Stars/Sun/Solar cycles

File:Jupiter sized sunspot AR 2192.jpg

AR 2192 is a sprawling solar active region comparable in size to the diameter of Jupiter. Credit: Randall Shivak and Alan Friedman (Averted Imagination).

The surface of the Sun (surface of the photosphere) undergoes a cycle of sunspot activity with a period around 11 years. The exact cause, or even approximate cause, of the sunspot, or solar cycle, is unknown.

Colors

Main resources: Radiation astronomy/Colors and Color astronomy

This is a montage of solar activity during a sunspot cycle. Credit: David Chenette, Joseph B. Gurman, Loren W. Acton.

At right is a montage of ten years' worth of Yohkoh SXT images, demonstrating the variation in solar activity during a sunspot cycle, from after August 30, 1991, to September 6, 2001.

Spörer's law

"For the greater part of the sun-spot period there is practically but one zone of spots in each hemisphere. The departure from this condition of things near or at the time of minimum, when the spots of the dying cycle are approaching the equator, and the forerunners of the new cycle are beginning to appear in high latitudes, is the only case in which the solar spots are distinctly separated into more than a single zone in each hemisphere." "Spöerer's law ... involves that in a minimum year the zone about 15° should be entirely barren".

"First of all there were only fifteen groups seen during the entire year [1901], north and south put together. Of these, seven were in the north, and the mean latitude for the north was 8.6°, exactly the latitude of one spot of the seven, and this very naturally, seeing that it was by far the greatest group of the year, the celebrated "eclipse group."" Bold added. "Greatest group" and "eclipse group" are both relative synonyms for "dominant group".

"[T]he spot-groups have been carefully examined for cases of return, and where it appeared clear that the same group has returned a second time or more frequently, without any temporary disappearance or subsidence, such a long-continued group has been treated as an entity throughout." Bold added. "It has been forgotten that, whatever the cause which produces this variation of rotation rate with latitude, the causes producing difference of rate within any given latitude are more effective still."

"[T]here is a slight retardation of the rotation period from the first cycle to the second, shown by both northern and southern hemispheres."

Theoretical solar cycles

The diagram shows positional conjunctions for the planets. Credit: Wmheric.

"The principal objective of this study is to invent a simple, quantitative, closed kinematical model of the solar cycle which is based as far as possible either on well-accepted physical effects or on observed facts (whether fully understood or not), in the hope that such a model might single out the most important factors for detailed study, and might suggest further directions for investigation."

"[T]he model describes ... the time variation of average sunspot latitudes (Spoerer's law) and the width of the eruption zone (Maunder's butterfly diagram)".

The conjunctions of Venus and Jupiter can occur at about opposite sides of Jupiter's orbital period of ~ 11 yrs around the Sun.

Flip-flop cycles

"Another activity cycle is the so called flip-flop cycle, which implies that the activity on either hemisphere shifts from one side to the other. The same phenomena can be seen on the Sun, with periods of 3.8 and 3.65 years for the northern and southern hemispheres. Flip-flop phenomena are observed for both binary [RS Canum Venaticorum variable] RS CVn stars and single stars although the extent of the cycles are different between binary and singular stars."

Plasma objects

Main resources: Plasmas/Plasma objects and Plasma objects

Def. "[t]he luminous plasma atmosphere of the Sun or other star, extending millions of kilometres into space, most easily seen during a total solar eclipse", from Wiktionary corona, is called a corona, or stellar corona.

From the learning resource theoretical astronomy is this regarding the early historical theory of the solar corona:

The solar corona is photographed between 1901-2. Credit: Popular Science Monthly Volume 60.

"Beginning with the daguerreotype of the corona of 1851, the Reverend Lecturer had thrown on the screen pictures illustrating the form of the corona in different years. The drawings of those of 1867, 1878, and 1900 all showed long equatorial extensions with openings at the solar poles filled with beautiful rays." "The intermediate years, as, for example, 1883, 1886, and 1896 showed the four groups of synclinals which mainly constitute the corona gradually descending towards the equator of the sun, with a corresponding opening of the polar regions."

"Some of the theories of the solar corona were then illustrated and discussed."

1. "The corona is not of the nature of an atmosphere round the sun, for the pressure at the sun's limb would be enormous, while the thinness of the chromospheric lines show that it is not."
2. "comets, such as that of 1843, have approached the sun with enormous velocities within the region of the prominences without suffering disruption or retardation."
3. "If not an atmosphere of particles of gas, still less is it an atmosphere of solid stones or meteorites."
4. "Meteor streams do circle round the sun, but there is no reason why the positions of the orbits, or the intrinsic brightness of such streams should vary with the sun-spot period."
5. "the appearance of the corona does not seem to be such as the projection of meteor streams upon the celestial vault would give."
6. "Prof. Schaeberle has proposed a mechanical origin of the solar corona, due to the forces of ejection of particles from the solar limb, as evidenced by the prominences, and the force of gravity under the particular conditions of the solar rotation and the inclination of its axis to the earth's orbit."
7. "The electrical theory of the corona does not negative the mechanical theory, but supplements it. In addition to the forces of gravity and ejection, it takes account of the repulsive force which the sun exerts on matter which has the same electrical sign as itself, and which has been ejected from it."
8. "it would seem that the solar corona is of the nature of an electrical aurora round the sun."
9. "the coronoidal discharges in poor vacua obtained by Prof. Pupin about an insulated metal ball are exceedingly like the rays and streamers of the solar corona."

"The Sun's hot corona continuously expands in space creating the solar wind, a stream of charged particles that extends to the heliopause at roughly 100 astronomical units. The bubble in the interstellar medium formed by the solar wind, the heliosphere, is the largest continuous structure in the Solar System."

"[T]he sun's corona is constantly being lost to space, creating what is essentially a very thin atmosphere throughout the Solar System. The movement of mass ejected from the Sun is known as the solar wind. Inconsistencies in this wind and larger events on the surface of the star, such as coronal mass ejections, form a system that has features analogous to conventional weather systems (such as pressure and wind) and is generally known as space weather. Coronal mass ejections have been tracked as far out in the solar system as Saturn. The activity of this system can affect planetary atmospheres and occasionally surfaces. The interaction of the solar wind with the terrestrial atmosphere can produce spectacular aurorae, and can play havoc with electrically sensitive systems such as electricity grids and radio signals."

Space weather

Main resources: Astronomy/Skys/Weather/Space and Space weather

The butterfly diagam shows paired sunspot pattern. The graph is of sunspot Wolf number versus time. Credit: .

"The solar cycle has a great influence on space weather, and a significant influence on the Earth's climate since the Sun's luminosity has a direct relationship with magnetic activity. Solar activity minima tend to be correlated with colder temperatures, and longer than average solar cycles tend to be correlated with hotter temperatures. In the 17th century, the solar cycle appeared to have stopped entirely for several decades; few sunspots were observed during this period. During this era, known as the Maunder minimum or Little Ice Age, Europe experienced unusually cold temperatures. Earlier extended minima have been discovered through analysis of tree rings and appear to have coincided with lower-than-average global temperatures."

"MOST current literature on solar activity assumes that the planets do not affect it, and that conditions internal to the Sun are primarily responsible for the solar cycle. Bigg¹, however, has shown that the period of Mercury's orbit appears in the sunspot data, and that the influence of Mercury depends on the phases of Venus, Earth, and Jupiter."

"It is shown that starting with the alignment of Venus with Jupiter at perihelion position, these two planets will perfectly align at Jupiter's perihelion after every 23.7 years".

"The tidal forces hypothesis for solar cycles has been proposed by Wood (1972) and others. Table 2 below shows the relative tidal forces of the planets on the sun. Jupiter, Venus, Earth and Mercury are called the "tidal planets" because they are the most significant. According to Wood, the especially good alignments of J-V-E with the sun which occur about every 11 years are the cause of the sunspot cycle. He has shown that the sunspot cycle is synchronous with the alignments, and J. Schove's data for 1500 year of sunspot maxima supports the 11.07 year J-V-E period average."

"Both the 11.86 year Jupiter tropical period (time between perihelion's or closest approaches to the sun and the 9.93 year J-S alignment periods are found in sunspot spectral analysis. Unfortunately direct calculations of the tidal forces of all planets does not support the occurrence of the dominant 11.07 year cycle. Instead, the 11.86 year period of Jupiter's perihelion dominates the results. This has caused problems for several researchers in this field."

"[B]y assuming a harmonic variation having a period of 11.13 years ... the phases of such a variation [in polar diameter minus equatorial diameter of the Sun] coincide to within one-fifth of a year with the phases of the sun-spot fluctuations; that, at times corresponding to minimum of sun-spottedness, the polar diameter is relatively larger; that, at times of maximum sun-spottedness, the equatorial diameter is relatively larger. The amplitude of the variation is extremely small, but its reality would seem to be established. [This] at least renders the existence of such periodic fluctuations in the shape of the sun more probable than their non-existence."

"Solar oblateness, the difference between the equatorial and polar diameters, reflects certain fundamental properties of the Sun. ... the oblateness reflects properties of the Sun's interior, ... [There is] a time varying, excess equatorial brightness [producing] a difference between the equatorial and polar limb darkening functions ... at times when the excess brightness is reduced, the intrinsic visual oblateness can be obtained from the observations without detailed knowledge of the excess brightness. A period of reduced excess brightness occurred in 1973 September." The period of reduced excess equatorial brightness occurred between solar cycle maximum around 1970 and minimum around 1975. Considering excess equatorial brightness and seeking to perform measurements at opportunities of reduced excess equatorial brightness has the effect of reducing solar oblateness from some 86.6 ± 6.6 milli-arcsec to 18.4 ± 12.5 milli-arcsec.

"The Babcock Model describes a mechanism which can explain magnetic and sunspot patterns observed on the Sun."

1. "The start of the 22-year cycle begins with a well-established dipole field component aligned along the solar rotational axis. The field lines tend to be held by the highly conductive solar plasma of the solar surface."
2. "The solar surface plasma rotation rate is different at different latitudes, and the rotation rate is 20 percent faster at the equator than at the poles (one rotation every 27 days). Consequently, the magnetic field lines are wrapped by 20 percent every 27 days."
3. "After many rotations, the field lines become highly twisted and bundled, increasing their intensity, and the resulting buoyancy lifts the bundle to the solar surface, forming a bipolar field that appears as two spots, being kinks in the field lines."
4. "The sunspots result from the strong local magnetic fields in the solar surface that exclude the light-emitting solar plasma and appear as darkened spots on the solar surface."
5. "The leading spot of the bipolar field has the same polarity as the solar hemisphere, and the trailing spot is of opposite polarity. The leading spot of the bipolar field tends to migrate towards the equator, while the trailing spot of opposite polarity migrates towards the solar pole of the respective hemisphere with a resultant reduction of the solar dipole moment. This process of sunspot formation and migration continues until the solar dipole field reverses (after about 11 years)."
6. "The solar dipole field, through similar processes, reverses again at the end of the 22-year cycle."
7. "The magnetic field of the spot at the equator sometimes weakens, allowing an influx of coronal plasma that increases the internal pressure and forms a magnetic bubble which may burst and produce an ejection of coronal mass, leaving a coronal hole with open field lines. Such a coronal mass ejections are a source of the high-speed solar wind."
8. "The fluctuations in the bundled fields convert magnetic field energy into plasma heating, producing emission of electromagnetic radiation as intense ultraviolet (UV) and X-rays."

Planetary astronomy

Main resources: Planets/Astronomy and Planetary astronomy

ISES Solar Cycle 24 shows Sunspot Number Progression. Credit: NOAA/Space Weather Prediction Center.

File:Jupitervenus.ngsversion.eccb2228e6dd253fdd5d1027219277cf.adapt.676.1.jpg

Shown here, the planets Jupiter and Venus hover over Washington in 2008. Credit: Jason Reed, Reuters.

File:CI2t4NFWEAAFkku.jpg

Check out this amazing picture of the Venus-Jupiter conjunction. Credit: Norman Marigza.

Conjunction of the Moon, Venus (left) and Jupiter is seen from Sao Paulo, Brazil, on December 1st, 2008. Credit: Cláudio Pires e A. de Souza.

Yesterday, in the morning of 1 May 2011, about an hour before sunrise, five of our Solar System’s eight planets and the Moon could be seen from Paranal. Credit: Gerhard Hüdepohl/ESO.

The image on the right shows the sunspot minimum around January 2009 and the most recent sunspot maximum around March 2015.

On the left is an image of the Moon, Venus and Jupiter, from left to right, at about the time of the solar cycle minimum for cycle 24. The second image on the left has a more specific date of December 1, 2008. The third image down on the left shows a conjunction of Mars and Jupiter on May 1, 2011, about half way between solar minimum and solar maximum for cycle 24.

The image down on the right shows another conjunction of Venus and Jupiter. This one is at about the time, or just after, the solar maximum for cycle 24.

Earth polar ice caps

"The records show that prior to 2005, while sea ice extent in the Arctic varied for the month of January, it was always greater than 14.25 million sq. km. Since 2005, it has always been below that figure. There has been a 3.2 percent decline in winter Arctic ice for the decade."

"The February North American snow cover extent was 16.68 million square km (6.44 million square miles), 440,000 square km (170,000 square miles) below average. This was the 13th smallest February SCE on record, and the smallest since 2005."

"According to the National Snow and Ice Data Center (NSIDC), the Northern Hemisphere (Arctic) sea ice extent — which is measured from passive microwave instruments onboard NOAA satellites — averaged for February 2016 was 14.22 million square km (5.49 million square miles), 1.16 million square km (450,000 square km), or 7.54 percent, below the 1981-2010 average. This was the smallest February sea ice extent on record for the Arctic, 180,000 square km (70,000 square miles) smaller than the previous record in 2005."

"All 10 of the smallest sea ice extents on record have occurred since 2005. In the nearly four decades of satellite monitoring, sea ice has disappeared at a clip of 13.4 percent per decade. This year’s cracked ice also continues a troubling trend of disappearing old ice. Though some of that ice will refreeze together this winter, some has disappeared for good and new ice will be left to fill in the gaps."

For January, the "month’s average now sits at negative 3.2 percent every decade based on data collected since 1979. It also continues a trend of a less than 5.5-million-square-mile extent reported in each consecutive January since 2005."

"Despite what appears to be a consistent downward tendency in sea ice extent, a recent study published in Geophysical Research Letters suggests that the rate of Arctic ice loss may actually be slowing, at least in the Atlantic. Even though the January trend is on a negative trajectory, a tendency for more ice overall has been observed since 2005."

“There is little doubt that we will see a decline in Arctic sea ice cover in this century in response to anthropogenic warming, However, internal climate variations and other external forcings could generate considerable spread in Arctic sea ice trends on decadal timescales.”

"Edinburgh and Day (2016) used historical monitoring records to conclude that “the [Antarctic sea ice] levels in the early 1900s were in fact similar to today“."

"Arctic sea ice has also remained essentially unchanged since the 1930s and 1940s too, and is overall still quite high relative to recent centennial- and millennial-scale historical periods. Even for the last few decades, the trends are not unusual."

The "IPCC referenced NOAA satellite data that extended back to 1972, not 1979, in the first UN report (1990). It showed that there had been a slight increasing trend in sea ice for 1972-1990 due to the low extent recorded during the early 1970s, and the very high extent in the late 1970s, when the current satellite datasets begin. Now, the IPCC (and NOAA, NSIDC) discard the 1972-1978 data from the sea ice record, instead using 1979 as the starting point, or the year with the highest sea ice extent since the early 20th century. This way, the decline in sea ice extent to the present can be steepened considerably in modern graphics."

"Between 1990 and 2006, Arctic sea ice declined rapidly. Since 2006, however, the sea ice decline has undergone a pause, as shown in NSIDC data (using WoodForTrees.org interactive graphs):"

"For the early 20th century, there was a dramatic decline in Arctic sea ice between the 1920s and 1940s that was concomitant with the as-warm-as-present Arctic surface temperatures (top graph). After this abrupt warming trend ended, the Arctic cooled for several decades and a subsequent increase in sea ice occurred through the late 1970s. Hoffert and Flanney (1985) furnish a graph with recorded sea ice trends for 1920-1975."

"Solar forcing as an important trigger for West Greenland sea-ice variability over the last millennium … Here, we use diatom assemblages from a marine sediment core collected from the West Greenland shelf to reconstruct changes in sea-ice cover over the last millennium. The proxy-based reconstruction demonstrates a generally strong link between changes in sea-ice cover and solar variability during the last millennium. Weaker (or stronger) solar forcing may result in the increase (or decrease) in sea-ice cover west of Greenland. In addition, model simulations show that variations in solar activity not only affect local sea-ice formation, but also control the sea-ice transport from the Arctic Ocean through a sea-ice–ocean–atmosphere feedback mechanism."

"The Arctic sea ice experienced a drastic reduction that was phased with warming temperatures 1923 to 1940. This reduction was followed by a sharp cooling and sea ice recovery. This permits us to also conclude that very likely the Arctic sea ice extent also has a quasi-60 years’ oscillation. The recognition of a quasi-60 year’s oscillation in the sea ice extent of the Arctic similar to the oscillation of the temperatures and the other climate indices may permit us to separate the natural from the anthropogenic forcing of the Arctic sea ice. The heliosphere and the Earth’s magnetosphere may have much stronger influence on the climate patterns on Earth including the Arctic sea ices than has been thought."

The "approximately 80 year variability of the Koch [sea ice] index [has been compared] to the similar periodicity found in the solar cycle length, which is a measure of solar activity. A close correlation (R=0.67) of high significance (0.5 % probability of a chance occurrence) is found between the two patterns, suggesting a link from solar activity to the Arctic Ocean climate. … The 'low frequency oscillation' that dominated the ice export through the Fram Strait as well as the extension of the sea-ice in the Greenland Sea and Davis Strait in the twentieth century may therefore be regarded as part of a pattern that has existed through at least four centuries. The pattern is a natural feature, related to varying solar activity."

"Updated data from NASA satellite instruments reveal the Earth’s polar ice caps have not receded at all since the satellite instruments began measuring the ice caps in 1979. Since the end of 2012, moreover, total polar ice extent has largely remained above the post-1979 average. The updated data contradict one of the most frequently asserted global warming claims – that global warming is causing the polar ice caps to recede."

"Beginning in 2005, however, polar ice modestly receded for several years. By 2012, polar sea ice had receded by approximately 10 percent from 1979 measurements. (Total polar ice area – factoring in both sea and land ice – had receded by much less than 10 percent, but alarmists focused on the sea ice loss as “proof” of a global warming crisis.)"

"In late 2012, however, polar ice dramatically rebounded and quickly surpassed the post-1979 average. Ever since, the polar ice caps have been at a greater average extent than the post-1979 mean."

Starspots

Main resources: Stars/Starspots and Starspots

"Starspots are equivalent to sunspots but located on other stars. Spots the size of sunspots are very hard to detect since they are too small to cause fluctuations in brightness. Observed starspots are in general much larger than those on the Sun, up to about 30 % of the stellar surface may be covered, corresponding to sizes 100 times greater than those on the Sun."

"The distribution of starspots across the stellar surface varies analogous to the solar case, but differs for different types of stars, e.g., depending on whether the star is a binary or not. The same type of activity cycles that are found for the Sun can be seen for other stars, corresponding to the solar (2 times) 11-year cycle. Some stars have longer cycles, possibly analogous to the Maunder minima for the Sun."

Pennsylvanian

Main resources: History/Pennsylvanian and Pennsylvanian

The Pennsylvanian lasted from 318.1 ± 1.3 to 299.0 ± 0.8 Mb2k.

"Studies of stratigraphic data have suggested that the solar cycles have been active for hundreds of millions of years, if not longer; measuring varves in precambrian sedimentary rock has revealed repeating peaks in layer thickness, with a pattern repeating approximately every eleven years. It is possible that the early atmosphere on Earth was more sensitive to changes in solar radiation than today, so that greater glacial melting (and thicker sediment deposits) could have occurred during years with greater sunspot activity. This would presume annual layering; however, alternate explanations (diurnal) have also been proposed."

Prehistory

Main resources: History/Prehistory and Prehistory

The prehistory period dates from around 7 x 10⁶ b2k to about 7,000 b2k.

Paleolithic

Main resources: History/Paleolithic and Paleolithic history

The paleolithic period dates from around 2.6 x 10⁶ b2k to the end of the Pleistocene around 12,000 b2k.

Mesolithic

Main resources: History/Mesolithic and Mesolithic history

The mesolithic period dates from around 13,000 to 8,500 b2k.

"Analysis of tree rings has revealed a detailed picture of past solar cycles: Dendrochronologically dated radiocarbon concentrations have allowed for a reconstruction of sunspot activity dating back 11,400 years, far beyond the four centuries of available, reliable records from direct solar observation."

Ancient history

Main resources: History/Ancient and Ancient history

The ancient history period dates from around 8,000 to 3,000 b2k.

Early history

Main resources: History/Early and Early history

The early history period dates from around 3,000 to 2,000 b2k.

"The earliest surviving record of sunspot observation dates from 364 BC, based on comments by Chinese astronomer Gan De in a star catalogue. By 28 BC, Chinese astronomers were regularly recording sunspot observations in official imperial records."

Classical history

Main resources: History/Classics and Classical history

The classical history period dates from around 2,000 to 1,000 b2k.

Recent history

Main resources: History/Recent and Recent history

Measurements of solar cycle variation are included for the last 30 years. Credit: Robert A. Rohde.

History of the number of observed sunspots during the last 250 years shows the ~11-year solar cycle. Credit: Leland McInnes.

This figure summarizes sunspot number observations. Credit: Robert A. Rohde.

Changes in ¹⁴C concentration in the Earth's atmosphere serve as a long term proxy of solar activity. Note the present day is on the right-hand side. Credit: USGS.

The recent history period dates from around 1,000 b2k to present.

"Sunspots are temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. They are caused by intense magnetic activity, which inhibits convection by an effect comparable to the eddy current brake, forming areas of reduced surface temperature. Like magnets, they also have two poles. Although they are at temperatures of roughly 3,000–4,500 K (2,727–4,227 °C), the contrast with the surrounding material at about 5,780 K leaves them clearly visible as dark spots, as the luminous intensity of a heated black body (closely approximated by the photosphere) is a function of temperature to the fourth power. If the sunspot were isolated from the surrounding photosphere it would be brighter than an electric arc. Sunspots expand and contract as they move across the surface of the Sun and can be as large as 80,000 kilometers (49,710 mi) in diameter, making the larger ones visible from Earth without the aid of a telescope. They may also travel at relative speeds ("proper motions") of a few hundred m/s when they first emerge onto the solar photosphere."

"For the greater part of the sun-spot period there is practically but one zone of spots in each hemisphere. The departure from this condition of things near or at the time of minimum, when the spots of the dying cycle are approaching the equator, and the forerunners of the new cycle are beginning to appear in high latitudes, is the only case in which the solar spots are distinctly separated into more than a single zone in each hemisphere." "Spöerer's law ... involves that in a minimum year the zone about 15° should be entirely barren".

"First of all there were only fifteen groups seen during the entire year [1901], north and south put together. Of these, seven were in the north, and the mean latitude for the north was 8.6°, exactly the latitude of one spot of the seven, and this very naturally, seeing that it was by far the greatest group of the year, the celebrated "eclipse group."" Bold added. "Greatest group" and "eclipse group" are both relative synonyms for "dominant group".

"[T]he spot-groups have been carefully examined for cases of return, and where it appeared clear that the same group has returned a second time or more frequently, without any temporary disappearance or subsidence, such a long-continued group has been treated as an entity throughout." Bold added. "It has been forgotten that, whatever the cause which produces this variation of rotation rate with latitude, the causes producing difference of rate within any given latitude are more effective still."

"[T]here is a slight retardation of the rotation period from the first cycle to the second, shown by both northern and southern hemispheres."

"The number of sunspots visible on the Sun is not constant, but varies over an 11-year cycle known as the solar cycle. At a typical solar minimum, few sunspots are visible, and occasionally none at all can be seen. Those that do appear are at high solar latitudes. As the sunspot cycle progresses, the number of sunspots increases and they move closer to the equator of the Sun, a phenomenon described by Spörer's law. Sunspots usually exist as pairs with opposite magnetic polarity. The magnetic polarity of the leading sunspot alternates every solar cycle, so that it will be a north magnetic pole in one solar cycle and a south magnetic pole in the next.

Numbers

Main resource: Numbers

This graph shows Wolf numbers since 1750. Credit: NASA.

"[T]he longest data set, the Wolf sunspot number (R), is determined from visible wavelength observations of the solar surface."

"The Wolf number (also known as the International sunspot number, relative sunspot number, or Zürich number) is a quantity that measures the number of sunspots and groups of sunspots present on the surface of the sun."

"This number has been collected and tabulated by researchers for over 150 years."

"The relative sunspot number $R$ is computed using the formula (collected as a daily index of sunspot activity):

$R=k(10g+s)\,$

where

• $s$ is the number of individual spots,
• $g$ is the number of sunspot groups, and
• $k$ is a factor that varies with location and instrumentation (also known as the observatory factor or the personal reduction coefficient $K$)."

Hypotheses

Main resource: Hypotheses

1. Some configuration of Venus and Jupiter precisely corresponds to the major solar cycle period.

See also: Control groups, Proof of concept, and Proof of technology

See also

• Stars/Sun

External links

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