Sunspots are temporary phenomena on the Sun's photosphere that appear as spots darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic field flux that inhibit convection. Sunspots usually appear in pairs of opposite magnetic polarity. Their number varies according to the approximately 11-year solar cycle.
Individual sunspots or groups of sunspots may last anywhere from a few days to a few months, but eventually decay. Sunspots expand and contract as they move across the surface of the Sun, with diameters ranging from 16 km (10 mi) to 160,000 km (100,000 mi). The larger variety are visible from Earth without the aid of a telescope. They may travel at relative speeds, or proper motions, of a few hundred meters per second when they first emerge.
Indicating intense magnetic activity, sunspots accompany secondary phenomena such as coronal loops, prominences, and reconnection events. Most solar flares and coronal mass ejections originate in magnetically active regions around visible sunspot groupings. Similar phenomena indirectly observed on stars other than the Sun are commonly called starspots, and both light and dark spots have been measured.
The earliest extant report of sunspots dates back to the Chinese Book of Changes, c. 800 BC. The first clear mention of a sunspot in Western literature, around 300 BC, was by the ancient Greek scholar Theophrastus, student of Plato and Aristotle and successor to the latter. The earliest surviving record of deliberate 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. Sunspots were first observed telescopically in late 1610 by English astronomer Thomas Harriot and Frisian astronomers Johannes and David Fabricius, who published a description in June 1611.
Although they are at temperatures of roughly 3,000–4,500 K (2,700–4,200 °C), the contrast with the surrounding material at about 5,780 K (5,500 °C) leaves sunspots clearly visible as dark spots. This is because the luminance (which is essentially "brightness" in visible light) of a heated black body (closely approximated by the photosphere) at these temperatures varies extremely with temperature—considerably more so than the (temperature to the fourth power) variation in the total black-body radiation at all wavelengths (see Stefan–Boltzmann law). Isolated from the surrounding photosphere a sunspot would be brighter than the Moon.
Sunspots have two parts: the central umbra, which is the darkest part, where the magnetic field is approximately vertical (normal to the Sun's surface) and the surrounding penumbra, which is lighter, where the magnetic field is more inclined.
Any given appearance of a sunspot may last anywhere from a few days to a few months, though groups of sunspots and their active regions tend to last weeks or months, but all do eventually decay and disappear. Sunspots expand and contract as they move across the surface of the Sun, with diameters ranging from 16 km (10 mi) to 160,000 km (100,000 mi).
Although the details of sunspot generation are still a matter of research, it appears that sunspots are the visible counterparts of magnetic flux tubes in the Sun's convective zone that get "wound up" by differential rotation. If the stress on the tubes reaches a certain limit, they curl up and puncture the Sun's surface. Convection is inhibited at the puncture points; the energy flux from the Sun's interior decreases, and with it, surface temperature.
The Wilson effect implies that sunspots are depressions on the Sun's surface. Observations using the Zeeman effect show that prototypical sunspots come in pairs with opposite magnetic polarity. From cycle to cycle, the polarities of leading and trailing (with respect to the solar rotation) sunspots change from north/south to south/north and back. Sunspots usually appear in groups.
Magnetic pressure should tend to remove field concentrations, causing the sunspots to disperse, but sunspot lifetimes are measured in days to weeks. In 2001, observations from the Solar and Heliospheric Observatory (SOHO) using sound waves traveling below the photosphere (local helioseismology) were used to develop a three-dimensional image of the internal structure below sunspots; these observations show that a powerful downdraft underneath each sunspot, forms a rotating vortex that sustains the concentrated magnetic field.
Sunspot activity cycles are about every eleven years, with some variation in length. Over the solar cycle, sunspot populations rise quickly and then fall more slowly. The point of highest sunspot activity during a cycle is known as solar maximum, and the point of lowest activity as solar minimum. This period is also observed in most other solar activity and is linked to a variation in the solar magnetic field that changes polarity with this period.
Early in the cycle, sunspots appear in the higher latitudes and then move towards the equator as the cycle approaches maximum, following Spörer's law. Spots from two adjacent cycles can co-exist for some time. Spots from adjacent cycles can be distinguished by direction of their magnetic field.
The Wolf number sunspot index counts the average number of sunspots and groups of sunspots during specific intervals. The 11-year solar cycles are numbered sequentially, starting with the observations made in the 1750s.
George Ellery Hale first linked magnetic fields and sunspots in 1908. Hale suggested that the sunspot cycle period is 22 years, covering two periods of increased and decreased sunspot numbers, accompanied by polar reversals of the solar magnetic dipole field. Horace W. Babcock later proposed a qualitative model for the dynamics of the solar outer layers. The Babcock Model explains that magnetic fields cause the behavior described by Spörer's law, as well as other effects, which are twisted by the Sun's rotation.
Sunspot number also changes over long periods. For example, from 1900 to the 1960s, the solar maxima trend of sunspot count was upwards; for the following decades it diminished. However, the Sun was last as active as this period over 8,000 years ago.
Sunspots number is correlated with the intensity of solar radiation over the period since 1979, when satellite measurements became available. The variation caused by the sunspot cycle to solar output is relatively small, on the order of 0.1% of the solar constant (a peak-to-trough range of 1.3 W·m−2 compared with 1366 W·m−2 for the average solar constant).
400-year history of sunspot numbers, showing Maunder and Dalton minima, and the Modern Maximum (left) and 11,000-year sunspot reconstruction showing a downward trend over 2000 BC – 1600 AD followed by the recent 400 year uptrend
Sunspots are observed with land-based and Earth-orbiting solar telescopes. These telescopes use filtration and projection techniques for direct observation, in addition to various types of filtered cameras. Specialized tools such as spectroscopes and spectrohelioscopes are used to examine sunspots and sunspot areas. Artificial eclipses allow viewing of the circumference of the Sun as sunspots rotate through the horizon.
Since looking directly at the Sun with the naked eye permanently damages human vision, amateur observation of sunspots is generally conducted using projected images, or directly through protective filters. Small sections of very dark filter glass, such as a #14 welder's glass, are effective. A telescope eyepiece can project the image, without filtration, onto a white screen where it can be viewed indirectly, and even traced, to follow sunspot evolution. Special purpose hydrogen-alpha narrow bandpass filters and aluminum-coated glass attenuation filters (which have the appearance of mirrors due to their extremely high optical density) on the front of a telescope provide safe observation through the eyepiece.
Due to its link to other kinds of solar activity, sunspot occurrence can be used to help predict space weather, the state of the ionosphere, and hence the conditions of short-wave radio propagation or satellite communications. Solar activity (and the solar cycle) have been implicated in global warming, originally the role of the Maunder Minimum of sunspot occurrence in the Little Ice Age in European winter climate. Sunspots themselves, in terms of the magnitude of their radiant-energy deficit, have a weak effect on terrestrial climate in a direct sense. On longer time scales, such as the solar cycle, other magnetic phenomena (faculae and the chromospheric network) correlate with sunspot occurrence.
In 1947, G. E. Kron proposed that starspots were the reason for periodic changes in brightness on red dwarfs. Since the mid-1990s, starspot observations have been made using increasingly powerful techniques yielding more and more detail: photometry showed starspot growth and decay and showed cyclic behavior similar to the Sun's; spectroscopy examined the structure of starspot regions by analyzing variations in spectral line splitting due to the Zeeman effect; Doppler imaging showed differential rotation of spots for several stars and distributions different from the Sun's; spectral line analysis measured the temperature range of spots and the stellar surfaces. For example, in 1999, Strassmeier reported the largest cool starspot ever seen rotating the giant K0 star XX Triangulum (HD 12545) with a temperature of 3,500 K (3,230 °C), together with a warm spot of 4,800 K (4,530 °C).
starspots vary on the same (short) time scales as Sunspots do ... HD 12545 had a warm spot (350 K above photospheric temperature; the white area in the picture)
The Apache Point Observatory (APO; obs. code: 705) is an astronomical observatory located in the Sacramento Mountains in Sunspot, New Mexico, United States, approximately 18 miles (29 km) south of Cloudcroft. The observatory is operated by New Mexico State University (NMSU) and owned by the Astrophysical Research Consortium (ARC). Access to the telescopes and buildings is private and restricted.During the 2018 closure of Sunspot, Apache Point Observatory remained open, although court documents later showed that the accused was employed at Apache Point Observatory.Arthur Covington
Arthur Edwin Covington (21 September 1913 – 17 March 2001) was a Canadian physicist who made the first radio astronomy measurements in Canada. Through these he made the valuable discovery that sunspots generate large amounts of microwaves at the 10.7 cm wavelength, offering a simple all-weather method to measure and predict sunspot activity, and their associated effects on communications. The sunspot detection program has run continuously to this day.Cathey Peak
Cathey Peak is a peak in the Sacramento Mountains, in the south-central part of the U.S. State of New Mexico. It lies in Otero County, 10 miles (16 km) southeast of the community of Alamogordo.
Sacramento Peak, at 9,262 feet (2,823 m), is a nearby subpeak of Cathey Peak, and is more widely known due to the presence of several observatories on or near its summit. It is located at 32°47′16″N 105°49′15″W, 1.6 miles (2.6 km) southwest of Cathey Peak, and has a topographic prominence of approximately 80 feet (24 m). The Sunspot Solar Observatory is on the summit itself, and the site of this observatory incorporates the small town of Sunspot, less than one-half mile (0.8 km) to the northeast. The Apache Point Observatory is located on a promontory about one-half mile (0.8 km) south of the summit.
Both peaks lie on the high western crest of the Sacramento Mountains, and hence have gentle, forested eastern slopes, and a steep, high escarpment to the west, descending to the Tularosa Basin. Both peaks can be accessed using New Mexico Scenic Byway 6563 from Cloudcroft.Coronal mass ejection
A coronal mass ejection (CME) is a significant release of plasma and accompanying magnetic field from the solar corona. They often follow solar flares and are normally present during a solar prominence eruption. The plasma is released into the solar wind, and can be observed in coronagraph imagery.Coronal mass ejections are often associated with other forms of solar activity, but a broadly accepted theoretical understanding of these relationships has not been established. CMEs most often originate from active regions on the Sun's surface, such as groupings of sunspots associated with frequent flares. Near solar maxima, the Sun produces about three CMEs every day, whereas near solar minima, there is about one CME every five days.List of solar cycles
The following is a list of solar cycles (sometimes called sunspot cycles), tracked since 1755 following the original numbering proposed by Rudolf Wolf in the mid-19th century The source data are the revised International Sunspot Numbers (ISN v2.0), as available at SILSO.
Sunspot number counts exist since 1610 but the cycle numbering is not well defined during the Maunder minimum. It was proposed that one cycle might have been lost in the late 18th century, but this still remains not fully confirmed.
The smoothing was done using the traditional SIDC smoothing formula. Other smoothing formulas exist, and they usually give slightly different values for the amplitude and timings of the solar cycles. An example is the Meeus smoothing formula, with related solar cycles characteristics available in this STCE news item.In the table below, the number of spotless days is the number between the maximum of the previous solar cycle and the maximum of the new solar cycle. As an example, there were 817 spotless days during the transit from solar cycle 23 to solar cycle 24.Man-in-the-browser
Man-in-the-browser (MITB, MitB, MIB, MiB), a form of Internet threat related to man-in-the-middle (MITM), is a proxy Trojan horse that infects a web browser by taking advantage of vulnerabilities in browser security to modify web pages, modify transaction content or insert additional transactions, all in a completely covert fashion invisible to both the user and host web application. A MitB attack will be successful irrespective of whether security mechanisms such as SSL/PKI and/or two or three-factor Authentication solutions are in place. A MitB attack may be countered by using out-of-band transaction verification, although SMS verification can be defeated by man-in-the-mobile (MitMo) malware infection on the mobile phone. Trojans may be detected and removed by antivirus software with a 23% success rate against Zeus in 2009, and still low rates in 2011. The 2011 report concluded that additional measures on top of antivirus were needed. A related, simpler attack is the boy-in-the-browser (BitB, BITB). The majority of financial service professionals in a survey considered MitB to be the greatest threat to online banking.Maunder Minimum
The Maunder Minimum, also known as the "prolonged sunspot minimum", is the name used for the period around 1645 to 1715 during which sunspots became exceedingly rare, as was then noted by solar observers.
The term was introduced after John A. Eddy published a landmark 1976 paper in Science. Astronomers before Eddy had also named the period after the solar astronomers Annie Russell Maunder (1868–1947) and her husband, Edward Walter Maunder (1851–1928), who studied how sunspot latitudes changed with time. The period which the spouses examined included the second half of the 17th century.
Two papers were published in Edward Maunder's name in 1890 and 1894, and he cited earlier papers written by Gustav Spörer. Because Annie Maunder had not received a university degree, restrictions at the time caused her contribution not to be publicly recognized.Spörer noted that, during a 28-year period (1672–1699) within the Maunder Minimum, observations revealed fewer than 50 sunspots.
This contrasts with the typical 40000 – 50000 sunspots seen in modern times (over similar 25 year sampling).Like the Homeric Minimum, Dalton Minimum and the Spörer Minimum, the Maunder Minimum coincided with a period of lower-than-average European temperatures.Solar cycle
The solar cycle or solar magnetic activity cycle is the nearly periodic 11-year change in the Sun's activity (including changes in the levels of solar radiation and ejection of solar material) and appearance (changes in the number and size of sunspots, flares, and other manifestations).
They have been observed (by changes in the Sun's appearance and by changes seen on Earth, such as auroras) for centuries.
The changes on the Sun cause effects in space, in the atmosphere, and on Earth's surface. While it is the dominant variable in solar activity, aperiodic fluctuations also occur.Solar cycle 24
Solar Cycle 24 is the 24th solar cycle since 1755, when extensive recording of solar sunspot activity began. It is the current solar cycle, and began in December 2008 with a smoothed minimum of 2.2 (SIDC formula). Activity was minimal until early 2010. It reached its maximum in April 2014 with a smoothed sunspot number of only 81.8, the lowest since the Dalton Minimum (early 1800s). Reversed polarity polar active sunspot regions in December 2016, April 2018, and November 2018 indicate that a transitional phase to solar cycle 25 is in process.Solar cycle 8
Solar cycle 8 was the eighth solar cycle since 1755, when extensive recording of solar sunspot activity began. The solar cycle lasted 9.7 years, beginning in November 1833 and ending in July 1843. The maximum smoothed sunspot number (SIDC formula) observed during the solar cycle was 244.9 (March 1837), and the starting minimum was 12.2.Solar cycle #8 ended in 1843, the year that Heinrich Schwabe discovered the sunspot cycle.Solar flare
A solar flare is a sudden flash of increased brightness on the Sun, usually observed near its surface
and in close proximity to a sunspot group.
Powerful flares are often, but not always, accompanied by a coronal mass ejection. Even the most powerful flares are barely detectable in the total solar irradiance (the "solar constant").Solar flares occur in a power-law spectrum of magnitudes; an energy release of typically 1020 joules of energy suffices to produce a clearly observable event, while a major event can emit up to 1025 joules.Flares are closely associated with the ejection of plasmas and particles through the Sun's corona into outer space; flares also copiously emit radio waves.
If the ejection is in the direction of the Earth, particles associated with this disturbance can penetrate into the upper atmosphere (the ionosphere) and cause bright auroras, and may even disrupt long range radio communication.
It usually takes days for the solar plasma ejecta to reach Earth. Flares also occur on other stars, where the term stellar flare applies.
High-energy particles, which may be relativistic, can arrive almost simultaneously with the electromagnetic radiations.
On July 23, 2012, a massive, potentially damaging, solar storm (solar flare, coronal mass ejection and electromagnetic radiation) barely missed Earth. According to NASA, there may be as much as a 12% chance of a similar event occurring between 2012 and 2022.Solar maximum
Solar maximum or solar max is a regular period of greatest Sun activity during the 11-year solar cycle. During solar maximum, large numbers of sunspots appear, and the solar irradiance output grows by about 0.07%. The increased energy output of solar maxima can impact Earth's global climate, and recent studies have shown some correlation with regional weather patterns.At solar maximum, the Sun's magnetic field lines are the most distorted due to the magnetic field on the solar equator rotating at a slightly faster pace than at the solar poles. On average, the solar cycle takes about 11 years to go from one solar maximum to the next, with duration observed varying from 9 to 14 years.
Large solar flares often occur during a maximum. For example, the solar storm of 1859 struck the Earth with such intensity that the northern lights were visible as far from the poles as Cuba and Hawaii.Solar minimum
Solar minimum is the period of least solar activity in the 11 year solar cycle of the Sun. During this time, sunspot and solar flare activity diminishes, and often does not occur for days at a time. The date of the minimum is described by a smoothed average over 12 months of sunspot activity, so identifying the date of the solar minimum usually can only happen 6 months after the minimum takes place. Solar minima are generally correlated with changes in climate and recent studies have shown a correlation with regional weather patterns.
Solar minimum is contrasted with the solar maximum, where there may be hundreds of sunspots.Solar observation
Solar observation is the scientific endeavor of studying the Sun and its behavior and relation to the Earth and the remainder of the Solar System. Deliberate solar observation began thousands of years ago. That initial era of direct observation gave way to telescopes in the 1600s followed by satellites in the twentieth century.Sunspot, New Mexico
Sunspot is an unincorporated community, located in the Sacramento Mountains, in Otero County, New Mexico, United States. It is located within the Lincoln National Forest, 18 miles south of Cloudcroft. Its elevation is 9200 feet. The Sunspot Solar Observatory is located in Sunspot in the Sacramento Mountains. On Oct 31 2018, Sunspot Solar Observatory took over the operations of the science from Dunn Solar Telescope and Visitors Center, although AURA maintained operations of the Sunspot site. The telescope and site is open to the public, and the visitors center offers guided tours of the site on Saturdays and Sundays. On other days there is a self-guided 1/2 mile trail around the telescope and White Sands overlookSunspot (comics)
Sunspot (Roberto "Bobby" da Costa) is a fictional superhero appearing in American comic books published by Marvel Comics. The character is most commonly associated with X-Men-related groups the New Mutants and X-Force.
A mutant from Brazil, Sunspot possesses the ability to absorb and channel solar power. He is idealistic and impulsive, but is considered a close friend of many of his teammates. He was an important member of the X-Men's 1980s-era junior team and its reincarnation X-Force. He later retired his career as Sunspot and garnered a massive fortune, allowing him to buy out the organization Advanced Idea Mechanics, rebranding it Avengers Idea Mechanics, which he operates under the codename Citizen V.
In film, actor Adan Canto portrayed the character in X-Men: Days of Future Past. Henry Zaga will portray a younger version in The New Mutants.Sunspot Jonz
Corey Johnson, better known by his stage name Sunspot Jonz, is a rapper from Oakland, California. He is a founding member of Living Legends, a conglomerate of underground hip hop artists from California. He is also one half of Mystik Journeymen along with Luckyiam.Sunspots (economics)
In economics, the term sunspots (or sometimes "a sunspot") usually refers to an extrinsic random variable, that is, a random variable that does not affect economic fundamentals (such as endowments, preferences, or technology). Sunspots can also refer to the related concept of extrinsic uncertainty, that is, economic uncertainty that does not come from variation in economic fundamentals. David Cass and Karl Shell coined the term sunspots as a suggestive and less technical way of saying "extrinsic random variable".Wolf number
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.