Editing Space weather (section)

==Models==
Space weather models are simulations of the space weather environment. Models use sets of mathematical equations to describe physical processes.

These models take a limited data set and attempt to describe all or part of the space weather environment in or to predict how weather evolves over time. Early models were heuristic; i.e''., '' they did not directly employ physics. These models take less resources than their more sophisticated descendants.

Later models use physics to account for as many phenomena as possible. No model can yet reliably predict the environment from the surface of the Sun to the bottom of the Earth's ionosphere. Space weather models differ from meteorological models in that the amount of input is vastly smaller.

A significant portion of space weather model research and development in the past two decades has been done as part of the [[outer space#Geospace|Geospace]] Environmental Model (GEM) program of the [[National Science Foundation]]. The two major modeling centers are the Center for Space Environment Modeling (CSEM)<ref>{{Cite web|title = CSEM - Center for Space Environment Modeling|url = http://csem.engin.umich.edu/|website = csem.engin.umich.edu|access-date = 2015-07-24}}</ref> and the Center for Integrated Space weather Modeling (CISM).<ref>{{Cite web|title = CISM // Home|url = http://www.bu.edu/cism/|website = www.bu.edu|access-date = 2015-07-24}}</ref> The [[Community Coordinated Modeling Center]]<ref>{{Cite web|url = http://ccmc.gsfc.nasa.gov/|title = NASA Community Coordinated Modeling Center}}</ref> (CCMC) at the NASA [[Goddard Space Flight Center]] is a facility for coordinating the development and testing of research models, for improving and preparing models for use in space weather prediction and application.<ref>{{cite journal | doi = 10.1029/2011SW000663 | volume=9 | title=Wang-Sheeley-Arge-Enlil Cone Model Transitions to Operations | year=2011 | journal=Space Weather | last1 = Parsons | first1 = Annette| issue=3 | pages=n/a | bibcode=2011SpWea...9.3004P | s2cid=120992652 | url=https://zenodo.org/record/1231301 | doi-access=free }}</ref>

Modeling techniques include (a) [[magnetohydrodynamics]], in which the environment is treated as a fluid, (b) particle in cell, in which non-fluid interactions are handled within a cell and then cells are connected to describe the environment, (c) first principles, in which physical processes are in balance (or equilibrium) with one another, (d) semi-static modeling, in which a statistical or empirical relationship is described, or a combination of multiple methods.