![Sunspot Numbers](https://upload.wikimedia.org/wikipedia/commons/2/28/Sunspot_Numbers.png)
The solar cycle, also known as the solar magnetic activity cycle, sunspot cycle, or Schwabe cycle, is a nearly periodic 11-year change in the
Sun's activity measured in terms of variations in the number of observed
sunspot
Sunspots are phenomena on the Sun's photosphere that appear as temporary spots that are darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic flux that inhibit convection. Sun ...
s on the
Sun's surface
The photosphere is a star's outer shell from which light is radiated.
The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it ...
. Over the period of a solar cycle, levels of
solar radiation
Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument.
Solar irradiance is measured in watts per square metre (W/m ...
and ejection of solar material, the number and size of
sunspot
Sunspots are phenomena on the Sun's photosphere that appear as temporary spots that are darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic flux that inhibit convection. Sun ...
s,
solar flares, and
coronal loops all exhibit a synchronized fluctuation from a
period of minimum activity to a
period of a maximum activity back to a period of minimum activity.
The magnetic field of the Sun flips during each solar cycle, with the flip occurring when the solar cycle is near its maximum. After two solar cycles, the Sun's magnetic field returns to its original state, completing what is known as a Hale cycle.
This cycle has been observed for centuries by changes in the Sun's appearance and by terrestrial phenomena such as
aurora but was not clearly identified until 1843. Solar activity, driven by both the solar cycle and transient aperiodic processes, governs the environment of
interplanetary space
Interplanetary may refer to:
*Interplanetary space, the space between the planets of the Solar System
*Interplanetary spaceflight, travel between planets
*The interplanetary medium, the material that exists in interplanetary space
*The InterPlanet ...
by creating space weather and impacting space- and ground-based technologies as well as the Earth's atmosphere and also possibly climate fluctuations on scales of centuries and longer.
Understanding and predicting the solar cycle remains one of the grand challenges in astrophysics with major ramifications for space science and the understanding of
magnetohydrodynamic phenomena elsewhere in the universe.
Definition
Solar cycles have an average duration of about 11 years.
Solar maximum and
solar minimum refer to periods of maximum and minimum sunspot counts. Cycles span from one minimum to the next.
Observational history
The idea of a cyclical solar cycle was first hypothesized by
Christian Horrebow based on his regular observations of
sunspot
Sunspots are phenomena on the Sun's photosphere that appear as temporary spots that are darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic flux that inhibit convection. Sun ...
made between 1761 and 1776 from the
Rundetaarn
The Round Tower (Danish: Rundetårn) is a 17th-century tower in Copenhagen, Denmark, one of the many architectural projects of Christian IV of Denmark. Built as an astronomical observatory, it is noted for its equestrian staircase, a 7.5-turn he ...
observatory in
Copenhagen
Copenhagen ( or .; da, København ) is the capital and most populous city of Denmark, with a proper population of around 815.000 in the last quarter of 2022; and some 1.370,000 in the urban area; and the wider Copenhagen metropolitan ar ...
,
Denmark
)
, song = ( en, "King Christian stood by the lofty mast")
, song_type = National and royal anthem
, image_map = EU-Denmark.svg
, map_caption =
, subdivision_type = Sovereign state
, subdivision_name = Danish Realm, Kingdom of Denmark
...
. In 1775, Horrebow noted how "it appears that after the course of a certain number of years, the appearance of the Sun repeats itself with respect to the number and size of the spots". The solar cycle however would not be clearly identified until 1843 when
Samuel Heinrich Schwabe
Samuel Heinrich Schwabe (25 October 1789 – 11 April 1875) a German astronomer remembered for his work on sunspots.
Schwabe was born at Dessau. At first an apothecary, he turned his attention to astronomy, and in 1826 commenced his observatio ...
noticed a periodic variation in the average number of sunspots after 17 years of solar observations.
[ From page 235: ''"Vergleicht man nun die Zahl der Gruppen und der flecken-freien Tage mit einander, so findet man, dass die Sonnenflecken eine Periode von ungefähr 10 Jahren hatten … "'' (If one compares the number of groups ]f sunspots
F, or f, is the sixth letter in the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''ef'' (pronounced ), and the plural is ''efs''.
Hist ...
and the sunspot-free days with one another, then one finds that the sunspots had a period of about 10 years … ) Schwabe continued to observe the sunspot cycle for another 23 years, until 1867. In 1852,
Rudolf Wolf
Johann Rudolf Wolf (7 July 1816 – 6 December 1893) was a Swiss astronomer and mathematician best known for his research on sunspots.
Wolf was born in Fällanden, near Zurich. He studied at the universities of Zurich, Vienna, and Berlin. Encke ...
designated the first numbered solar cycle to have started in February 1755 based on Schwabe's and other observations. Wolf also created a standard sunspot number index, the
Wolf number
The Wolf number (also known as the 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.
History
Astronomers have been observing the Sun recordi ...
, which continues to be used today.
Between 1645 and 1715, very few sunspots were observed and recorded. This was first noted by
Gustav Spörer and was later named the
Maunder minimum after the wife-and-husband team
Annie S. D. Maunder
Annie Scott Dill Maunder (née Russell) (14 April 1868 – 15 September 1947) was an Irish-British astronomer, who recorded the first evidence of the movement of sunspot emergence from the poles toward the equator over the sun's 11-year cycle. ...
and
Edward Walter Maunder who extensively researched this peculiar interval.
In the second half of the nineteenth century
Richard Carrington and Spörer independently noted the phenomena of sunspots appearing at different heliographic latitudes at different parts of the cycle. (See
Spörer's law.)
Alfred Harrison Joy would later describe how the magnitude at which the sunspots are "tilted"—with the leading spot(s) closer to the equator than the trailing spot(s)―grows with the latitude of these regions. (See
Joy's law.)
The cycle's physical basis was elucidated by
George Ellery Hale
George Ellery Hale (June 29, 1868 – February 21, 1938) was an American solar astronomer, best known for his discovery of magnetic fields in sunspots, and as the leader or key figure in the planning or construction of several world-lea ...
and collaborators, who in 1908 showed that sunspots were strongly magnetized (the first detection of magnetic fields beyond the Earth). In 1919 they identified a number of patterns which would collectively become known as
Hale's law
In solar physics, Hale's law, also known as Hale's polarity law or the Hale–Nicholson law, describes the tendency for bipolar active regions within the same northern or southern hemisphere to have the same leading magnetic polarity with respect ...
:
* In the same heliographic hemisphere, bipolar
active regions tend to have the same leading polarity.
* In the opposite hemisphere, i.e., across the equator, these regions tend to have the opposite leading polarity.
* Leading polarities in both hemispheres flip from one sunspot cycle to the next.
Hale's observations revealed that the complete magnetic cycle—which would later be referred to as a Hale cycle—spans two solar cycles, or 22 years, before returning to its original state (including polarity). Because nearly all manifestations are insensitive to polarity, the 11-year solar cycle remains the focus of research; however, the two halves of the Hale cycle are typically not identical: the 11-year cycles usually alternate between higher and lower sums of Wolf's sunspot numbers (the
Gnevyshev-Ohl rule).
In 1961 the father-and-son team of
Harold
Harold may refer to:
People
* Harold (given name), including a list of persons and fictional characters with the name
* Harold (surname), surname in the English language
* András Arató, known in meme culture as "Hide the Pain Harold"
Arts a ...
and
Horace Babcock established that the solar cycle is a spatiotemporal magnetic process unfolding over the Sun as a whole. They observed that the solar surface is magnetized outside of sunspots, that this (weaker) magnetic field is to first order a
dipole, and that this dipole undergoes polarity reversals with the same period as the sunspot cycle. Horace's
Babcock Model
The Babcock Model describes a mechanism which can explain magnetic and sunspot patterns observed on the Sun.
History
The modern understanding of sunspots starts with George Ellery Hale, who linked magnetic fields and sunspots. Hale suggested t ...
described the Sun's oscillatory magnetic field as having a quasi-steady periodicity of 22 years.
It covered the oscillatory exchange of energy between
toroidal and poloidal solar magnetic field components.
Cycle history
![Sunspots 11000 years](https://upload.wikimedia.org/wikipedia/commons/2/27/Sunspots_11000_years.svg)
Sunspot numbers over the past 11,400 years have been reconstructed using
carbon-14
Carbon-14, C-14, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and coll ...
isotope ratios. The level of solar activity beginning in the 1940s is exceptional – the last period of similar magnitude occurred around 9,000 years ago (during the warm
Boreal period).
[, ] The Sun was at a similarly high level of magnetic activity for only ~10% of the past 11,400 years. Almost all earlier high-activity periods were shorter than the present episode.
Fossil records suggest that the solar cycle has been stable for at least the last 700 million years. For example, the cycle length during the
Early Permian 01 or '01 may refer to:
* The year 2001, or any year ending with 01
* The month of January
* 1 (number)
Music
* '01 (Richard Müller album), 01'' (Richard Müller album), 2001
* 01 (Son of Dave album), ''01'' (Son of Dave album), 2000
* 01 (Urban ...
is estimated to be 10.62 years
and similarly in the
Neoproterozoic.
![Carbon14 with activity labels](https://upload.wikimedia.org/wikipedia/commons/5/5c/Carbon14_with_activity_labels.svg)
Until 2009, it was thought that 28 cycles had spanned the 309 years between 1699 and 2008, giving an average length of 11.04 years, but research then showed that the longest of these (1784–1799) may actually have been two cycles. If so then the average length would be only around 10.7 years. Since observations began cycles as short as 9 years and as long as 14 years have been observed, and if the cycle of 1784–1799 is double then one of the two component cycles had to be less than 8 years in length. Significant amplitude variations also occur.
Several lists of proposed historical "grand minima" of solar activity exist.
Recent cycles
Cycle 25
Solar cycle 25 began in December 2019.
Several predictions have been made for solar cycle 25
[for example: ] based on different methods, ranging from very weak to strong magnitude. A physics-based prediction relying on the data-driven solar dynamo and solar surface flux transport models by Bhowmik and Nandy (2018) seems to have predicted the strength of the solar polar field at the current minima correctly and forecasts a weak but not insignificant solar cycle 25 similar to or slightly stronger than cycle 24. Notably, they rule out the possibility of the Sun falling into a Maunder-minimum-like (inactive) state over the next decade. A preliminary consensus by a solar cycle 25 Prediction Panel was made in early 2019. The Panel, which was organized by NOAA's
Space Weather Prediction Center (SWPC) and
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding t ...
, based on the published solar cycle 25 predictions, concluded that solar cycle 25 will be very similar to solar cycle 24. They anticipate that the solar cycle minimum before cycle 25 will be long and deep, just as the minimum that preceded cycle 24. They expect solar maximum to occur between 2023 and 2026 with a sunspot range of 95 to 130, given in terms of the revised sunspot number.
Cycle 24
Solar cycle 24 began on 4 January 2008, with minimal activity until early 2010. The cycle featured a "double-peaked"
solar maximum. The first peak reached 99 in 2011 and the second in early 2014 at 101. Cycle 24 ended in December 2019 after 11.0 years.
Cycle 23
Solar cycle 23 lasted 11.6 years, beginning in May 1996 and ending in January 2008. The maximum smoothed sunspot number (monthly number of sunspots averaged over a twelve-month period) observed during the solar cycle was 120.8 (March 2000), and the minimum was 1.7.
A total of 805 days had no sunspots during this cycle.
Phenomena
Because the solar cycle reflects magnetic activity, various magnetically driven solar phenomena follow the solar cycle, including sunspots, faculae/plage, network, and coronal mass ejections.
Sunspots
![ChroniclesofJohnofWorcester](https://upload.wikimedia.org/wikipedia/commons/3/3d/ChroniclesofJohnofWorcester.jpg)
The Sun's apparent surface, the photosphere, radiates more actively when there are more sunspots. Satellite monitoring of
solar luminosity revealed a direct relationship between the solar cycle and luminosity with a peak-to-peak amplitude of about 0.1%.
Luminosity decreases by as much as 0.3% on a 10-day timescale when large groups of sunspots rotate across the Earth's view and increase by as much as 0.05% for up to 6 months due to
faculae
A facula (plural: faculae ), Latin for "little torch", is literally a "bright spot". The term has several common technical uses. It is used in planetary nomenclature for naming certain surface features of planets and moons,. and is also a type of ...
associated with large sunspot groups.
The best information today comes from
SOHO
Soho is an area of the City of Westminster, part of the West End of London. Originally a fashionable district for the aristocracy, it has been one of the main entertainment districts in the capital since the 19th century.
The area was develop ...
(a cooperative project of the
European Space Agency
, owners =
, headquarters = Paris, Île-de-France, France
, coordinates =
, spaceport = Guiana Space Centre
, seal = File:ESA emblem seal.png
, seal_size = 130px
, image = Views in the Main Control Room (1205 ...
and
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding t ...
), such as the MDI
magnetogram
Magnetogram may refer to:
* Solar magnetogram
In solar observation, a magnetogram is a pictorial representation of the spatial variations in strength of the solar magnetic field.
Solar magnetograms are produced by solar magnetographs. Some magne ...
, where the solar "surface"
magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
can be seen.
As each cycle begins, sunspots appear at mid-latitudes, and then move closer and closer to the equator until a solar minimum is reached. This pattern is best visualized in the form of the so-called butterfly diagram. Images of the Sun are divided into latitudinal strips, and the monthly-averaged fractional surface of sunspots is calculated. This is plotted vertically as a color-coded bar, and the process is repeated month after month to produce this time-series diagram.
![Sunspot-bfly](https://upload.wikimedia.org/wikipedia/commons/e/e1/Sunspot-bfly.gif)
While magnetic field changes are concentrated at sunspots, the entire sun undergoes analogous changes, albeit of smaller magnitude.
![Synoptic-solmag](https://upload.wikimedia.org/wikipedia/commons/3/33/Synoptic-solmag.jpg)
]
Faculae and plage
Faculae are bright magnetic features on the photosphere. They extend into the chromosphere, where they are referred to as plage. The evolution of plage areas is typically tracked from solar observations in the Ca II K line (393.37 nm). The amount of facula and plage area varies in phase with the solar cycle, and they are more abundant than sunspots by approximately an order of magnitude.
They exhibit a non linear relation to sunspots. Plage regions area also associated with strong magnetic fields in the solar surface.
Solar flares and coronal mass ejections
The solar magnetic field structures the corona, giving it its characteristic shape visible at times of solar eclipses. Complex coronal magnetic field structures evolve in response to fluid motions at the solar surface, and emergence of
magnetic flux
In physics, specifically electromagnetism, the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface. It is usually denoted or . The SI unit of magnetic flux is the weber ( ...
produced by
dynamo action in the solar interior. For reasons not yet understood in detail, sometimes these structures lose stability, leading to
solar flares and
coronal mass ejections (CME). Flares consist of an abrupt emission of energy (primarily at
ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
and
X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
wavelengths), which may or may not be accompanied by a coronal mass ejection, which consists of injection of energetic particles (primarily ionized hydrogen) into interplanetary space. Flares and CME are caused by sudden localized release of magnetic energy, which drives emission of ultraviolet and X-ray radiation as well as energetic particles. These eruptive phenomena can have a significant impact on Earth's upper atmosphere and space environment, and are the primary drivers of what is now called
space weather.
The occurrence frequency of coronal mass ejections and flares is strongly modulated by the cycle. Flares of any given size are some 50 times more frequent at solar maximum than at minimum. Large coronal mass ejections occur on average a few times a day at solar maximum, down to one every few days at solar minimum. The size of these events themselves does not depend sensitively on the phase of the solar cycle. A case in point are the three large X-class flares that occurred in December 2006, very near solar minimum; an X9.0 flare on Dec 5 stands as one of the brightest on record.
Patterns
![SpaceEnvironmentOverview From 19830101](https://upload.wikimedia.org/wikipedia/commons/6/6b/SpaceEnvironmentOverview_From_19830101.jpg)
Along with the approximately 11-year sunspot cycle, a number of additional patterns and cycles have been hypothesized.
[David H. Hathaway]
"The Solar Cycle"
''Living Reviews in Solar Physics,'' March 2010, Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany. ISSN
1614-4961 (accessed 19 July 2015)
Waldmeier effect
The Waldmeier effect describes the observation that the maximum amplitudes of solar cycles are inversely proportional to the time between their solar minima and maxima. Therefore, cycles with larger maximum amplitudes tend to take less time to reach their maxima than cycles with smaller amplitudes. This effect was named after
Max Waldmeier
Max Waldmeier (18 April 1912 – 26 September 2000) was a Swiss astronomer, known for his research on sunspots. As director of the Zurich Observatory until 1980, Waldmeier insisted on counting sunspots by eye over automated methods, using a ...
who first described it.
Gnevyshev–Ohl rule
The Gnevyshev–Ohl rule describes the tendency for the sum of the
Wolf number
The Wolf number (also known as the 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.
History
Astronomers have been observing the Sun recordi ...
over an odd solar cycle to exceed that of the preceding even cycle.
Gleissberg cycle
The Gleissberg cycle describes an amplitude modulation of solar cycles with a period of about 70–100 years, or seven or eight solar cycles. It was named after Wolfgang Gleißberg.
Associated centennial variations in magnetic fields in the
corona and
heliosphere have been detected using
carbon-14
Carbon-14, C-14, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and coll ...
and
beryllium-10 cosmogenic isotopes stored in terrestrial reservoirs such as
ice sheets and
tree ring
Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmos ...
s and by using historic observations of
geomagnetic storm activity, which bridge the time gap between the end of the usable cosmogenic isotope data and the start of modern satellite data.
These variations have been successfully reproduced using models that employ magnetic flux continuity equations and observed sunspot numbers to quantify the emergence of magnetic flux from the top of the solar atmosphere and into the
heliosphere, showing that sunspot observations, geomagnetic activity and cosmogenic isotopes offer a convergent understanding of solar activity variations.
Suess cycle
The Suess cycle, or de Vries cycle, is a cycle present in radiocarbon proxies of solar activity with a period of about 210 years.
It was named after
Hans Eduard Suess
Hans Eduard Suess (December 16, 1909 – September 20, 1993) was an Austrian born American physical chemist and nuclear physicist. He was a grandson of the Austrian geologist Eduard Suess.
Career
Suess earned his Ph.D. in chemistry from the Un ...
and
Hessel de Vries
Hessel de Vries (November 15, 1916 in Annen – December 23, 1959 in Groningen), was a Dutch physicist and professor at the University of Groningen who furthered the detection methods and applications of radiocarbon dating to a variety of scie ...
.
Despite calculated radioisotope production rates being well correlated with the 400-year sunspot record, there is little evidence of the Suess cycle in the 400-year sunspot record by itself.
Other hypothesized cycles
![Carbon-14-10kyr-Hallstadtzeit Cycles](https://upload.wikimedia.org/wikipedia/commons/1/17/Carbon-14-10kyr-Hallstadtzeit_Cycles.png)
Periodicity of solar activity with periods longer than the solar cycle of about 11 (22) years has been proposed, including:
* The Hallstatt cycle (named after a cool and wet
period in Europe when glaciers advanced) is hypothesized to extend for approximately 2,400 years.
* In studies of
carbon-14
Carbon-14, C-14, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and coll ...
ratios, cycles of 105, 131, 232, 385, 504, 805 and 2,241 years have been proposed, possibly matching cycles derived from other sources. Damon and Sonett proposed carbon 14-based medium- and short-term variations of periods 208 and 88 years; as well as suggesting a 2300-year radiocarbon period that modulates the 208-year period.
[see table in ]
*
Brückner-Egeson-Lockyer cycle (30 to 40 year cycles)
Effects
Solar
Surface magnetism
Sunspot
Sunspots are phenomena on the Sun's photosphere that appear as temporary spots that are darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic flux that inhibit convection. Sun ...
s eventually decay, releasing magnetic flux in the photosphere. This flux is dispersed and churned by turbulent convection and solar large-scale flows. These transport mechanisms lead to the accumulation of magnetized decay products at high solar latitudes, eventually reversing the polarity of the polar fields (notice how the blue and yellow fields reverse in the Hathaway/NASA/MSFC graph above).
The dipolar component of the solar magnetic field reverses polarity around the time of solar maximum and reaches peak strength at the solar minimum.
Space
Spacecraft
CMEs (
coronal mass ejections) produce a radiation flux of high-energy
protons
A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...
, sometimes known as solar cosmic rays. These can cause radiation damage to electronics and
solar cell
A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon. s in
satellites
A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotop ...
. Solar proton events also can cause
single-event upset (SEU) events on electronics; at the same, the reduced flux of galactic cosmic radiation during solar maximum decreases the high-energy component of particle flux.
CME radiation is dangerous to
astronaut
An astronaut (from the Ancient Greek (), meaning 'star', and (), meaning 'sailor') is a person trained, equipped, and deployed by a human spaceflight program to serve as a commander or crew member aboard a spacecraft. Although generally r ...
s on a space mission who are outside the shielding produced by the
Earth's magnetic field
Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magnetic f ...
. Future mission designs (''e.g.'', for a
Mars Mission
Mars mission may refer to:
Space missions
* Exploration of Mars, or any mission to assist in this endeavour
** List of missions to Mars
*** List of Mars orbiters
**** Mars Orbiter Mission, India's first interplanetary mission
*** Mars rover missio ...
) therefore incorporate a radiation-shielded "storm shelter" for astronauts to retreat to during such an event.
Gleißberg developed a CME forecasting method that relies on consecutive cycles.
The increased irradiance during solar maximum expands the envelope of the Earth's atmosphere, causing low-orbiting
space debris
Space debris (also known as space junk, space pollution, space waste, space trash, or space garbage) are defunct human-made objects in space—principally in Earth orbit—which no longer serve a useful function. These include derelict spacecr ...
to re-enter more quickly.
Galactic cosmic ray flux
The outward expansion of solar ejecta into interplanetary space provides overdensities of plasma that are efficient at scattering high-energy
cosmic rays
Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
entering the solar system from elsewhere in the galaxy. The frequency of solar eruptive events is modulated by the cycle, changing the degree of cosmic ray scattering in the outer solar system accordingly. As a consequence, the cosmic ray flux in the inner Solar System is anticorrelated with the overall level of solar activity. This anticorrelation is clearly detected in cosmic ray flux measurements at the Earth's surface.
Some high-energy cosmic rays entering Earth's atmosphere collide hard enough with molecular atmospheric constituents that they occasionally cause nuclear
spallation reactions. Fission products include radionuclides such as
14C and
10Be that settle on the Earth's surface. Their concentration can be measured in tree trunks or ice cores, allowing a reconstruction of solar activity levels into the distant past. Such reconstructions indicate that the overall level of solar activity since the middle of the twentieth century stands amongst the highest of the past 10,000 years, and that epochs of suppressed activity, of varying durations have occurred repeatedly over that time span.
Atmospheric
Solar irradiance
The total solar irradiance (TSI) is the amount of solar radiative energy incident on the Earth's upper atmosphere. TSI variations were undetectable until satellite observations began in late 1978. A series of
radiometers were launched on
satellites
A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotop ...
since the 1970s. TSI measurements varied from 1355 to 1375 W/m
2 across more than ten satellites. One of the satellites, the
ACRIMSAT
The Active Cavity Radiometer Irradiance Monitor Satellite, or ACRIMSAT was a satellite carrying the ACRIM-3 (Active Cavity Radiometer Irradiance Monitor 3) instrument. It was one of the 21 observational components of NASA's Earth Observing Syst ...
was launched by the ACRIM group. The controversial 1989–1991 "ACRIM gap" between non-overlapping ACRIM satellites was interpolated by the ACRIM group into a composite showing +0.037%/decade rise. Another series based on the ACRIM data is produced by the PMOD group and shows a −0.008%/decade downward trend. This 0.045%/decade difference can impact climate models. However, reconstructed total solar irradiance with models favor the PMOD series, thus reconciling the ACRIM-gap issue.
Solar irradiance varies systematically over the cycle, both in total irradiance and in its relative components (UV vs visible and other frequencies). The
solar luminosity is an estimated 0.07 percent brighter during the mid-cycle solar maximum than the terminal solar minimum.
Photospheric
The photosphere is a star's outer shell from which light is radiated.
The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it ...
magnetism appears to be the primary cause (96%) of 1996–2013 TSI variation. The ratio of ultraviolet to visible light varies.
TSI varies in phase with the solar magnetic activity cycle with an amplitude of about 0.1% around an average value of about 1361.5 W/m
2 (the "
solar constant
The solar constant (''GSC'') is a flux density measuring mean solar electromagnetic radiation (total solar irradiance) per unit area. It is measured on a surface perpendicular to the rays, one astronomical unit (au) from the Sun (roughly the ...
"). Variations about the average of up to −0.3% are caused by large sunspot groups and of +0.05% by large
faculae
A facula (plural: faculae ), Latin for "little torch", is literally a "bright spot". The term has several common technical uses. It is used in planetary nomenclature for naming certain surface features of planets and moons,. and is also a type of ...
and the bright network on a 7-10-day timescale (see TSI variation graphics).
Satellite-era TSI variations show small but detectable trends.
TSI is higher at solar maximum, even though sunspots are darker (cooler) than the average photosphere. This is caused by magnetized structures other than sunspots during solar maxima, such as faculae and active elements of the "bright" network, that are brighter (hotter) than the average photosphere. They collectively overcompensate for the irradiance deficit associated with the cooler, but less numerous sunspots. The primary driver of TSI changes on solar rotational and solar cycle timescales is the varying photospheric coverage of these radiatively active solar magnetic structures.
Energy changes in UV irradiance involved in production and loss of
ozone
Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...
have atmospheric effects. The 30
hPa HPA may refer to:
Organizations
* Harry Potter Alliance, a charity
* Halifax Port Authority, Canada
* Hamburg Port Authority, Germany
* Hawaii Preparatory Academy, a school in Hawaii, US
* Health Protection Agency, UK
* Heerespersonalamt, the Ger ...
atmospheric pressure level changed height in phase with solar activity during solar cycles 20–23. UV irradiance increase caused higher ozone production, leading to stratospheric heating and to poleward displacements in the
stratospheric
The stratosphere () is the second layer of the atmosphere of the Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air hi ...
and
tropospheric
The troposphere is the first and lowest layer of the atmosphere of the Earth, and contains 75% of the total mass of the planetary atmosphere, 99% of the total mass of water vapour and aerosols, and is where most weather phenomena occur. From ...
wind systems.
Short-wavelength radiation
![The Solar Cycle XRay hi](https://upload.wikimedia.org/wikipedia/commons/c/c2/The_Solar_Cycle_XRay_hi.jpg)
With a temperature of 5870 K, the
photosphere
The photosphere is a star's outer shell from which light is radiated.
The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it ...
emits a proportion of radiation in the
extreme ultraviolet (EUV) and above. However, hotter upper layers of the Sun's atmosphere (
chromosphere
A chromosphere ("sphere of color") is the second layer of a star's atmosphere, located above the photosphere and below the solar transition region and corona. The term usually refers to the Sun's chromosphere, but not exclusively.
In the Su ...
and
corona) emit more short-wavelength radiation. Since the upper atmosphere is not homogeneous and contains significant magnetic structure, the solar ultraviolet (UV),
EUV and X-ray flux varies markedly over the cycle.
The photo montage to the left illustrates this variation for soft
X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
, as observed by the Japanese satellite
Yohkoh from after August 30, 1991, at the peak of cycle 22, to September 6, 2001, at the peak of cycle 23. Similar cycle-related variations are observed in the flux of solar UV or EUV radiation, as observed, for example, by the
SOHO
Soho is an area of the City of Westminster, part of the West End of London. Originally a fashionable district for the aristocracy, it has been one of the main entertainment districts in the capital since the 19th century.
The area was develop ...
or
TRACE
Trace may refer to:
Arts and entertainment Music
* Trace (Son Volt album), ''Trace'' (Son Volt album), 1995
* Trace (Died Pretty album), ''Trace'' (Died Pretty album), 1993
* Trace (band), a Dutch progressive rock band
* The Trace (album), ''The ...
satellites.
Even though it only accounts for a minuscule fraction of total solar radiation, the impact of solar UV, EUV and X-ray radiation on the Earth's upper atmosphere is profound. Solar UV flux is a major driver of
stratospheric chemistry, and increases in ionizing radiation significantly affect
ionosphere
The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an ...
-influenced temperature and
electrical conductivity
Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allow ...
.
Solar radio flux
Emission from the Sun at centimetric (radio) wavelength is due primarily to coronal plasma trapped in the magnetic fields overlying active regions. The F10.7 index is a measure of the solar radio flux per unit frequency at a wavelength of 10.7 cm, near the peak of the observed solar radio emission. F10.7 is often expressed in SFU or
solar flux units The solar flux unit (sfu) is a convenient measure of spectral flux density often used in solar radio observations, such as the F10.7 solar activity index:
:1 sfu = 104 Jy = 10−22 W⋅m−2⋅Hz−1 = 10−19 erg⋅s−1⋅cm−2⋅Hz ...
(1 SFU = 10
−22 W m
−2 Hz
−1). It represents a measure of diffuse, nonradiative coronal plasma heating. It is an excellent indicator of overall solar activity levels and correlates well with solar UV emissions.
Sunspot activity has a major effect on long distance
radio communications, particularly on the
shortwave
Shortwave radio is radio transmission using shortwave (SW) radio frequencies. There is no official definition of the band, but the range always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (100 to 10 me ...
bands although medium wave and low
VHF
Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter.
Frequencies immediately below VHF ...
frequencies are also affected. High levels of sunspot activity lead to improved signal propagation on higher frequency bands, although they also increase the levels of solar noise and ionospheric disturbances. These effects are caused by impact of the increased level of solar radiation on the
ionosphere
The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an ...
.
10.7 cm solar flux could interfere with point-to-point terrestrial communications.
Clouds
Speculations about the effects of cosmic-ray changes over the cycle potentially include:
* Changes in ionization affect the aerosol abundance that serves as the condensation nucleus for cloud formation.
During solar minima more cosmic rays reach Earth, potentially creating ultra-small aerosol particles as precursors to
Cloud condensation nuclei
Cloud condensation nuclei (CCNs), also known as cloud seeds, are small particles typically 0.2 µm, or one hundredth the size of a cloud droplet. CCNs are a unique subset of aerosols in the atmosphere on which water vapour condenses. This c ...
.
[
] Clouds formed from greater amounts of condensation nuclei are brighter, longer lived and likely to produce less precipitation.
* A change in cosmic rays could cause an increase in certain types of clouds, affecting Earth's
albedo
Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...
.
* It was proposed that, particularly at high
latitude
In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...
s, cosmic ray variation may impact terrestrial low altitude cloud cover (unlike a lack of correlation with high altitude clouds), partially influenced by the solar-driven interplanetary magnetic field (as well as passage through the galactic arms over longer timeframes),
but this hypothesis was not confirmed.
Later papers showed that production of clouds via cosmic rays could not be explained by nucleation particles. Accelerator results failed to produce sufficient, and sufficiently large, particles to result in cloud formation; this includes observations after a major solar storm.
Observations after
Chernobyl
Chernobyl ( , ; russian: Чернобыль, ) or Chornobyl ( uk, Чорнобиль, ) is a partially abandoned city in the Chernobyl Exclusion Zone, situated in the Vyshhorod Raion of northern Kyiv Oblast, Ukraine. Chernobyl is about no ...
do not show any induced clouds.
Terrestrial
Organisms
The impact of the solar cycle on living organisms has been investigated (see
chronobiology
Chronobiology is a field of biology that examines timing processes, including periodic (cyclic) phenomena in living organisms, such as their adaptation to solar- and lunar-related rhythms. These cycles are known as biological rhythms. Chronobi ...
). Some researchers claim to have found connections with human health.
The amount of ultraviolet UVB light at 300 nm reaching the Earth's surface varies by a few percent over the solar cycle due to variations in the protective
ozone layer
The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the atmosphere, although still small in rela ...
. In the stratosphere,
ozone
Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...
is
continuously regenerated by the
splitting
Splitting may refer to:
* Splitting (psychology)
* Lumpers and splitters, in classification or taxonomy
* Wood splitting
* Tongue splitting
* Splitting, railway operation
Mathematics
* Heegaard splitting
* Splitting field
* Splitting principle
* ...
of
O2 molecules by ultraviolet light. During a solar minimum, the decrease in ultraviolet light received from the Sun leads to a decrease in the concentration of ozone, allowing increased UVB to reach the Earth's surface.
Radio communication
Skywave modes of radio communication operate by bending (
refracting
In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomeno ...
) radio waves (
electromagnetic radiation
In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic field, electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, inf ...
) through the
Ionosphere
The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an ...
. During the "peaks" of the solar cycle, the ionosphere becomes increasingly ionized by solar photons and
cosmic rays
Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
. This affects the
propagation
Propagation can refer to:
*Chain propagation in a chemical reaction mechanism
*Crack propagation, the growth of a crack during the fracture of materials
*Propaganda, non-objective information used to further an agenda
*Reproduction, and other forms ...
of the radio wave in complex ways that can either facilitate or hinder communications. Forecasting of skywave modes is of considerable interest to commercial
marine
Marine is an adjective meaning of or pertaining to the sea or ocean.
Marine or marines may refer to:
Ocean
* Maritime (disambiguation)
* Marine art
* Marine biology
* Marine debris
* Marine habitats
* Marine life
* Marine pollution
Military
* ...
and
aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...
communications
Communication (from la, communicare, meaning "to share" or "to be in relation with") is usually defined as the transmission of information. The term may also refer to the message communicated through such transmissions or the field of inquir ...
,
amateur radio operators and
shortwave
Shortwave radio is radio transmission using shortwave (SW) radio frequencies. There is no official definition of the band, but the range always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (100 to 10 me ...
broadcasters
Broadcaster may refer to:
* A presenter of any syndicated media program
* A broadcasting organization, one responsible for audio and video content and/or their transmission
* A sports commentator on television or radio
* Broadcaster, currently kn ...
. These users occupy frequencies within the
High Frequency
High frequency (HF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten ...
or 'HF' radio spectrum that are most affected by these solar and ionospheric variances. Changes in solar output affect the
maximum usable frequency, a limit on the highest
frequency
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
usable for communications.
Climate
Both long-term and short-term variations in solar activity are proposed to potentially affect global climate, but it has proven challenging to show any link between solar variation and climate.
[Joanna D. Haigh]
The Sun and the Earth's Climate
, ''Living Reviews in Solar Physics'' (access date 31 January 2012)
Early research attempted to correlate weather with limited success,
followed by attempts to correlate solar activity with global temperature. The cycle also impacts regional climate. Measurements from the SORCE's Spectral Irradiance Monitor show that solar UV variability produces, for example, colder winters in the U.S. and northern Europe and warmer winters in Canada and southern Europe during solar minima.
Three proposed mechanisms mediate solar variations' climate impacts:
* Total solar irradiance ("
Radiative forcing
Radiative forcing (or climate forcing) is the change in energy flux in the atmosphere caused by natural or anthropogenic factors of climate change as measured by watts / metre2. It is a scientific concept used to quantify and compare the external ...
").
* Ultraviolet irradiance. The UV component varies by more than the total, so if UV were for some (as yet unknown) reason having a disproportionate effect, this might affect climate.
* Solar wind-mediated galactic
cosmic ray
Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
changes, which may affect cloud cover.
The solar cycle variation of 0.1% has small but detectable effects on the Earth's climate. Camp and Tung suggest that solar irradiance correlates with a variation of 0.18 K ±0.08 K (0.32 °F ±0.14 °F) in measured average global temperature between solar maximum and minimum.
Other effects include one study which found a relationship with wheat prices, and another one that found a weak correlation with the flow of water in the
Paraná River
The Paraná River ( es, Río Paraná, links=no , pt, Rio Paraná, gn, Ysyry Parana) is a river in south-central South America, running through Brazil, Paraguay, and Argentina for some ."Parana River". Encyclopædia Britannica. Encyclopædia Br ...
. Eleven-year cycles have been found in tree-ring thicknesses
[ and layers at the bottom of a lake][ hundreds of millions of years ago.
The current scientific consensus, most specifically that of the IPCC, is that solar variations only play a marginal role in driving ]global climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
, since the measured magnitude of recent solar variation is much smaller than the forcing due to greenhouse gases.[; see also the IPCC Fourth Assessment Report, in which the magnitude of variation in solar irradiance was revised downward, although the evidence of connections between solar variation and certain aspects of climate increased over the same time period]
Assessment Report-4, Working group 1, chapter 2
Also, average solar activity in the 2010s was no higher than in the 1950s (see above), whereas average global temperatures had risen markedly over that period. Otherwise, the level of understanding of solar impacts on weather is low.
Solar variations also affect the orbital decay
Orbital decay is a gradual decrease of the distance between two orbiting bodies at their closest approach (the periapsis) over many orbital periods. These orbiting bodies can be a planet and its satellite, a star and any object orbiting it, or ...
of objects in low Earth orbit
A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never mor ...
(LEO) by altering the density of the upper thermosphere
The thermosphere is the layer in the Earth's atmosphere directly above the mesosphere and below the exosphere. Within this layer of the atmosphere, ultraviolet radiation causes photoionization/photodissociation of molecules, creating ions; the ...
.
Solar dynamo
The 11-year solar cycle is thought to be one-half of a 22-year Babcock–Leighton solar dynamo cycle, which corresponds to an oscillatory exchange of energy between toroidal and poloidal solar magnetic fields which is mediated by solar plasma flows which also provides energy to the dynamo system at every step. At solar-cycle maximum, the external poloidal dipolar magnetic field is near its dynamo-cycle minimum strength, but an internal toroidal quadrupolar field, generated through differential rotation within the tachocline
The tachocline is the transition region of stars of more than 0.3 solar masses, between the radiative interior and the differentially rotating outer convective zone. This causes the region to have a very large shear as the rotation rate change ...
, is near its maximum strength. At this point in the dynamo cycle, buoyant upwelling within the Convection zone forces emergence of the toroidal magnetic field through the photosphere, giving rise to pairs of sunspots, roughly aligned east–west with opposite magnetic polarities. The magnetic polarity of sunspot pairs alternates every solar cycle, a phenomenon described by Hale's law
In solar physics, Hale's law, also known as Hale's polarity law or the Hale–Nicholson law, describes the tendency for bipolar active regions within the same northern or southern hemisphere to have the same leading magnetic polarity with respect ...
.
During the solar cycle's declining phase, energy shifts from the internal toroidal magnetic field to the external poloidal field, and sunspots diminish in number. At solar minimum, the toroidal field is, correspondingly, at minimum strength, sunspots are relatively rare and the poloidal field is at maximum strength. During the next cycle, differential rotation converts magnetic energy back from the poloidal to the toroidal field, with a polarity that is opposite to the previous cycle. The process carries on continuously, and in an idealized, simplified scenario, each 11-year sunspot cycle corresponds to a change in the polarity of the Sun's large-scale magnetic field.
Solar dynamo models indicate that plasma flux transport processes in the solar interior such as differential rotation, meridional circulation and turbulent pumping play an important role in the recycling of the toroidal and poloidal components of the solar magnetic field
Hazra and Nandy 2016
. The relative strengths of these flux transport processes also determine the "memory" of the solar cycle that plays an important role in physics-based predictions of the solar cycle
Yeates, Nandy and Mackay (2008)
an
Karak and Nandy (2012)
in particular, utilized stochastically forced non-linear solar dynamo simulations to establish that the solar cycle memory is short, lasting over one cycle, thus implying accurate predictions are possible only for the next solar cycle and not beyond. This postulate of a short one cycle memory in the solar dynamo mechanism was later observationally verified b
Muñoz-Jaramillo et al. (2013)
Although the tachocline
The tachocline is the transition region of stars of more than 0.3 solar masses, between the radiative interior and the differentially rotating outer convective zone. This causes the region to have a very large shear as the rotation rate change ...
has long been thought to be the key to generating the Sun's large-scale magnetic field, recent research has questioned this assumption. Radio observations of brown dwarfs
Brown dwarfs (also called failed stars) are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen ( 1H) into helium in their cores, unlike a main-sequence star. Instead, they have a mass between the most m ...
have indicated that they also maintain large-scale magnetic fields and may display cycles of magnetic activity. The Sun has a radiative core surrounded by a convective envelope, and at the boundary of these two is the tachocline
The tachocline is the transition region of stars of more than 0.3 solar masses, between the radiative interior and the differentially rotating outer convective zone. This causes the region to have a very large shear as the rotation rate change ...
. However, brown dwarfs lack radiative cores and tachoclines. Their structure consists of a solar-like convective envelope that exists from core to surface. Since they lack a tachocline
The tachocline is the transition region of stars of more than 0.3 solar masses, between the radiative interior and the differentially rotating outer convective zone. This causes the region to have a very large shear as the rotation rate change ...
yet still display solar-like magnetic activity, it has been suggested that solar magnetic activity is only generated in the convective envelope.
Speculated influence of the planets
It has long been theorized that the planets may have an influence on the solar cycle, with many speculative papers published. For example, a 2012 paper proposed that the torque exerted by the planets on a non-spherical tachocline
The tachocline is the transition region of stars of more than 0.3 solar masses, between the radiative interior and the differentially rotating outer convective zone. This causes the region to have a very large shear as the rotation rate change ...
layer deep in the Sun may synchronize the solar dynamo. However, their results were shown to be an artifact of the incorrectly applied smoothing method leading to aliasing. Additional models incorporating the influence of planetary forces on the Sun have since been proposed. However, the solar variability is known to be essentially stochastic and unpredictable beyond one solar cycle, which contradicts the idea of the deterministic planetary influence on solar dynamo. Moreover, modern dynamo models are able to reproduce the solar cycle without any planetary influence. Accordingly, the planetary influence on the solar dynamo is considered marginal and contradicting the ''Occam's razor
Occam's razor, Ockham's razor, or Ocham's razor ( la, novacula Occami), also known as the principle of parsimony or the law of parsimony ( la, lex parsimoniae), is the problem-solving principle that "entities should not be multiplied beyond neces ...
'' principles.
In 1974, the best-selling book ''The Jupiter Effect
''The Jupiter Effect'' is a 1974 book by John Gribbin and Stephen Plagemann, in which the authors predicted that an alignment of the planets of the Solar System would create a number of catastrophes, including a great earthquake on the San Andreas ...
'' was published based on the idea that the alignment of the planets would alter the Sun's solar wind and, in turn, Earth's weather. The book predicted a number of catastrophic events, all of which failed to occur.
See also
References
General references
*
*
*
*
*
*
*
External links
* NOAA / NESDIS / NGDC (2002
Solar Variability Affecting Earth
NOAA CD-ROM NGDC-05/01. This CD-ROM contains over 100 solar-terrestrial and related global data bases covering the period through April 1990.
*
*
updated every Monday
Satellite Total Solar Irradiance Observations
SolarCycle24.com
Solar Physics Web Pages
at NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding t ...
's Marshall Space Flight Center
The George C. Marshall Space Flight Center (MSFC), located in Redstone Arsenal, Alabama (Huntsville postal address), is the U.S. government's civilian rocketry and spacecraft propulsion research center. As the largest NASA center, MSFC's first ...
Science Briefs: Do Variations in the Solar Cycle Affect Our Climate System?
By David Rind, NASA GISS, January 2009
Yohkoh Public Outreach Project
Stanford Solar Center
NASA's Cosmos
SOHO Web Site
Solar Influences Data Analysis Center
(University of South Wales)
*
* ttp://sunspotwatch.com/ SunSpotWatch.com (since 1999)
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