Abstract | Magnetic reconnection at the Earth’s dayside magnetopause involves ion populations from both the magnetosheath and magnetosphere. The magnetosphere often contains a cold ion population. This population originates from the ionosphere (generally the plasmaspheric plume) and is not always detectable by particle instruments due to its low energy, despite having an important contribution to the total ion density. In particular, the presence of cold ions at the magnetopause is common in the equatorial plane where the new Magnetospheric Multiscale mission operates. We present 2D fully kinetic simulations of asymmetric magnetic reconnection with same global quantities for all ions taken into account, but different magnetosphere populations. The comparison of simulations with and without cold ions suggests that these directly impact signatures recently suggested as good markers of the X line region, such as a normal electric field shoulder. Our simulations also show a drastic fall in cold ion density near the X line, to the point that almost none of them actually reach the the X-line itself. Such effects are to be taken into account when analyzing in situ measurements. |
