We use Glaubers correlation function function as well as the Green functions formalism to investigate, in the case of a dipolar atomic transition, the causal behaviour of the spontaneously emitted electromagnetic field. We also examine the role played by the longitudinal electric field, which is not described in terms of photonic (transverse) degrees of freedom. We predict the existence of a genuinely quantum memory effect at the level of the near field surrounding the atom, which keeps track of the past excitation and emission by the atom.
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