated

SuperDARN software: FITACF Experimental ACF ptab[mppul] short mppul Pulse table. ltab[2][mplgs] short 2,mplgs Lag table. pwr0[nrng] float nrng Lag zero power. slist[0-nrng] short 0-nrng List of stored ranges. nlag[0-nrng] short 0-nrng Number of points in the fit. qflg[0-nrng] char 0-nrng Quality of fit flag for ACF. gflg[0-nrng] char 0-nrng Ground scatter flag for ACF. p_l[0-nrng] float 0-nrng Power from lambda fit of ACF. p_l_e[0-nrng] float 0-nrng Power error from lambda fit of ACF. p_s[0-nrng] float 0-nrng Power from sigma fit of ACF.. p_s_e[0-nrng] float 0-nrng Powr error from sigma fit of ACF. v[0-nrng] float 0-nrng Velocity from ACF. v_e[0-nrng] float 0-nrng Velocity error from ACF. w_l[0-nrng] float 0-nrng Spectral width from lambda fit of ACF. w_l_e[0-nrng] float 0-nrng Spectral width error from lambda fit of ACF. w_s[0-nrng] float 0-nrng Spectral width from sigma fit of ACF. w_s_e[0-nrng] float 0-nrng Spectral width error from sigma fit of ACF. sd_l[0-nrng] float 0-nrng Standard deviation of sigma fit. sd_s[0-nrng] float 0-nrng Standard deviation of lambda fit. sd_phi[0-nrng] float 0-nrng Standard deviation of phase fit of ACF. x_qflg[0-nrng] char 0-nrng Quality of fit flag for XCF. x_gflg[0-nrng] char 0-nrng Ground scatter flag for XCF. x_p_l[0-nrng] float 0-nrng Power from lambda fit of XCF. x_p_l_e[0-nrng] float 0-nrng Power error from lambda fit of XCF. x_p_s[0-nrng] float 0-nrng Power from sigma fit of XCF. x_p_s_e[0-nrng] float 0-nrng Power error from sigma fit of XCF. x_v[0-nrng] float 0-nrng Velocity from XCF. x_v_e[0-nrng] float 0-nrng Velocity error from XCF. x_w_l[0-nrng] float 0-nrng Spectral width from lambda fit of XCF. x_w_l_e[0-nrng] float 0-nrng Spectral width error from lambda fit of XCF. x_w_s[0-nrng] float 0-nrng Spectral width from sigma fit of XCF. x_w_s_e[0-nrng] float 0-nrng Spectral width error from sigma fit of XCF. phi0[0-nrng] float 0-nrng Phase determination at lag zero of the ACF. phi0_e[0-nrng] float 0-nrng Phase determination error at lag zero of the ACF. elv[0-nrng] float 0-nrng Angle of arrival estimate. elv_low[0-nrng] float 0-nrng Lowest estimate of angle of arrival. elv_high[0-nrng] float 0-nrng Highest estimat of angle of arrival. x_sd_l[0-nrng] float 0-nrng Standard deviation of lambda fit of XCF. x_sd_s[0-nrng] float 0-nrng Standard deviation of sigma fit of XCF. x_sd_phi[0-nrng] float 0-nrng Standard deviation of phase fit of XCF. FITACF

Main estimated parameters ACF power Signal-to-noise ratio (“power”) [dB] – maximum ACF power Spectral width [m/s] – ACF power decay time Line-of-sight velocity (“velocity”) [m/s] – ACF phase slope ACF phase

Velocity vector measurements Overlapping FoVs provide line-of-sight measuremets from two different directions at the same location They are combined into a 2D velocity vector

Plasma circulation (“convection”) maps Velocity vectors from different radars are combined into a plasma circulation map Electric field distribution is calculated from velocities based on ExB assumption

Plotting data: range-time maps

Plotting data: fan plots

Attention: Software availability! SuperDARN “starter’s kit” that contains ready-to-use IDL routines which have been tested on Chapman: reading fitted data from the standard radar output files into IDL variables range-time plotting plotting “fan” diagrams (maps, coordinate systems etc) PDF files describing SuperDARN data formats/variables/parameters