How do you determine the size of a sunspot region?
The area of sunspot groups is expressed in "millionths of a solar hemisphere" (MH), with 1000MH corresponding to 3.043,7 million square kilometres.
This means that a sunspot group which has an area coverage of 1870MH covers 0.187% of the earth-facing solar surface. Most sunspot groups cover an area
about the size of the surface of the Earth (which equals almost 170MH) but the larger sunspot groups can easily reach 1000MH or even much more than that.
Image: Sunspot region 11944 at a size of 1480MH as seen by the Solar Dynamics Observatory. The Earth has been added for scale.
Solar area conversion table
|Millionths of Hemisphere
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Current data suggest that it is not possible to see aurora now at middle latitudes
Active geomagnetic conditions expected
The solar wind speed is currently moderately high (582.1 km/sec.)
Sunday, 20 August 2017 - 07:31 UTC
Monday, 14 August 2017 - 18:56 UTC
Monday, 14 August 2017 - 13:21 UTC
Today's space weather
|Predicted Kp max
|M-class solar flare
|X-class solar flare
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Space weather facts
|Last geomagnetic storm:||2017/08/20||Kp5 (G1)|
|Number of spotless days in 2017:||56|
|Last spotless day:||2017/08/01|
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