Closed path in a high-frequency electromagnetic field. A high-frequency time-harmonic electromagnetic field exists in a lossy medium. The current density vector in the medium is J, the electric flux density vector is D, and the magnetic flux density vector is B. The line integral of the magnetic field intensity vector, H, along an arbitrary planar contour (closed path) in the medium equals the flux of the following vector through a flat surface spanned over the contour:_________