MODIFY SPIDX

        CLIC\MODIFY SPIDX value

    Modify the spectral index of the source as stored in the header. In  SET
    AMPLITUDE  SPIDX mode, the amplitude is corrected by this spectral index
    with respect to the reference frequency. This also updates element 1  of
    the STOKES_SPIDX source-polarization model vector. See STORE POLMODEL.