Mode (electromagnetism)

The mode of electromagnetic systems describes the field pattern of the propagating waves.: 369 

Some of the classifications of electromagnetic modes include;

  • Modes in waveguides and transmission lines. These modes are analogous to the normal modes of vibration in mechanical systems.: A.4 
    • Transverse modes, modes that have at least one of the electric field and magnetic field entirely in a transverse direction.: 52 
      • Transverse electromagnetic mode (TEM), as with a free space plane wave, both the electric field and magnetic field are entirely transverse.
      • Transverse electric (TE) modes, only the electric field is entirely transverse. Also notated as H modes to indicate there is a longitudinal magnetic component.
      • Transverse magnetic (TM) modes, only the magnetic field is entirely transverse. Also notated as E modes to indicate there is a longitudinal electric component.
    • Hybrid electromagnetic (HEM) modes, both the electric and magnetic fields have a component in the longitudinal direction. They can be analysed as a linear superposition of the corresponding TE and TM modes.: 550 
      • HE modes, hybrid modes in which the TE component dominates.
      • EH modes, hybrid modes in which the TM component dominates.
      • Longitudinal-section modes: 294 
        • Longitudinal-section electric (LSE) modes, hybrid modes in which the electric field in one of the transverse directions is zero
        • Longitudinal-section magnetic (LSM) modes, hybrid modes in which the magnetic field in one of the transverse directions is zero
    • The term eigenmode is used both as a synonym for mode: 5.4.3  and as the eigenfunctions in a eigenmode expansion analysis of waveguides.
      • Similarly natural modes arise in the singular expansion method of waveguide analysis and characteristic modes arise in characteristic mode analysis.
  • Modes in other structures
    • Bloch modes, modes of Bloch waves; these occur in periodically repeating structures.: 291 

Mode names are sometimes prefixed with quasi-, meaning that the mode is not quite pure. For instance, quasi-TEM mode has a small component of longitudinal field.: 123 

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