The outer boundary of the Earth's magnetosphere forms a barrier that prevents large amounts of energy, particles, and momentum carried by the solar wind from entering the magnetosphere. This barrier is not impenetrable. By a sequence of complex processes that are still incompletely understood, part of the solar wind's particle and energy content penetrates into the Earth's space environment. Strong electric fields and currents are generated and induced within the magnetosphere, the ionosphere, and the Earth's surface. Our present knowledge of the magnetospheric phenomena basic to space weather prediction and forecasting is quite rudimentary.
Models exist, but they often rely on many free parameters that can be adjusted somewhat arbitrarily.
Simulations need to be three-dimensional, cover an immense volume, and include processes occurring over multiple scale sizes. An artist's conception of the magnetosphere showing magnetic field lines that connect to the aurora in the Earth's polar region. The ionosphere and neutral atmosphere are important to space weather, not only because they are regions where adverse effects commonly occur, but also because they are strongly coupled to each other and to other regions of space. Both the ionosphere and neutral atmosphere vary significantly in response to changing solar energy input on time scales of days to years. Understanding the dynamics of the neutral atmosphere is critical to the development of models that adequately account for many effects, including low-orbit satellite drag.