| Just as the weather at the surface of the Earth affects our everyday lives so too do similar variations in pressure, density and temperature in the upper atmosphere. While these do not affect us directly they do impact many space systems that we either rely on now or will rely on in the future. Upper atmosphere pressures may change by a factor of 100. Large space vehicles like the space station and the shuttle may have their orbits significantly perturbed by changes in the atmospheric density |  |  | And at very high altitudes, particles with 100's of kilovolts of energy may suddenly be produced. They can penetrate the circuitry of multi-million dollar communication satellites causing sometimes irreparable damage. | | As activity on the sun changes the magnetospheric cavity changes in shape and volume, and the charged particles within it change their energy and their motion. Unfortunately these internal changes are not directly proportional to the external changes due to many variable internal time constants. That is to say the system is highly non-linear. Presently we cannot predict when, where, or how these changes will occur because we do not understand all the relevant time constants for the physical processes. |  |  |  | The Earth's magnetic field has a dramatic influence on the upper atmosphere. | | High latitudes (where the magnetic field is almost vertical) respond quite differently from low latitudes (where the magnetic field is almost horizontal). | | High latitudes respond rather directly to inputs from the solar wind while low latitudes respond to internally generated disturbances that are weakly modulated by the solar wind. | | Response times for the charged an neutral gases are quite different but influence each other via collisions. | | | Changes in the charged particle densities can affect the propagation of radio signals through the atmosphere. Global cellular telephone systems may be compromised when charged particle populations in the upper atmosphere become irregular | | 
| Space weather is produced by an interaction between the Sun and the Earth that is quite different from the heat and light that we usually experience. This interaction involves the magnetic fields of the Earth and the Sun. The sun, shown in the upper right image, is a highly active star that ejects streams of charged particles that move at supersonic speeds toward the Earth. This stream is called the solar wind. Together these interactions produce a large magnetic cavity called the magnetosphere within which charged particles are trapped and may circulate. This cavity is illustrated in the upper left image. | | Before we can predict Space Weather, we must first describe the many basic states of the upper atmosphere (similar to asking if it is snowing, raining, sunny, cloudy, windy etc.). Then we must understand the interactions between the ionosphere, the upper atmosphere and the magnetosphere, that can exist during these states and which may act to change the state. There are many existing space data sets that can be used to start these studies. Data like those shown to the left are taken from multiple instruments on the Dynamics Explorer satellites and are used to describe the behavior of the magnetosphere, the ionosphere and the upper atmosphere. |  | At UTD we have already learned quite a bit about the ionosphere and upper atmosphere from these data.  The challenge is to discover the temporal and spatial scales over which important physical processes are most effective. That was just a simple introduction to a rather complex topic. There are other places you can go to learn more about the details. AT UTD we are working in some specialized areas that you can get to here.
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