The Earth’s magnetosphere is filled by particles from two sources: the solar wind and the ionosphere. Ionospheric ions are initially cold and contain He+ and O+, in addition to to H+. Depending on their initial magnetic latitude and local time, and the state of the magnetosphere, they may contribute to the plasmasphere, the plasma sheet, the ring current, the warm plasma cloak etc. Depending on which path they follow in the magnetosphere, some of these ionospheric ions remain cold when they reach the two key reconnection regions: the Earth’s magnetopause and the plasma sheet in the tail. In this presentation, we will first review previous statistical works that quantify the number of cold/ionospheric ions near these two regions. Several works have attempted to quantify these populations, but they are inherently difficult to characterize due to their low energy, often below the spacecraft potential. We will also discuss the impacts they have on the magnetic reconnection process. Ionospheric ions mass-load the regions where reconnection takes place and change the characteristic Alfven speed, resulting in a smaller reconnection electric field. They also take a portion of the energy that is imparted to particles, affecting the energy budget of magnetic reconnection. Finally, they introduce new length and time scales, associated to their gyroradius and gyroperiod. We will discuss what are the implications of these impacts for the evolution of the magnetosphere – solar wind interactions.

During periods of strong magnetic activity, cold dense plasma from the plasmasphere typically forms a plume extending towards the dayside magnetopause, eventually reaching it. In this work, we present a large-scale two-dimensional fully kinetic Particle-In-Cell simulation of a reconnecting magnetopause hit by a propagating plasmaspheric plume. We observe three main phases: before the plume arrives at the magnetopause, a transient phase where the system reshapes because of the new inflow conditions, and the full interaction when the plume is well engulfed in the reconnection site. We show the evolution of the magnetopause’s dynamics subjected to the modification of the inflowing plasma. Our main result is that the change in the plasma temperature (cold protons in the plume) have no effects on the magnetic reconnection rate, which on average depends only on the inflowing magnetic field and total ion density, before, during and after the impact.

Ionospheric ions (mainly H+, He+ and O+) escape from the ionosphere and populate the Earth’s magnetosphere. Their thermal energies are usually low when they first escape the ionosphere, typically a few eV to tens of eV, but are energized in their journey through the magnetosphere. The ionospheric population is variable, and it makes significant contributions to the magnetospheric mass density in key regions where magnetic reconnection is at work. Solar wind - magnetosphere coupling occurs primarily via magnetic reconnection, a key plasma process that enables transfer of mass and energy into the near-Earth space environment. Reconnection leads to the triggering of magnetospheric storms, aurorae, energetic particle precipitation and a host of other magnetospheric phenomena. Several works in the last decades have attempted to statistically quantify the amount of ionospheric plasma supplied to the magnetosphere, including the two key regions where magnetic reconnection proceeds: the dayside magnetopause and the magnetotail. Recent in-situ observations by the Magnetospheric Multiscale spacecraft and associated modelling have advanced our current understanding of how ionospheric ions alter the magnetic reconnection process at meso- and small-scales, including its onset and efficiency. This article compiles the current understanding of the ionospheric plasma supply to the magnetosphere. It reviews both the quantification of these sources and their effects on the process of magnetic reconnection. It also provides a global description of how the ionospheric ion contribution modifies the way the solar wind couples to the Earth’s magnetosphere and how these ions modify the global dynamics of the near-Earth space environment.

In situ spacecraft missions are powerful assets to study processes that occur in space plasmas. One of their main limitations, however, is extrapolating such local measurements to the global scales of the system. To overcome this problem at least partially, multi-point measurements can be used. There are several multi-spacecraft missions currently operating in the Earth’s magnetosphere, and the simultaneous use of the data collected by them provides new insights into the large-scale properties and evolution of magnetospheric plasma processes. In this work, we focus on studying the Earth’s magnetopause using a conjunction between the MMS and Cluster fleets, when both missions skimmed the magnetopause for several hours at distant locations during radial IMF conditions. The observed magnetopause positions as a function of the evolving solar wind conditions and compared to model predictions of the magnetopause. We observe an inflation of the magnetosphere (˜0.7 RE), consistent with magnetosheath pressure decrease during radial IMF conditions, which is less pronounced on the flank (< 0.2 RE). There is observational evidence of magnetic reconnection in the subsolar region for the whole encounter, and in the dusk flank for the last portion of the encounter, suggesting that reconnection was extending more than 15 RE. However, reconnection jets were not always observed, suggesting that reconnection was patchy, intermittent or both. Shear flows reduce the reconnection rate up to ˜30% in the dusk flank according to predictions, and the plasma ß enhancement in the magnetosheath during radial IMF favors reconnection suppression by the diamagnetic drift.