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Magnetic Clouds

When sigmoids and filaments erupt and carry magnetic field lines along with them, they form what are known as magnetic clouds. These magnetic clouds are characterized by a rise in magnetic field magnitude, a decrease in radial temperature and ion density and a smooth rotation of the magnetic field through about 180 degrees in latitude. These features can be seen in the graphs to the left. The beginning and end of the cloud are denoted by the vertical dashed lines and the red lines are a best fit to the data. The graph of |B| shows the rise in magnetic field magnitude. The graph of theta displays the smooth rotation in latitude (theta represents the inclination of the magnetic cloud to the ecliptic). The graph of phi displays the change in longitude. The graph of Vth displays the drop in radial temperature. The graph of Vsw displays the decline in solar wind speed. The graph of np displays the decline in ion density. The graph of Dst shows the change in magnetic storm strength as the cloud impacts Earth's magnetic field.

Magnetic Storms

If a magnetic cloud does reach Earth, it interacts with our magnetic field, sometimes causing major disturbances in our magnetosphere, known as geomagnetic storms. A magnetic storm can have disastrous affects on communications, power grids, satellites and astronauts working in space, but is also the cause for the beautiful arorae seen near the poles. The image to the right illustrates several affects caused by a magnetic storm. A large magnetic storm can generate five tera watts of power. That is equivlent to the power capacity of the United States.

A magnetic storm can induce current in power lines and pipes in the ground, causing large-scale power outages, as well as deform our magnetic field enough to leave satellites vulnerable to the harsh the space environment and possibly destroy them. For these reasons, we hope to be able to predict strong magnetic storms before the eruptions that create the magnetic clouds even occur. That way, when we see a structure on the disk of the sun that we know often produces magnetic clouds that cause strong magnetic storms, we can shut down satellites and powergrids before any damage is done to them.

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