Coverage of a particle instrument in μ-space for a stable magnetic field vector (a) and a fluctuating vector (b). Bottom: colored μ-response for the respectively colored viewing directions of the particle instrument (shown above) corresponding to the stable magnetic field vector shown by the black arrow (same case as part (d) of Fig. 3), or the fluctuating magnetic field vector shown by the black arrow and circle. Top: colored boxes that indicate the parts of μ-space for which the respectively colored viewing directions can obtain a single particle flux value. The colored dashed lines represent the respective nominal μ-values.