Archive of MSSL Space Plasma Science Highlights

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Seasonal and Temporal Variations of Field‐Aligned Currents and Ground Magnetic Deflections During Substorms

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Figure 3 from Forsyth et al. [2018]. Superposed epoch analysis results with respect to substorm onset of the substorm FACs (SU‐MLT and SD‐MLT) from AMPERE, calculated by removing the median current in the hour before onset. The top and bottom rows show the upward substorm FAC (SU) and downward substorm FAC (SD), respectively, in each MLT sector. As per the above, the results are subdivided into seasons of 90 days centered on the solstices and equinoxes.

Earth is surrounded by electrical currents flowing in space. These currents, which can be 10,000 times greater than domestic electrical supplies, can flow along the Earth's magnetic field and into the upper atmosphere and are linked to aurora. The size of this current depends on atmospheric conditions, with the upper atmosphere being a better conductor when it is sunlit, and the interaction between particles flowing from the Sun and the Earth's magnetic field. During space weather events known as substorms, which happen several times per day on average, the aurora brightens massively and the currents flowing into the upper atmosphere increase. Using data from the Iridium communications satellites, measured these currents during substorms.

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