Solar precursors correlating solar physical phenomena with the level of future solar activity are much better indicators of the progress of a broad phase of the solar cycle -- solar minimum -- than forecasting a specific event such as the bottom of a broad solar minimum by observing the statistics of numeric values such as solar flux. Here's an example of how one solar precursor -- spotless day s -- can be used to assess our progress towards solar minimum. We entered the Cycle 24 solar cycle minimum with the onset of eight spotless days in June 2016. We had only 32 spotless days in 2016. We had 15 spotless days in a row in March 2017, followed by relatively infrequent spotless days for the next seven months. The frequency of occurrence of s potless days accelerated in early November 2017 when we had 13 spotless days in a row followed by many more frequent spotless days over the next five months. We had 104 spotless days during 2017. The frequency of spotless accelerated again last month when we had 25 spotless days. W e've already had 54 spotless days during the first 25% of 2018. So where are we in our progress to solar minimum? This chart shows the number of spotless days -- in red -- since the tenth spotless day of the onset of solar minimum in July 2016. Shown in blue are the average numbers of spotless days during sunspot minimums following sunspot cycles similar to cycle 24. This data suggests that we have just begun a period of very frequent spotless days for at least the next two years. http://www.sidc.be/silso/IMAGES/GRAPHICS/spotlessJJ/SC25_month1015.png The next s olar precursor is frequent long periods of spot-free days. We had a 14 day period of spotless days in 2016, 15 in a row in March 2017, 13 in a row in November 2017, and 14 in a row early last month. Long periods of spotless days will become even more frequent a s we go deeper into solar minimum. We'll see another important solar precursor as long periods of spotless days become more frequent. N ew high latitude, opposite polarity Cycle 25 sunspots will begin to appear more frequently , perhaps by late next year. More frequent Cycle 25 sunspots will signal that we're approaching the bottom of the solar minimum phase of the s olar cycle. So what about the intensity of the next solar cycle? An ongoing solar precursor of the intensity of Cycle 25 is the intensity of the solar magnetic fields prior to our current solar minimum. The good news is that the solar magnetic field strength is already slightly stronger than it was prior to the last solar minimum which suggests that Cycle 25 will be somewhat stronger that Cycle 24. 73 Frank W3LPL ----- Original Message ----- From: "Jim Miller" <[email protected]> To: "brian" <[email protected]> Cc: "PVRC" <[email protected]> Sent: Wednesday, April 4, 2018 2:53:26 PM Subject: Re: [PVRC] SFI theoretical minimum? At 68 today and for the past few, we're pretty near the bottom. Thanks all Jim ab3cv On Wed, Apr 4, 2018 at 10:47 AM, brian < [email protected] > wrote: https://wattsupwiththat.com/2008/07/16/sun-in-deep-slumber-107-solar-flux-hits-record-low-value/ Indicates that the theoretical minimum is 67. However, values lower that this have been measured (e.g. lowest ever 64.4 in 1954). The observed values lower than 67 are attributable to the elliptical orbit of the Earth. When the earth is further from the sun, lower measured values than 67 are possible. The article points out that if corrections are made for this orbital distance effect, values lower than 67 don't occur. 73 de Brian/K3KO On 4/4/2018 14:08 PM, Alfred Laun wrote: <blockquote> Jim: Actually SFI=66 is a rule of thumb which I have used for years as being the theoretical minimum possible SFI. I don't know where I originally got that info and indeed, now that you mention it, I may very well be wrong. Indeed during the most recent solar minimum the SFI did plunge to SFI=64 point something on one occasion. And, to quote G3YWX: "The figure for the solar flux can vary from as low as 50 or so to as high as 300." See https://www.arrl.org/files/file/Technology/tis/info/pdf/0209038.pdf I'm sure Frank, W3LPL knows a lot more about this than I do. 73, Fred, K3ZO On Wed, Apr 4, 2018 at 8:56 AM, Jim Miller < [email protected] <mailto: [email protected] >> wrote: Hi Fred You mentioned in one of your recent contest posts that the SFI was near its theoretical minimum of 66. How is that minimum known? Thanks Jim ab3cv ps. always learn something new from your posts! pps. feel free to reply on the reflector if you like < http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient > Virus-free. www.avg.com < http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient > <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> ______________________________________________________________ PVRC mailing list Home: http://mailman.qth.net/mailman/listinfo/pvrc Help: http://mailman.qth.net/mmfaq.htm Post: mailto: [email protected] Message delivered to [email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ PVRC mailing list Home: http://mailman.qth.net/mailman/listinfo/pvrc Help: http://mailman.qth.net/mmfaq.htm Post: mailto: [email protected] Message delivered to [email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html </blockquote> ______________________________________________________________ PVRC mailing list Home: http://mailman.qth.net/mailman/listinfo/pvrc Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] Message delivered to [email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html _________________ Topband Reflector Archives - http://www.contesting.com/_topband
