Fundamental Understanding of Magnetic Reconnection via Spiral CT Scan. VII. Energy Conversion

For the first time, we reveal the distribution of energy conversion (J · E′) around a reconnection X-line, by using the spiral CT scan technique, which is a novel technique analogous to that used in hospitals. This X-line was detected by the Magnetospheric Multiscale mission at the terrestrial magnetopause and has been widely believed to host a non-guide-field reconnection. With the help of such an advanced technique, we find that the energy conversion is strong near the X-point and in the magnetosphere-side inflow region, but is weak in the magnetosheath-side inflow region and at the separatrix. Such distribution is quite similar to the parallel-electric-field distribution, indicating that parallel electric fields may be responsible for the energy conversion. Surprisingly, the magnetic reconnection converts magnetic energy to particle energy in the inflow region (J · E′ > 0) but inversely converts particle energy to magnetic energy near the X-point (J · E′ < 0). This upends the conventional wisdom that magnetic reconnection only converts magnetic energy to particle energy. Quantitatively, we find that the net energy conversion by magnetic reconnection is (B_inflow² − B_outflow²)/2μ₀.