资源环境科技发展态势分析平台

We investigate the time dependence of electromagnetic-field-to-plasma energy conversion in the electron diffusion region of asymmetric magnetic reconnection. To do so, we consider the terms in Poynting's theorem. In a steady state there is a perfect balance between the divergence of the electromagnetic energy flux del. (S) over right arrow and the conversion between electromagnetic field and particle energy (J) over right arrow . (E) over right arrow. This energy balance is demonstrated with a particle-in-cell simulation of reconnection. We also evaluate each of the terms in Poynting's theorem during an observation of a magnetopause reconnection region by Magnetospheric Multiscale (MMS). We take the equivalence of both sides of Poynting's theorem as an indication that the errors associated with the approximation of each term with MMS data are small. We find that, for this event, balance between (J) over right arrow . (E) over right arrow = -del . (S) over right arrow is only achieved for a small fraction of the energy conversion region at/near the X-point. Magnetic energy was rapidly accumulating on either side of the current sheet at roughly 3 times the predicted energy conversion rate. Furthermore, we find that while (J) over right arrow . (E) over right arrow > 0 and del. (S) over right arrow < 0 are observed, as is expected for reconnection, the energy accumulation is driven by the overcompensation for <(J)over right arrow> . (E) over right arrow by -del . (S) over right arrow > (J) over right arrow . (E) over right arrow. We note that due to the assumptions necessary to do this calculation, the accurate evaluation of del . (S) over right arrow may not be possible for every MMS-observed reconnection event; but, if possible, this is a simple approach to determine if reconnection is or is not in a steady state.