1. Sunspots and Solar Cycles: What might we expect from Cycle 25
Parker Solar Probe
KD8DZ September 2019

3. Corona during a solar eclipse

4. Sunspot Group

5. A Brief History of Sunspot Observations
800 BC Chinese observations recorded in the Book of Changes.
364 BC First deliberate observation by Chinese astronomer Gan De in his star catalogue. Imperial reported regular observations.
300 BC, First mention of sunspots in the west, Greek astronomer, Theophrastus, a student of Plato and Aristotle.
1610 English astronomer Thomas Harriot (Harriot was also the first astronomer to observe a Venus Transit).
1611 German astronomers Johannes and David Fabricius first to publish results about the same time Galileo observed the moons of Jupiter. He had been showing sunspots by projecting on to a white surface using a telescope.
Samuel Schwabe investigated the cyclic nature of sunspots.
1875 Rudolf Wolf created a sunspot number formulation to compare observations of different astronomers.
And many others…
First telescopic observations of sunspots.

6. Sunspot activity over longer time periods
Sunspot Observations and cycles
400 years of cycles
Butterfly patterns
Sunspot activity over longer time periods

7. The Solar Cycle
Sunspot activity waxes and wanes over approximately eleven year period.
28-year period (1645–1715)
Carbon 14 analysis of organic material is an indication of sunspot activity. C14 is caused by the impact of cosmic rays on N14 in the atmosphere. Cosmic rays produce free neutrons. n+N14 = C14(6P+8n) + H(1P) C14 halflife = 5700 years.
Samuel Schwabe begins serious observations of sunspots and
1875 Rudolf Wolf created a sunspot number formulation to compare observations
of different astronomers.

8. Note that the butterfly pattern indicates the position of sunspots on the sun as a function of time. Spot begin forming at high latitudes and over time the formation slowly occurs at lower latitudes.
Note that the butterfly pattern is not completed for the current cycle.

9. Estimate of Solar activity over about 7000 years…
Estimate based on C14 in organic material.

10. Visibility of sunspots
Sunspots appear darker than the surrounding solar photosphere due to their lower temperature about °C, contrasted with the 5500 °C of the observable surrounding photosphere. Magnetic fields emanating from the spots constrain upwelling of hotter gases and thus appear darker.
Lifecycle
Spots last for a few days to as long as months and may expand or contract over time. They are manifestations of magnetic flux tubes that penetrate the surface of the sun caused by the winding up of magnetic field due to differential rotation of the sun. Solar rotation varies with latitude. Fastest at the equator, approximately days and slowest at the poles, almost 38 days
Hotter gases surround the spots which are cooler. Magnetic fields that poke out of the spots constrain the flux of hot gases from within the sun.

11. Sunspot Magnetic Properties define a longer 22 year cycle.
Sunspots begin appearing at higher latitudes at the beginning of a cycle and as the cycle continues, appear progressively at lower latitudes. The sunspot groups form in pairs with leading and trailing spots having opposite magnetic polarities.
The polarities in northern and southern hemispheres are opposite.
In preceding or succeeding cycles, the polarities reverse.
For example, if the polarities in the northern hemisphere of the sun have leading spots which are north magnetic poles, then the leading spot in the southern hemisphere is a south magnetic pole. In the next cycle, the polarities are reversed.

12. How do we know that the about the magnetic properties of sunspots
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In 1908, Georges Ellery Hale used the Zeeman effect with a modified spectrohelioscope to establish that sunspots have strong, concentrated magnetic fields.
Diagram 1, illustrates the magnetically-induced Zeeman splitting in the spectrum of a sunspot.
Diagram 2, illustrates Hale's polarity laws, which present evidence for the existence of a well-organized large-scale magnetic field in the solar interior that cyclically changes polarity every 11 years or so.
Subsequent work demonstrated a strong tendency for east-west alignment of magnetic polarities in sunspots, with mirror symmetry across the solar equator; and that the polarity in each hemisphere switched orientation from one sunspot cycle to the next. This systematic property of sunspot magnetic fields is now commonly referred to as the "Hale–Nicholson law", or in many cases simply "Hale's law." The pressure provided by such strong magnetic fields would also lead naturally to the lower temperatures observed within the sunspots, as compared to the photosphere.
In the following decade Hale and collaborators went on to show that large sunspots pairs almost always show:
the same magnetic polarity pattern in each solar hemisphere,
the opposite polarity patterns between the North and South solar hemispheres, and
a reversal of polarity patterns from one sunspot cycle to the next, indicating that the physical magnetic cycle has a period of twice the sunspot cycle period.
These empirical observations have stood the test of time and are since known as Hale's polarity Laws. Their physical origin is now known to originate with the operation of a large scale hydromagnetic dynamo within the solar interior, although the details of the process are far from adequately understood. Because the sun's dynamo generated magnetic field is ultimately responsible for all manifestations of solar activity (flares, coronal mass ejections, etc.), to this day solar dynamo modeling remains a very active area of research in solar physics.
Bibliography: G.E. Hale, F. Ellerman, S.B. Nicholson, and A.H.Joy, The Astrophysical Journal, vol. 49, pps. 153–178.
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How do we know that the about the magnetic properties of sunspots
The Zeeman effect in sunspots demonstrates the magnetic nature of sunspots and its polarity. The spectrum of the Fe I Å iron line taken by George Ellery Hale showing the magnetic Zeeman splitting/broadening. The same spectra line not in a magnetic field would not show the splitting of the line.
sunspot 1

13. Magnetograms Line of sight fields Magnetograms determine
Stanford Solar Center
Magnetograms determine
Sunspot polarity. Has to do
with the polarized light
from the spot.
Line of sight fields
South polarity magnetic fields
(black) point into the sun
and North polarity magnetic fields (white) point out of the sun.
The light from a sunspot is polarized by the magnetic field acting on the Fe ion in the spot.

15. A solar eruptive prominence as seen in extreme UV light on March 30, 2010 with Earth superimposed for a sense of scale. Credit: NASA/SDO
The ionize material ejected in a solar prominence follows the magnetic lines.

16. Sunspot numbers are calculated by first counting the number of groups and then the number of individual spots.
The “sunspot number” is then given by the sum of the number of individual sunspots and ten times the number of groups. Since most sunspot groups have, on average about ten spots, this formula for counting sunspots gives reliable numbers even when the observing conditions are less than ideal and small spots are hard to see.
R = k (10g + s)
R = sunspot number, g number of groups, s number of individual spots and k an atmospheric factor.
Highest smoothed number was 201 for cycle 19.

18. The 10.7 cm solar radio flux is an excellent indicator of solar activity and correlates with sunspot activity. F10.7 has been measured consistently in Canada since 1947
10.7 cm (2800 MHz) radio emission from the sun in solar flux units (sfu) feom the Penticton Radio Observatory in British Columbia, Canada

19. Dominion Radio Astrophysical Observatory
Penticton, British Columbia, Canada

20. There is a relationship between smoothed sunspot number and the 10
There is a relationship between smoothed sunspot number and the 10.7 cm solar flux reported daily on various sources.

21. Take Away
10.7 Solar Flux is directly related to the solar magnetic activity. That is Sunspots.
In addition to the continuous measurements made by 2 dedicated radio telescopes at the Dominion Radio Astrophysical Observatory and reported on the web at 5-second intervals, 3 precise measurements are made each day and ed worldwide to a list of users such as the NOAA Space Weather Prediction Center at and

23. "The current prediction for Sunspot Cycle 24 gives a smoothed sunspot
PREDICTIONS
"The current prediction for Sunspot
Cycle 24 gives a smoothed sunspot
number maximum of about 69 in the
late Summer of The smoothed
sunspot number reached 68.9 in
August 2013 so the official
maximum will be at least this high.
The smoothed sunspot number has
been rising again towards this second
peak over the last five months and
has now surpassed the level of the
first peak (66.9 in February 2012). Many cycles are double peaked but this is the first in which the second peak in sunspot number was larger than the first. We are currently over five years into Cycle 24. The current predicted and observed size makes this the smallest sunspot cycle since Cycle 14 which had a maximum of 64.2 in February of 1906."[1]
Most cycles are double peaked. This data is from 2013

24. Solar Cycle 25 Preliminary Forecast
published: Tuesday, June 11, :03 UTC
The NOAA/NASA co-chaired international panel to forecast Solar Cycle 25 released a preliminary forecast for Solar Cycle 25 on April 5, The consensus: Cycle 25 will be similar in size to cycle 24.  
It is expected that sunspot maximum will occur no earlier than the year 2023 and no later than 2026 with a minimum peak sunspot number of 95 and a maximum of 130.  In addition, the panel expects the end of Cycle 24 and start of Cycle 25 to occur no earlier than July, 2019, and no later than September, 2020.  The panel hopes to release a final, detailed forecast for Cycle 25 by the end of 2019.  Please read the official NOAA press release describing the international panel's forecast at
Peak predicted to occur between 2023 and Peak number of spots to be between 95 and 130.

25. NOAA/NASA Solar Cycle 25 Preliminary Forecast
published: Tuesday, June 11, :03 UTC

27. A second prediction. Previous results Successfully predicted cycle 24
NOAA & NASA Solar Cycle 25 Forecasts – A Comparison based on Combined sunspot number and observed solar magnetic fields. Research by I. Kitiashvili NASA AMES Research Center, CA.
Previous results
Successfully predicted cycle 24
Uses SDO and SOHO satellite data.
Uses a model which is highly complex using
observational data.
Predictions
Extended solar minimum.
Maximum in
Peak sunspot number of 50 with estimated error of 15-30%

28. Data collected from SOHO (Solar and Heliospheric Observatory), SDO (Solar Dynamic Observatory) and NSO (Solar, National Solar Observatory) Data is based on observations over the last 4 solar cycles. Magnetic data from NSO since 1976.

29. A 3rd Prediction by David Birch (independent solar researcher).
This prediction is consistent with a new paper by Valentina Zharkova
confirming the next Grand Solar Minimum titled, Oscillations of the
baseline of solar magnetic field and solar irradiance on a millennial
timescale published in Nature. 25 26
Note that the period from about 1790 to 1830 may be similar to cycles 22, 23, 24 & 25. Birch predicts a sunspot number peak of 50 for cycle 25. Zharkova predicts a Grand Solar Minimum similar to the Maunder Minimum which starts in 2020 and continues to 2055 and will again arrive in Her team's calculations match up with the timelines of the Maunder Minimum (1645–1715), Wolf minimum (1300–1350), Oort minimum (1000–1050), Homer minimum (800–900 BC); also the Medieval Warm Period (900–1200), the Roman Warm Period (400–150 BC) and so on with great accuracy.

30. Note that the period from about 1790 to 1830 may be similar to cycles 22, 23, 24 & 25. Birch predicts a sunspot number peak of 50 for cycle 25. Zharkova predicts a Grand Solar Minimum similar to the Maunder Minimum which starts in 2020 and continues to 2055 and will again arrive in Her team's calculations match up with the timelines of the Maunder Minimum (1645–1715), Wolf minimum (1300–1350), Oort minimum (1000–1050), Homer minimum (800–900 BC); also the Medieval Warm Period (900–1200), the Roman Warm Period (400–150 BC) and so on with great accuracy. So he says! TBD.