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 kilometers. 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.

Sunspot region 11944 at a size of 1480MH as seen by the Solar Dynamics Observatory. The Earth has been added for scale.

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 Square kilometers Square Degrees
10 30 million 0.2
100 304 million 2.1
250 760 million 5.2
600 1826 million 12.4
1200 3652 million 24.7

<< Go to previous page

Latest news

Support SpaceWeatherLive.com!

A lot of people come to SpaceWeatherLive to follow the Sun's activity or if there is aurora to be seen, but with more traffic comes higher server costs. Consider a donation if you enjoy SpaceWeatherLive so we can keep the website online!

11%

Space weather facts

Last X-flare:2017/09/10X8.2
Last M-flare:2017/10/20M1.0
Last geomagnetic storm:2020/02/19Kp5 (G1)
Number of spotless days in 2020:38
Current stretch spotless days:24

This day in history*

Solar flares
12014X4.9
22002M1.0
32000C8.6
42004C8.0
52014C5.7
ApG
1200020
2199618G1
3199414
420059
520158
*since 1994

Social networks