Sunspot Observations Research Articles

Sunspot observations by Pehr Wargentin in Uppsala in 1747

This article reports on solar observations by Pehr Wargentin made in Uppsala in 1747. Drawings of the sun accompanied by textual annotations are preserved in the archives of the Royal Swedish Academy of Sciences. Numbers of sunspot groups, as well as sunspot numbers, were derived for March 1 to May 13, 1747 (Gregorian), the latter being approximations for some days as the exact number of spots and pores in large groups was not mentioned by Wargentin. Sunspot positions were also derived for the observing period, where reliable ones were obtained from right ascension and declination measurements by Wargentin and less accurate ones were measured in his drawings of the solar disk.

The association of the Hale sector boundary with RHESSI solar flares and active longitudes

Context. The heliospheric magnetic field (HMF) is structured into large sectors of positive and negative polarity. The parts of the boundary between these sectors where the change in polarity matches that of the leading-to-following sunspot polarity in that solar hemisphere, are called Hale sector boundaries (HSB). Aims. We investigate the flare occurrence rate near HSBs and the association between HSBs and active longitudes. Methods. Previous work determined the times HSBs were at solar central meridian, using the detection of the HMF sector boundary crossing at the Earth. In addition to this, we use a new approach which finds the HSB locations at all times by determining them from potential field source surface (PFSS) extrapolations of photospheric magnetograms. We use the RHESSI X-ray flare list for comparison to the HSB as it provides accurate flare locations over 14 years, from February 2002 to February 2016, covering both Cycles 23 and 24. For the active longitude positions we use previously published work based on sunspot observations. Results. We find that the two methods of determining the HSB generally agree and that 41% (Cycle 23) and 47% (Cycle 24) of RHESSI flares occur within 30° of the PFSS determined-HSB. The behaviour of the HSBs varies over the two Cycles studied, and as expected they swap in hemisphere as the Cycles change. The HSBs and active longitudes do overlap but not consistently. They often move at different rates relative to each other (and the Carrington solar rotation rate) and these vary over each Cycle. The HSBs provide a useful additional activity indicator, particularly during periods when active longitudes are difficult to determine.

A great space weather event in February 1730

Aims. Historical records provide evidence of extreme magnetic storms with equatorward auroral extensions before the epoch of systematic magnetic observations. One significant magnetic storm occurred on February 15, 1730. We scale this magnetic storm with auroral extension and contextualise it based on contemporary solar activity.Methods. We examined historical records in East Asia and computed the magnetic latitude (MLAT) of observational sites to scale magnetic storms. We also compared them with auroral records in Southern Europe. We examined contemporary sunspot observations to reconstruct detailed solar activity between 1729 and 1731.Results. We show 29 auroral records in East Asian historical documents and 37 sunspot observations.Conclusions. These records show that the auroral displays were visible at least down to 25.8° MLAT throughout East Asia. In comparison with contemporary European records, we show that the boundary of the auroral display closest to the equator surpassed 45.1° MLAT and possibly came down to 31.5° MLAT in its maximum phase, with considerable brightness. Contemporary sunspot records show an active phase in the first half of 1730 during the declining phase of the solar cycle. This magnetic storm was at least as intense as the magnetic storm in 1989, but less intense than the Carrington event.

Sunspot drawings by Japanese official astronomers in 1749–1750

AbstractSunspot observations with telescopes in the 18th century were carried out in Japan as well as elsewhere. One of these sunspot observations is recorded in an account called Sansaizusetsu narabini Kansei irai Jissoku Zusetsu (Charts of Three Worlds and Diagrams of Actual Observations since Kansei Era). We have analyzed manuscripts of this account to show a total of 15 sunspot drawings during 1749–1750. These observations are considered to be carried out by contemporary official astronomers in Japan, with telescopes covered by zongurasus (< zonglas in Dutch, corresponding to “sunglass” in English). We counted their group number of sunspots to locate them in long-term solar activity and show that their observations were situated near the solar maximum in 1750. We also computed their locations and areas, while we have to admit differences of the variant manuscripts with one another. These observational records show the spread of sunspot observations not only in Europe, but also in Japan, and hence may contribute to crosscheck, or possibly to improve the known sunspot indices.

Sunspot Observations Made by Hallaschka During the Dalton Minimum

We present and analyse the sunspot observations performed by Franz I. C. Hallaschka in 1814 and 1816. These solar observations were carried out during the so-called Dalton minimum, around the maximum phase of the Solar Cycle 6. These records are very valuable because they allow us to complete observational gaps in the collection of sunspot group numbers, improving its coverage for this epoch. We have analysed and compared the observations made by Hallaschka with the records made by other contemporary observers. Unfortunately, the analysis of the sunspot areas and positions showed that they are too inaccurate for scientific use. But, we conclude that sunspot counts made by Hallaschka are similar to those made by other astronomers of that time. The observations by Hallaschka confirm a low level of the solar activity during the Dalton minimum.

Inminente Hibernación Solar 2020

El Ciclo solar 23º, es el vigésimo tercer ciclo, registrado cuidadosamente desde que iniciaron las observaciones de manchas solares en occidente, en el siglo XVII. En este trabajo se pretende demostrar estadísticamente, la tendencia hacia una hibernación solar, donde pueden ser muchos años en que el Sol no produzca ninguna mancha solar, en este caso específico se estudió la actividad solar final del ciclo 23 y comienzos del ciclo 24. Planteando la tendencia de baja actividad en el Sol y que continuará por varios años, como se ha visto que sucedieron, en los cinco periodos, con espacios aproximados a 200 años o menos cada uno, diversos períodos excepcionales de baja actividad solar durante el último milenio. Estos períodos son: el de Norman (1010) el de Wolf (hacia el año 1300), Spoerer (1500), Maunder (1645 - 1715) y Dalton (1800-1830). Por lo que no resultaría extraño otro acontecimiento característico similar, en un futuro cercano; porque han transcurrido 186 años a la fecha, desde el último mínimo, el de Dalton desde el año 1800 a 1830. Se ha observado que la actividad solar, volvió a descender desde el año 2011 y ocurrió un pequeño rebrote en 2013. Así una buena parte de la comunidad científica espera que cuando finalice este ciclo 24 de manchas solares, es muy posible que el astro entre en hibernación. De seguir con la tendencia a la baja actividad solar, consecuentemente puede bajar la temperatura en nuestro planeta Tierra, como se ha visto en el pasado y arrojada por los resultados estadísticos de esta investigación.

Could a Hexagonal Sunspot Have Been Observed During the Maunder Minimum?

The Maunder Minimum was the period between 1645 and 1715 whose main characteristic was abnormally low and prolonged solar activity. However, some authors have doubted this low level of solar activity during that period by questioning the accuracy and objectivity of the observers. This work presents a particular case of a sunspot observed during the Maunder Minimum with an unusual shape of its umbra and penumbra: a hexagon. This sunspot was observed by Cassini in November 1676, just at the core of the Maunder Minimum. This historical observation is compared with a twin case that occurred recently in May 2016. The conclusion reached is that Cassini's record is another example of the good quality observations made during the Maunder Minimum, showing the meticulousness of the astronomers of that epoch. This sunspot observation made by Cassini does not support the conclusions of Zolotova and Ponyavin (Astrophys. J. 800, 42, 2015) that professional astronomers in the 17th century only registered round sunspots. Finally, a discussion is given of the importance of this kind of unusual sunspot record for a better assessment of the true level of solar activity in the Maunder Minimum.

Iwahashi Zenbei’s Sunspot Drawings in 1793 in Japan

Three Japanese sunspot drawings associated with Iwahashi Zenbei (1756-1811) are shown here from contemporary manuscripts and woodprint documents with the relevant texts. We revealed the observational date of one of the drawings to be 26 August 1793, and the overall observations lasted for over a year. Moreover, we identified the observational site for the dated drawing at Fushimi in Japan. We then compared his observations with group sunspot number and raw group count from Sunspot Index and Long-term Solar Observations (SILSO) to reveal its data context, and concluded that these drawings filled the gaps in understanding due to the fragmental sunspots observations around 1793. These drawings are important as a clue to evaluate astronomical knowledge of contemporary Japan in the late 19 th century and are valuable as a non-European observation, considering that most sunspot observations up to mid-19 th century are from Europe.

New sunspots and aurorae in the historical Chinese text corpus? Comments on uncritical digital search applications

We review some applications of the method of electronic searching for historical observations of sunspots and aurorae in the Chinese text corpus by Hayakawa et al. (, , , ), Kawamura et al. (), and Tamazawa et al. (). However, we show strong shortcomings in the digital search technique as applied by them: almost all likely true sunspot and aurora records were presented earlier (e.g., Xu et al. ), which are not mentioned in those papers; the remaining records are dubious and often refer to other phenomena, neither spots nor aurorae (this also applies to Hayakawa et al. ). The alleged aurorae in Hayakawa et al. () and Kawamura et al. () show a broad peak around full moon, not expected for aurorae. Hayakawa et al. () use the Korean report At night, the gate of heaven was opened (between AD 992 Dec 6 and AD 993 Jan 25, i.e., close to the 14C variation AD 993/994) to estimate the Dst index of solar activity, even though the text does not fulfill any discriminative aurora criteria (except night‐time). Most of the above publications include very few Chinese texts and translations, and their tables with abbreviated keywords do not allow the reader to consider alternative interpretations (the tables also do not specify which records mention night‐time). We have compared some of their event tables with previously published catalogues and found various discrepancies. There are also intrinsic inconsistencies, misleading information (lunar phase for day‐time events), and dating errors. We present Chinese texts and translations for some of their presumable new aurorae: only one can be considered a likely true aurora (AD 604 Jan); some others were selected on the sole basis of the use of the word light or rainbow. Several alleged new aurorae present observations beside the Sun during day‐time. There are well‐known comets among their presumable aurorae. We also discuss (a) whether heiqi ri pang can stand for black spot(s) on one side of or beside the sun, (b) the aurora color confusion in Hayakawa et al. (, ), and (c) whether white and unusual rainbows can be aurorae.

Possible Mesoamerican Naked-eye Observation of Sunspots - VI: Evidence from Yaxchilan Lintel 48

Many pre-telescopic naked-eye observations of large sunspot displays exist in the historical records. The most famous of these observations come from China, Japan, Korea, and Greece, but other cultures have made them as well. Pictorial evidence on dated monuments suggests that naked-eye sunspot displays may have been recorded in Mesoamerica as well. In this regard, Yaxchilan Lintel 48 is of particular interest. After a century long gap in naked-eye sunspot observations from Asia, an outstanding cluster of events began in 499 AD and terminated on April 7, 513. Within 5 years of this latter date, Joy b'alam (Knot-eye Jaguar I) was captured and, following an interregnum, K'inich Tatb'u (Skull II; Knot-eye's brother) ascended the throne in 526. In retrospect, Mayan priests might have associated the sunspot displays with the change in political power, and recorded their observations on historical Lintel 48, dated to 526 AD, by the device of a spotted Sun God.

Solar ALMA Observations: Constraining the Chromosphere above Sunspots

Abstract We present the first high-resolution Atacama Large Millimeter/Submillimeter Array (ALMA) observations of a sunspot at wavelengths of 1.3 and 3 mm, obtained during the solar ALMA Science Verification campaign in 2015, and compare them with the predictions of semi-empirical sunspot umbral/penumbral atmosphere models. For the first time, millimeter observations of sunspots have resolved umbral/penumbral brightness structure at the chromospheric heights, where the emission at these wavelengths is formed. We find that the sunspot umbra exhibits a radically different appearance at 1.3 and 3 mm, whereas the penumbral brightness structure is similar at the two wavelengths. The inner part of the umbra is ∼600 K brighter than the surrounding quiet Sun (QS) at 3 mm and is ∼700 K cooler than the QS at 1.3 mm, being the coolest part of sunspot at this wavelength. On average, the brightness of the penumbra at 3 mm is comparable to the QS brightness, while at 1.3 mm it is ∼1000 K brighter than the QS. Penumbral brightness increases toward the outer boundary in both ALMA bands. Among the tested umbral models, that of Severino et al. provides the best fit to the observational data, including both the ALMA data analyzed in this study and data from earlier works. No penumbral model among those considered here gives a satisfactory fit to the currently available measurements. ALMA observations at multiple millimeter wavelengths can be used for testing existing sunspot models, and serve as an important input to constrain new empirical models.

Records of sunspots and aurora candidates in the Chinese official histories of the Yuán and Míng dynasties during 1261–1644

Abstract Records of observations of sunspots and auroras in pre-telescopic historical documents provide useful information about past solar activity both in long-term trends and short-term space weather events. In this study, we present the results of a comprehensive survey of the records of sunspots and aurora candidates in the Yuánshĭ and Míngshĭ, Chinese Official Histories spanning 1261–1368 and 1368–1644, based on continuous observations with well-formatted reportds conducted by contemporary professional astronomers. We then provide a brief comparison of these data with Total Solar Irradiance (TSI) as an indicator of the solar activity during the corresponding periods to show significant active phases between the 1350s–80s and 1610s–30s. We then compared the former with contemporary Russian reports concerning naked-eye sunspots and the latter with contemporary sunspot drawings based on Western telescopic observations. Especially some of the latter are consistent with nitrate signals preserved in ice cores. These results show us some insights on and beyond minima and maxima of solar activity during the 13th–17th centuries.

Corrigendum to “Using Sidereal Rotation Period Expressions to Calculate the Sun’s Rotation Period through Observation of Sunspots”

Corrigendum to “Using Sidereal Rotation Period Expressions to Calculate the Sun’s Rotation Period through Observation of Sunspots”

Evolution of the Sun’s non-axisymmetric toroidal field

Aims. We aim to infer the sub-surface distribution of the Sun's non-axisymmetric azimuthal magnetic flux from observable quantities, such as the surface magnetic field and the large scale plasma flows. Methods. We have built a kinematic flux transport model of the solar dynamo based on the Babcock-Leighton framework. We constructed the source term for the poloidal field using SOLIS magnetograms spanning three solar cycles. Based on this source we calculated the azimuthal flux below the surface. The flux transport model has two free parameters which we constrain using sunspot observations from cycle 22. We compared the model results with observations from cycle 23. Results. The structure of the azimuthal field is mainly axisymmetric. The departures from axisymmetry represent, on average, ~3% of the total azimuthal flux. Owing to its relative weakness, the non-axisymmetric structure of the azimuthal field does not have a significant impact on the location in which the emergences appear or on the amount of flux contained in them. We find that the probability of emergence is a function of the ratio between the flux content of an active region and the underlying azimuthal flux.

Kodaikanal digitized white-light data archive (1921–2011): Analysis of various solar cycle features

Long-term sunspot observations are key to understand and predict the solar activities and its effects on the space weather.Consistent observations which are crucial for long-term variations studies,are generally not available due to upgradation/modifications of observatories over the course of time. We present the data for a period of 90 years acquired from persistent observation at the Kodaikanal observatory in India. We use an advanced semi-automated algorithm to detect the sunspots form each calibrated white-light image. Area, longitude and latitude of each of the detected sunspots are derived. Implementation of a semi-automated method is very necessary in such studies as it minimizes the human bias in the detection procedure. Daily, monthly and yearly sunspot area variations obtained from the Kodaikanal, compared well with the Greenwich sunspot area data. We find an exponentially decaying distribution for the individual sunspot area for each of the solar cycles. Analyzing the histograms of the latitudinal distribution of the detected sunspots, we find Gaussian distributions, in both the hemispheres, with the centers at $\sim$15$^{\circ}$ latitude. The height of the Gaussian distributions are different for the two hemispheres for a particular cycle. Using our data, we show clear presence of Waldmeier effect which correlates the rise time with the cycle amplitude. Using the wavelet analysis, we explored different periodicities of different time scales present in the sunspot area times series.

Non-parametric Data Analysis of Low-latitude Auroras and Naked-eye Sunspots in the Medieval Epoch

We have studied solar activity by analyzing naked-eye sunspot observations and aurorae borealis observed at latitudes below \(45^{\circ}\). We focused on the medieval epoch by considering the non-telescopic observations of sunspots from AD 974 to 1278 and aurorae borealis from AD 965 to 1273 that are reported in several Far East historical sources, primarily in China and Korea. After setting selection rules, we analyzed the distribution of these individual events following the months of the Gregorian calendar. In December, an unusual peak is observed with data recorded in both China and Japan, but not within Korean data.

Records of sunspot and aurora activity during 581–959 CE in Chinese official histories concerning the periods of Suí, Táng, and the Five Dynasties and Ten Kingdoms

Abstract Recent studies concerning radioisotopes in tree rings or ice cores suggest that extreme space weather events occurred during the pre-telescope age. Observational records of naked-eye sunspots and low-latitude auroras in historical documents during this age can provide useful information about past solar activity. In this paper, we present the results of a comprehensive survey of records of sunspots and auroras in Chinese official histories from the 6th century to the 10th century, in the period of Suí, Táng, the Five Dynasties and Ten Kingdoms. These official histories contain records of continuous observations with well-formatted reports conducted under the policy of the governments. A brief comparison of the frequency of observations of sunspots and auroras based on observations of radioisotopes as an indicator of solar activity during the corresponding periods is provided. Using our data, we surveyed and compiled the records of sunspots and auroras in historical documents from various locations and in several languages, and ultimately provide these as open data to the scientific community.

太陽の黒点観測 : 太陽の自転周期を求める( 北海道支部)

太陽の黒点観測 : 太陽の自転周期を求める( 北海道支部)

The relationship between the 5-min oscillation and 3-min oscillations at the umbral/penumbral sunspot boundary

Observations of the main sunspot of AR 11692 were carried out with the 1 m New Vacuum Solar Telescope (NVST) located on the Fuxian Solar Observatory (FSO) in \(H\alpha\) on March 13, 2013. The high cadence (up to 12 s) \(H\alpha\) intensity images help us to investigate the relationship between the 5-min oscillation and 3-min oscillation. It is found that running waves, periodically formed at the wave sources within umbra, propagate outward with the shape of partial arcs. The running waves run across the umbra–penumbra boundary and eventually disappear at the edge of penumbra. But there are obvious differences when we measure the period of running waves in different regions of a sunspot. The period is about 150 s when the running waves are located in umbra, which is a typical 3-min oscillation, and the period is about 300 s when the running waves are located in the penumbra, which is a typical 5-min oscillation. On the basis of time-slice images, we conclude that the waves form in the umbral region with the 5-min oscillation period, which can cause the brightness periodicity change in the umbra region with the 3-min period (in fact, is half of 5-min oscillation) and 5-min in the penumbra.

Global solar wind variations over the last four centuries

The most recent “grand minimum” of solar activity, the Maunder minimum (MM, 1650–1710), is of great interest both for understanding the solar dynamo and providing insight into possible future heliospheric conditions. Here, we use nearly 30 years of output from a data-constrained magnetohydrodynamic model of the solar corona to calibrate heliospheric reconstructions based solely on sunspot observations. Using these empirical relations, we produce the first quantitative estimate of global solar wind variations over the last 400 years. Relative to the modern era, the MM shows a factor 2 reduction in near-Earth heliospheric magnetic field strength and solar wind speed, and up to a factor 4 increase in solar wind Mach number. Thus solar wind energy input into the Earth’s magnetosphere was reduced, resulting in a more Jupiter-like system, in agreement with the dearth of auroral reports from the time. The global heliosphere was both smaller and more symmetric under MM conditions, which has implications for the interpretation of cosmogenic radionuclide data and resulting total solar irradiance estimates during grand minima.