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Where can I see the aurora?

Auroras usually occur in ring-shaped areas centered around the magnetic poles of Earth. The complete rings, called the auroral ovals, can only be seen from space. False color picture of the auroral oval in ultraviolet light. The brighter the color, the more intense the aurora.  The crescent of color on the left is from sunlight
scattered over the upper atmosphere. The best places to see the aurora are in Alaska, Canada, and Scandinavia, during the late evening hours.  Resident of the northernmost United States – near the Canadian border – typically see auroras several times a year.  On rare occasions – perhaps once per decade – auroras are visible as far south as Florida or Japan.


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In  this  configuration  the  input  is  applied  between the  base  and  the  collector and  the  output  is  taken  from  the  collector  and  the  emitter.  Here  the  collector  is common to both the input and the output circuits as shown in Fig.

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In  common  collector  configuration  the  input  current  is  the  base current  IB  and  the output current is the emitter current IE. The ratio of change in emitter current to the  change in the base current is called current amplification factor.

It is represented by


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