A snapshot of the particle environment in the Earth’s magnetosphere

During the Juice (Jupiter Icy Moons Explorer) flyby of Earth in August 2024, the spacecraft traversed the magnetosphere in the time span of about 12 hours. The mass spectrometer Jovian Plasma Dynamics and Composition Analyzer (JDC) has the capability to observe, within a hemisphere, electrons in the energy range of a few eV/q - 35 keV/q, and positive and negative ions with masses between 1 and 70 amu, in the energy range of a few eV/q - 35 keV/q.

The measurements of JDC enabled us to characterize the state of the Earth’s magnetosphere at this point in time. The spacecraft passed through all key plasma domains and boundaries and the data taken provide a semi-instantaneous view of the magnetosphere. The plasmasphere, the ring current, the radiation belt and the magnetosheath are probed.  Multiple crossings of the magnetopause are seen as well as foreshock phenomena upstream of the bow shock. The plasma populations recorded are compared to the typical plasma parameters characterizing each region, taking upstream conditions and geomagnetic indices into account. The observations of the radiation belt are compared with a location-dependent radiation belt model. The data shows the excellent performance of the versatile mass spectrometer and clearly shows how an interplanetary mission can contribute to magnetospheric science.