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ephemeral region (EFR)
An area of the Sun where a magnetic dipole, or flux tube, surfaces on the disk and eventually produces a bipolar sunspot group. In H-alpha, an EFR usually appears as a small oval area of bright plage (typically about 7,000 km across) and often contains a series of short-lived narrow fibrils, known as an arch filament system, running roughly from one end of the dipole to the other. Each pole of an EFR is often marked by pores or small developing sunspots. Surges or even small solar flares can sometimes occur in EFRs.
Related category
• SOLAR TOPICS
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