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Last Post 3/10/2006 10:55 AM by Yan Li

sunspot cycles

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Jim Stryder

Basic Member

Posts:105

3/9/2006 10:37 AM
Alejandra (BC) During the solar mimimum, what's the longest period ever seen without sunspots on the sun, i.e., (days,weeks,months)?

Holly Gilbert

New Member

Posts:81

3/10/2006 5:39 AM
Hi Alejandra, I don't know the exact longest period in which there were no observed sunspots, but the Sun has gone through periods of decreased sunspot numbers. Early records of sunspots indicate that the Sun went through a period of inactivity in the late 17th century. Very few sunspots were seen on the Sun from about 1645 to 1715, a time called the "Maunder Minimum", after the English astronomer Edward W. Maunder who studied this unusual time of solar inactivity. This period of inactivity also corresponds to a climatic period called the "Little Ice Age" when rivers that are normally ice-free froze and snow fields remained all year at lower altitudes. The Sun has gone through similar periods of inactivity in the more recent past. Holly

Terry Kucera

Basic Member

Posts:328

3/10/2006 5:41 AM
Hi Alejandra, In recent times the answer to your question is "weeks". I was not sure about that so I went to a page which lists the sunspot number. http://www.ngdc.noaa.gov/...r.html#international I looked at a file that lists the sunspot number since 1944 and found the longest period with zero sunspot number was 37 days in 1996 (the last sunspot minimum). The sunspot number is actually not the same thing as the number of sunspots (they talk about this on that page I mention above), but still, zero sunspot number means no sunspots! There may have been longer periods in times past. There was a period from about 1645 to 1715 called the Maunder Minimum where there were very few sunspots at all (although there were some). The period between sunspots during this time may have been even longer. Cheers, Terry

Yan Li

New Member

Posts:55

3/10/2006 10:55 AM
Hi Alejandra, <!--[endif]--> Perhaps you’d like to first see a plot of the sunspot numbers recorded since far back. http://science.msfc.nasa.gov/ssl/pad/solar/images/ssn_yearly.jpg <!--[endif]--> You can see there is a period of time when the Sun is very inactive during about 1645 and 1700. That period is called the Maunder minimum, when there looked like could be many years going by without a sunspot. The Sun must have been very boring back then. But as you could also see, it seems to be a very special period of time since we have sunspot records. In recent years, things are looking pretty different. Take the last solar minimum, year 1996, as an example, the longest period without any sunspots is something like six weeks. You may also take a look at this NOAA data page for yourself at ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SUNSPOT_NUMBERS/1996 <!--[if !supportEmptyParas]--> Yan <!--[endif]-->