Abstract
Ionospheric outflow supplies nearly all of the heavy ions observed
within the magnetosphere, as well as a significant fraction of the
proton density. While much is known about upflow and outflow
energization processes, the full global pattern of outflow and its
evolution is only known statistically or through numerical modeling.
Because of the dominant role of heavy ions in several key physical
processes, this unknown nature of the full outflow pattern leads to
significant uncertainty in understanding geospace dynamics, especially
surrounding storm intervals. That is, global models risk not accurately
reproducing the main features of intense space storms because the amount
of ionospheric outflow is poorly specified and thus magnetospheric
composition and mass loading could be ill-defined. This study defines a
potential mission to observe ionospheric outflow from several platforms,
allowing for a reasonable and sufficient reconstruction of the full
outflow pattern on an orbital cadence. An observing system simulation
experiment is conducted, revealing that four well-placed satellites are
sufficient for reasonably accurate outflow reconstructions. The science
scope of this mission could include the following: reveal the global
structure of ionospheric outflow; relate outflow patterns to geomagnetic
activity level; and determine the spatial and temporal nature of outflow
composition. The science objectives could be focused to be achieved with
minimal instrumentation (only a low-energy ion spectrometer to obtain
outflow reconstructions) or with a larger scientific scope by including
contextual instrumentation. Note that the upcoming Geospace Dynamics
Constellation mission will observe upwelling but not ionospheric
outflow.