# How does the energy transfer in the near field of an antenna work?

Answering the question What is the relation between electromagnetic wave and photon? I wrote

The EM radiation of an antenna is measurable and it was found out that the nearfield of an antenna has two components, an electric field component and a magnetic field component. This two components get converted in each other, the induce each other.

Rob commented

@HolgerFiedler If the fields are a quarter-turn out of phase, the average value for the Poynting vector is zero and the wave is not transmitting any energy.

How does the energy transfer in the near field of an antenna work? And how does a standing EM wave inside a box work?

• Related: Phase Alignment in EM Waves – Alfred Centauri Dec 18 '16 at 13:08
• @AlfredCentauri In the not edited version of the question it was ask about the Pointing vector and EM radiation. In the related question you suggest is nothing said about Pointing vector. More interesting is the deleted link to physics.stackexchange.com/questions/90646/… – HolgerFiedler Dec 18 '16 at 13:44
• @AlfredCentauri I think the Pointing vector says something about the average strength of the EM wave but nothing about the strength at one moment of the period between 0 and 2Pi of this wave. – HolgerFiedler Dec 18 '16 at 14:04
• Holger, in my answer, I quoted equations from Jackson that, if I'm not mistaken, are relevant to your question "How does the energy transfer in the near field of an antenna work?". See that there are three terms with different dependence on $r$. See that, in the near field, the dominant terms are in quadrature and so the power is reactive. To make the circuit analogy, an AC source driving a purely reactive load, e.g., a capacitor, sources power half of the time and sinks power the other half; the energy 'sloshes' back and forth between source and load. – Alfred Centauri Dec 18 '16 at 14:48