arXiv subjects

Hisashi Hayakawa

Publications and source records attributed to Hisashi Hayakawa.

At least 55 records · Page 3Linked to original sources

arXiv2019

A Transit of Venus Possibly Misinterpreted as an Unaided-Eye Sunspot Observation in China on 9 December 1874

Large sunspots can be observed with the unaided eye under suitable atmospheric seeing conditions. Such observations are of particular value because the frequency of their appearance provides an approximate indication of the prevailing level of solar activity. Unaided-eye sunspot (UES) observations can be traced back well before the start of telescopic observations of the Sun, especially in the East Asian historical records. It is therefore important to compare more modern, UES observations with the results of telescopic sunspot observations, to gain a better understanding of the nature of the UES records. A previous comparison of Chinese UES records and Greenwich photo-heliographic results between 1874 and 1918 indicated that a few of the UES were apparently not supported by direct photographic evidence of at least one sunspot with a large area. This article reveals that one of the Chinese unaided-eye observations had possibly captured the transit of Venus on 9 December 1874. The Chinese sunspot records on this date are compared with Western sunspot observations on the same day. It is concluded that sunspots on the solar disk were quite small and the transit of Venus was probably misinterpreted as a sunspot by the Chinese local scholars. This case indicates that sunspots or comparable "obscuring" objects with an area as large as 1000 millionths of the solar disk could easily have been seen with the unaided eye under suitable seeing conditions. It also confirms the visibility of sunspots near the solar limb with the unaided eye. This study provides an explanation of the apparent discrepancy between the Chinese UES observation on 9 December 1874 and the Western sunspot observations using telescopes, as well as a basis for further discussion on the negative pairs in 1900 and 1911, apparently without sufficiently large area.

astro-ph.SR↗

arXiv2019

Occurrence of Great Magnetic Storms on 6-8 March 1582

Although knowing the occurrence frequency of severe space weather events is important for a modern society, it is insufficiently known due to the lack of magnetic or sunspot observations, before the Carrington event in 1859 known as one of the largest events during the last two centuries. Here, we show that a severe magnetic storm occurred on 8 March 1582 based on auroral records in East Asia. The equatorward boundary of auroral visibility reached 28.8° magnetic latitude. The equatorward boundary of the auroral oval is estimated to be 33.0° invariant latitude (ILAT), which is comparable to the storms on 25/26 September 1909 (~31.6° ILAT, minimum Dst of -595 nT), 28/29 August 1859 (~36.5° ILAT), and 13/14 March 1989 (~40° ILAT, minimum Dst of -589 nT). Assuming that the equatorward boundary is a proxy for the scale of magnetic storms, we presume that the storm on March 1582 was severe. We also found that the storm on March 1582 lasted, at least, for three days by combining European records. The auroral oval stayed at mid-latitude for the first two days and moved to low-latitude (in East Asia) for the last day. It is plausible that the storm was caused by a series of ICMEs (interplanetary coronal mass ejections). We can reasonably speculate that a first ICME could have cleaned up interplanetary space to make the following ICMEs more geo-effective, as probably occurred in the Carrington and Halloween storms.

astro-ph.SR↗

arXiv2019

Intense geomagnetic storm during Maunder minimum possibly by a quiescent filament eruption

The sun occasionally undergoes the so-called grand minima, in which its magnetic activity, measured by the number of sunspots, is suppressed for decades. The most prominent grand minima, since the beginning of telescopic observations of sunspots, is the Maunder minimum (1645-1715), when the sunspots became rather scarce. The mechanism underlying the grand minima remains poorly understood as there is little observational information of the solar magnetic field at that time. In this study, we examine the records of one candidate aurora display in China and Japan during the Maunder minimum. The presence of auroras in such mid magnetic latitudes indicates the occurrence of great geomagnetic storms that are usually produced by strong solar flares. However, the records of contemporary sunspot observations from Europe suggest that, at least for the likely aurora event, there was no large sunspot that could produce a strong flare. Through simple theoretical arguments, we show that this geomagnetic storm could have been generated by an eruption giant quiescent filament, or a series of such events.

astro-ph.SR↗

arXiv2019

Do the Chinese Astronomical Records Dated AD 776 January 12/13 Describe an Auroral Display or a Lunar Halo? A Critical Re-examination

The enhancement of carbon-14 in tree rings around AD 774/775 has generated wide interest in solar activity at that time. The historical auroral records have been examined critically. Of particular interest was the "white vapour" observed in China on AD 776 January 12/13. Both Usoskin et al. (2013, Astron. Astrophys. 55, L3; U13) and Stephenson (2015, Adv. Sp. Res. 55, 1537; S15) interpreted this record as an auroral display. Subsequently, Neuhäuser and Neuhäuser (2015, Astron. Nachr. 336, 225; NN15) proposed five "criteria" for the likeliness of aurorae and on this basis rejected an auroral interpretation. Instead, they interpreted it as a lunar halo, and suggested there were no auroral records as a proxy of solar activity in the interval AD 774-785. We consider if their "lunar halo hypothesis" and their auroral criteria could be of use in future researches on historical auroral candidates. We first show a counter-example for the lunar halo hypothesis from a parallel record on 1882 November 17, which was seen as a whitish colour, in the southerly direction, and near the Moon. We then consider NN15's criteria on colour, direction, and sky brightness and investigate other counter-examples from early-modern auroral observations. We also consider the extension of the white vapour in AD 776 according to the distribution of Chinese asterisms, and show that its large extension was inconsistent with the lunar halo hypothesis. Conversely, the streaks of white vapour penetrating the eight Chinese asterisms can be reproduced if we consider auroral-ray structures at altitudes between 97 km and 170 km, along geomagnetic field lines between the L-shells L=1.55 and 1.64. Our investigations show that we should consider candidate auroral records in historical documents not on the basis of the newly suggested a priori criteria by NN15 but on all the available observational evidence.

astro-ph.SR↗

arXiv2019

The Celestial Sign in the Anglo-Saxon Chronicle in the 770s: Insights on Contemporary Solar Activity

The anomalous concentration of radiocarbon in 774/775 attracted intense discussion on its origin, including the possible extreme solar event(s) exceeding any events in observational history. Anticipating such extreme solar events, auroral records were also surveyed in historical documents and those including the red celestial sign after sunset in the Anglo-Saxon Chronicle (ASC) were subjected to consideration. Usoskin et al. (2013: U13) interpreted this record as an aurora and suggested enhanced solar activity around 774/775. Conversely, Neuhauser and Neuhauser (2015a, 2015b: N15a and N15b) interpreted "after sunset" as during sunset or twilight; they considered this sign as a halo display and suggested a solar minimum around 774. However, so far these records have not been discussed in comparison with eyewitness auroral records during the known extreme space-weather events, although they were discussed in relationship with potential extreme events in 774/775. Therefore, we reconstruct the observational details based on the original records in the ASC and philological references, compare them with eyewitness auroral observations during known extreme space-weather events, and consider contemporary solar activity. We clarify the observation was indeed "after sunset", reject the solar halo hypothesis, define the observational time span between 25 Mar. 775 and 25 Dec. 777, and note the parallel halo drawing in 806 in the ASC shown in N15b was not based on the original observation in England. We show examples of eyewitness auroral observations during twilight in known space-weather events, and this celestial sign does not contradict the observational evidence. Accordingly, we consider this event happened after the onset of the event in 774/775, but shows relatively enhanced solar activity, with other historical auroral records in the mid-770s, as also confirmed by the Be data from ice cores.

astro-ph.SR↗

arXiv2019

Revisiting Kunitomo's Sunspot Drawings during 1835-1836 in Japan

We revisit the sunspot drawings made by the Japanese astronomer Kunitomo Toubei during 1835-1836 and recount the sunspot group number for each image. There are two series of drawings, preliminary (P, containing 17 days with observations) and summary (S, covering 156 days with observations), all made using brush and ink. S is a compilation of drawings for the period from February 1835, to March 1836. Presently, the P drawings are available only for one month, September 1835; those of other periods have presumably been lost. Another drawing (I) lets us recover the raw group count (RGC) for 25 September 1836, on which the RGC has not been registered in the existing catalogs. We also revise the RGCs from P and S using the Zurich classification and determine that Kunitomo's results tend to yield smaller RGCs than those of other contemporary observers. In addition, we find that Kunitomo's RGCs and spot areas have a correlation (0.71) that is not very different from the contemporary observer Schwabe (0.82). Although Kunitomo's spot areas are much larger than those determined by Schwabe due to skill and instrument limitations, Kunitomo at least captured the growing trend of the spot activity in the early phase of the Solar Cycle 8. We also determine the solar rotation axis to estimate the accurate position (latitude and longitude) of the sunspot groups in Kunitomo's drawings.

astro-ph.SR↗

arXiv2018

Lifetimes and Emergence/Decay Rates of Star Spots on Solar-type Stars Estimated by Kepler Data in Comparison with Those of Sunspots

Active solar-type stars show large quasi-periodic brightness variations caused by stellar rotations with star spots, and the amplitude changes as the spots emerge and decay. The Kepler data are suitable for investigations on the emergence and decay processes of star spots, which are important to understand underlying stellar dynamo and stellar flares. In this study, we measured temporal evolutions of star spot area with Kepler data by tracing local minima of the light curves. In this analysis, we extracted temporal evolutions of star spots showing clear emergence and decay without being disturbed by stellar differential rotations. We applied this method to 5356 active solar-type stars observed by Kepler and obtained temporal evolutions of 56 individual star spots. We calculated lifetimes, emergence and decay rates of the star spots from the obtained temporal evolutions of spot area. As a result, we found that lifetimes ($T$) of star spots are ranging from 10 to 350 days when spot areas ($A$) are 0.1-2.3 percent of the solar hemisphere. We also compared them with sunspot lifetimes, and found that the lifetimes of star spots are much shorter than those extrapolated from an empirical relation of sunspots ($T\propto A$), while being consistent with other researches on star spot lifetimes. The emerging and decay rates of star spots are typically $5 \times 10^{20}$ $\rm Mx\cdot h^{-1}$ ($8$ $\rm MSH\cdot h^{-1}$) with the area of 0.1-2.3 percent of the solar hemisphere and are mostly consistent with those expected from sunspots, which may indicate the same underlying processes.

astro-ph.SR↗

arXiv2018

Low-Latitude Aurorae during the Extreme Space Weather Events in 1859

The Carrington storm (September 1/2, 1859) is one of the largest magnetic storms ever observed and it has caused global auroral displays in low-latitude areas, together with a series of multiple magnetic storms during August 28 and September 4, 1859. In this study, we revisit contemporary auroral observation records to extract information on their elevation angle, color, and direction to investigate this stormy interval in detail. We first examine their equatorward boundary of "auroral emission with multiple colors" based on descriptions of elevation angle and color. We find that their locations were 36.5 deg ILAT on August 28/29 and 32.7 deg ILAT on September 1/2, suggesting that trapped electrons moved to, at least, L~1.55 and L~1.41, respectively. The equatorward boundary of "purely red emission" was likely located at 30.8 deg ILAT on September 1/2. If "purely red emission" was a stable auroral red arc, it would suggest that trapped protons moved to, at least, L~1.36. This reconstruction with observed auroral emission regions provides conservative estimations of magnetic storm intensities. We compare the auroral records with magnetic observations. We confirm that multiple magnetic storms occurred during this stormy interval, and that the equatorward expansion of the auroral oval is consistent with the timing of magnetic disturbances. It is possible that the August 28/29 interplanetary coronal mass ejections (ICMEs) cleared out the interplanetary medium, making the ICMEs for the Carrington storm on September 1/2 more geoeffective.

physics.space-ph↗

arXiv2018

Sporadic Aurora near Geomagnetic Equator: In the Philippines, on 27 October 1856

While low latitude auroral displays are normally considered to be a manifestation of magnetic storms of considerable size, Silverman (2003, JGR, 108, A4) reported numerous "sporadic auroras" which appear locally at relatively low magnetic latitudes during times of just moderate magnetic activity. Here, a case study is presented of an aurora near the geomagnetic equator based on a report from the Philippine Islands on 27 October 1856. An analysis of this report shows it to be consistent with the known cases of sporadic aurorae except for its considerably low magnetic latitude. The record also suggests that extremely low-latitude aurora is not always accompanied with large magnetic storms. The description of its brief appearance leads to a possible physical explanation based on an ephemeral magnetospheric disturbance provoking this sporadic aurora.

physics.space-ph↗

arXiv2018

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.

astro-ph.SR↗

arXiv2018

The Great Space Weather Event during February 1872 Recorded in East Asia

The study of historical great geomagnetic storms is crucial for assessing the possible risks to the technological infrastructure of a modern society, caused by extreme space-weather events. The normal benchmark has been the great geomagnetic storm of September 1859, the so-called "Carrington Event". However, there are numerous records of another great geomagnetic storm in February 1872. This storm, about 12 years after the Carrington Event, resulted in comparable magnetic disturbances and auroral displays over large areas of the Earth. We have revisited this great geomagnetic storm in terms of the auroral and sunspot records in the historical documents from East Asia. In particular, we have surveyed the auroral records from East Asia and estimated the equatorward boundary of the auroral oval to be near 24.3 deg invariant latitude (ILAT), on the basis that the aurora was seen near the zenith at Shanghai (20 deg magnetic latitude, MLAT). These results confirm that this geomagnetic storm of February 1872 was as extreme as the Carrington Event, at least in terms of the equatorward motion of the auroral oval. Indeed, our results support the interpretation of the simultaneous auroral observations made at Bombay (10 deg MLAT). The East Asian auroral records have indicated extreme brightness, suggesting unusual precipitation of high-intensity, low-energy electrons during this geomagnetic storm. We have compared the duration of the East Asian auroral displays with magnetic observations in Bombay and found that the auroral displays occurred in the initial phase, main phase, and early recovery phase of the magnetic storm.

physics.space-ph↗

arXiv2018

Sunspot Drawings by Japanese Official Astronomers in 1749-1750

Sunspot observations with telescopes in 18th century were carried out in Japan as well. 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 analyze manuscripts of this account to show in total 15 sunspot drawings in 1749-1750. These observations were carried out by contemporary official astronomers in Japan, with telescopes covered by zongurasus (< zonglas in Dutch, corresponding to "sunglass" in English). We count their group number of sunspots to locate them in long-term solar activity and show that their observations were situated around the solar maximum in 1749 or 1750. We also computed their locations and areas, while we have to admit the difference of 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 improve the known sunspot indices.

physics.hist-ph↗

arXiv2017

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.

astro-ph.SR↗

arXiv2017

Long-Lasting Extreme Magnetic Storm Activities in 1770 Found in Historical Documents

Dim red aurora at low magnetic latitudes is a visual and recognized manifestation of geomagnetic storms. The great low-latitude auroral displays seen throughout East Asia on 16-18 September 1770 are considered to manifest one of the greatest storms. Recently found 111 historical documents in East Asia attest that these low-latitude auroral displays were succeeding for almost 9 nights during 10-19 September 1770 in the lowest magnetic latitude areas (< 30°). This suggests that the duration of the great magnetic storm is much longer than usual. Sunspot drawings from 1770 reveals the fact that sunspots area was twice as large as those observed in another great storm of 1859, which substantiates this unusual storm activities in 1770. These spots likely ejected several huge, sequential magnetic structures in short duration into interplanetary space, resulting in spectacular world-wide aurorae in mid-September 1770. These findings provide new insights about the history, duration, and effects of extreme magnetic storms that may be valuable for those who need to mitigate against extreme events.

astro-ph.SR↗

arXiv2017

Records of Auroral Candidates and Sunspots in Rikkokushi, Chronicles of Ancient Japan from Early 7th Century to 887

In this article, we present the results of the surveys on sunspots and auroral candidates in Rikkokushi, Japanese Official Histories from the early 7th century to 887 to review the solar and auroral activities. In total, we found one sunspot record and 13 auroral candidates in Rikkokushi. We then examine the records of the sunspots and auroral candidates, compare the auroral candidates with the lunar phase to estimate the reliability of the auroral candidates, and compare the records of the sunspots and auroral candidates with the contemporary total solar irradiance reconstructed from radioisotope data. We also identify the locations of the observational sites to review possible equatorward expansion of auroral oval. These discussions suggest a major gap of auroral candidates from the late 7th to early 9th century, which includes the minimum number of candidates reconstructed from the radioisotope data, a similar tendency as the distributions of sunspot records in contemporary China, and a relatively high magnetic latitude with a higher potential for observing aurorae more frequently than at present.

astro-ph.SR↗

arXiv2017

Records of Sunspots and Aurora Candidates in the Chinese Official Histories of the Yuán and Míng Dynasties during 1261-1644

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 Yuánshǐ and Míngshǐ, 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 1350s-80s and 1610s-30s. We then compared the former with contemporary Russian reports for 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 not only minima and maxima of solar activity during 13th - 17th century.

astro-ph.SR↗

arXiv2016

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

Recent studies of radioisotopes in tree rings or ice cores suggest that extreme space weather events occurred in the pre-telescope age. Observational records of naked-eye sunspots and low-latitude auroras in historical documents in pre-telescopic age can provide useful information on 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 government. A brief comparison of the frequency of observations of sunspots and auroras with the observations of radioisotopes as an indicator of solar activity during the corresponding periods is provided. Based on our data, we survey and compile the records of sunspots and auroras in historical documents from variouslocations and in several languages, and ultimately provide these as open data to the scientific community.

physics.hist-ph↗

arXiv2016

Historical Auroras in the 990s: Evidence for Great Magnetic Storms

Recently, a significant carbon-14 enhancement in the year 994 in tree rings has been found, suggesting an extremely large cosmic ray flux event during a short period. The origin of this particular cosmic ray event has not been confirmed, but one possibility is that it is of solar origin. Contemporary historical records of low latitude auroras can be used as supporting evidence for intense solar activity around that time. We investigated the previously reported as well as the new records found in contemporary observations from the 990s to determine potential auroras. Records of potential red auroras in the late 992 and early 993 were found around the world, i.e. in the Korean Peninsula, Germany, and the Island of Ireland, suggesting the occurrence of an intense geomagnetic storm driven by solar activity.

astro-ph.SR↗