A technique is presented for the measurement of magnetic helicity from values of the two-point magnetic-field correlation matrix under the assumption of spatial homogeneity. Knowledge of a single scalar function of space, derivable from the correlation matrix, suffices to determine the magnetic helicity. The technique is illustrated by a report of the first measurement of the magnetic helicity of the solar wind.

• Received 8 May 1981

DOI:https://doi.org/10.1103/PhysRevLett.48.1256