Challenges to Understanding the Earth's Ionosphere and Thermosphere

다국어 초록 (Multilingual Abstract)

We discuss, in a limited way, some of the challenges to advancing our understanding and description of the coupled plasma and neutral gas that make up the ionosphere and thermosphere (I‐T). The I‐T is strongly influenced by wave motions of the neutral atmosphere from the lower atmosphere and is coupled to the magnetosphere, which supplies energetic particle precipitation and field‐aligned currents at high latitudes. The resulting plasma dynamics are associated with currents generated by solar heating and upward propagating waves, by heating from energetic particles and electromagnetic energy from the magnetosphere and by the closure of the field‐aligned currents applied at high latitudes. These three contributors to the current are functions of position, magnetic activity, and other variables that must be unraveled to understand how the I‐T responds to coupling from the surrounding regions of geospace. We have captured the challenges to this understanding in four major themes associated with coupling to the lower atmosphere, the generation and flow of currents within the I‐T region, the coupling to the magnetosphere, and the response of the I‐T region reflected in the neutral and plasma density changes. Addressing these challenges requires advances in observing the neutral density, composition, and velocity and simultaneous observations of the plasma density and motions as well as the particles and field‐aligned current describing the magnetospheric energy inputs. Additionally, our modeling capability must advance to include better descriptions of the processes affecting the I‐T region and incorporate coupling to below and above at smaller spatial and temporal scales.
The ionosphere is the region of Earth's upper atmosphere made up of a mixture of charged and neutral gases between approximately 50 and 1,000 miles (80–1,600 km) above the Earth's surface. Sandwiched between the lower atmosphere and the magnetosphere, the ionosphere reacts to weather and climate near the Earth's surface and to eruptions and sunspot activity on the Sun. The ionosphere absorbs the harmful radiation from the Sun and determines the fidelity of all radio communication, navigation, and surveillance transmissions through it. It is part of a complex, coupled system that changes on scales from meters to the planetary radius, and from seconds to decades. Understanding how the behavior of this region is controlled, by internal interactions and by the external regions to which it is coupled, is the preeminent challenge for the next generation of scientists. These challenges in understanding Earth's ionosphere are associated with deciphering the many changes in neutral and plasma density and their relationships to the coupling with the Earth's lower atmosphere, the generation and flow of currents within the region, and the coupling to the magnetosphere. Addressing these challenges requires advances in observing the composition and dynamics of the neutral particles and simultaneous observations of the charged particles, as well as the particles and field‐aligned current describing the coupling of the ionosphere to the magnetosphere. Additionally, our modeling capability must advance to include better descriptions of the processes affecting the ionosphere and thermosphere region and to incorporate coupling with the regions below and above at smaller spatial and temporal scales.


Winds and currents dependent on external drivers and internal processes need improved descriptions
Coupling to the magnetosphere should include hemispheric differences in energy and mass flow
Formation and evolution of multiscale structures require detailed investigation