The miracle of Dunkirk: 40 facts about the famous evacuation. AS ceremonies to commemorate its 75th anniversary begin JAMES MOORE reveals 40 facts about the famous evacuation. 12:59, Thu, May 21, 2015 | UPDATED: 14:33, Thu, May 21, 2015. GETTY. 338,000 troops were rescued from the beaches of Dunkirk in Operation Dynamo.
Sunspots are magnetic regions on the Sun with magnetic field strengths thousands of times stronger than the Earth's magnetic field. Sunspots usually come in groups with two sets of spots. One set will have positive or north magnetic field while the other set will have negative or south magnetic field. The field is strongest in the darker parts of the sunspots - the umbra. The field is weaker and more horizontal in the lighter part - the penumbra. Click on image for larger version.
The relative sunspot number is defined as R = K (10g + s), where g is the number of sunspot groups and s is the total number of distinct spots. The scale factor K (usually less than unity) depends on the observer and is intended to effect the conversion to the scale originated by Wolf.ach isolated cluster of sunspots is termed a sunspot group, and it may consist of one or a large number of distinct spots whose size can range from 10 or more square degrees of the solar surface down to the limit of resolution (e.g., 1/25 square degree).