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COMMENTARY Ms. Hisako Koyama: From Amateur 10.1002/2017SW001704 to Long-Term Solar Observer Key Points: Delores Knipp1,2 , Huixin Liu3 , and Hisashi Hayakawa4,5 • Ms. Hisako Koyama was a dedicated solar observer, and a long-serving staff 1Smead Aerospace Engineering Sciences Department, University of Colorado Boulder, Boulder, CO, USA, 2High Altitude member of the National Museum of 3 Nature and Science, Tokyo , National Center for Atmospheric , Boulder, CO, USA, Department of Earth and Planetary Science, 4 • She created a multidecadal record of Faculty of Science, Kyushu University, Fukuoka, Japan, Graduate School of Letters, Osaka University, Toyonaka, Japan, that serves as a backbone of 5Japan Society for the Promotion of Science, Tokyo, Japan the recent number recalibration • We tell her little-known story so that Abstract The path to science for a girl of any nationality born in the early twentieth century was her contributions to science may be known formidable-to-nonexistent. Yet paths were forged by a few. We present the little-known story of one of Japan’s premier solar observers and her contribution to the world’s understanding of sunspots and space weather cycles. Ms. Hisako Koyama, born in Tokyo in 1916, became a passionate amateur astronomer, a dedicated solar observer, and a long-serving staff member of the National Museum of Nature and Science, Correspondence to: D. Knipp, Tokyo. As a writer for amateur journals she advised many on the details and joys of viewing. [email protected] She created a consistent, extended record of sunspots. Her multidecade archive of sunspot drawings is one of the “backbones” for the recent international recalibration of the sunspot record that provides insight into Citation: space weather reaching back to the early 1600s. We detail her contributions to the citizens of Japan as an Knipp, D., Liu, H., & Hayakawa, H. (2017). ambassador of astronomy and her international contribution to understanding the symmetries and Ms. Hisako Koyama: From amateur asymmetries of the solar cycle. We comment on the value of her continuous record of sunspots and on her astronomer to long-term solar observer. Space Weather, 15, 1215–1221. https:// tenacity in promoting a science that links to space weather. doi.org/10.1002/2017SW001704

Received 6 AUG 2017 1. Introduction—A Passion for Observing Accepted 9 SEP 2017 Accepted article online 27 SEP 2017 There are some in this world who will find their way to science no matter what the impediments. Ms. Hisako Published online 2 OCT 2017 Koyama was such an individual. With some encouragement and mostly on-the-job training, she created a multidecadal sunspot record that is a masterpiece of consistent sunspot . In Japan she was an ambassador for astronomy, writing numerous short articles in regional and national Japanese astronomy bul- letins. Born into 1916 urban Japanese society, she graduated from a Tokyo high-school for girls in the 1930s. In so doing she achieved at that time a level of education of which many girls could only dream. Ms. Koyama was fascinated with objects beyond Earth’s atmosphere. An account in the pictorial magazine, Asahigraph (1951), reports that she was intrigued by a “shooting ,” and had read two or three astronomy books, including a “red book” (reference) guide to making (Kibe, 1936) prior to beginning her observational career in the early 1940s. Her comments in an article for Japan’s Oriental Astronomical Association (OAA) indicate that after visiting the Tonichi at Yuraku-cho in Tokyo (Koyama, 1971), she assembled a and polished the lens with the help of a telescope shopkeeper (Koyama, 1972). Referring to World War II, Renshaw and Ihara (1997) noted that “During city-wide air-raid blackouts, Hisako Koyama would drag her futon into the yard and hide under it, lighting her variable-star charts with a small flashlight.” In her own words, Ms. Koyama reported that “I made my first step towards astronomy by star watching with the astronomical chart in hand.” Her interest in the heavens grew during the spring of 1944 as she began making sunspot observations with a 36 mm X 60 refractor telescope, which was a gift from her father. According to her article for the fiftieth anniversary of the OAA, as a young woman Ms. Koyama wanted to join OAA’s section in 1944; however, finding that her 36 mm telescope was insufficient for lunar observing, she turned to the Solar section (Koyama, 1971). After 1 month of trying during solar minimum period, she managed to get her first sunspot sketch and gathered enough courage to send it to the then OAA Solar section pre- sident, Professor Issei Yamamoto. Then, after receiving an encouraging reply from Yamamoto, written, “Thank you for your report. Yes, they are sunspots,” she began what can best be described

©2017. American Geophysical Union. as an extraordinary career dedicated to amateur astronomical observations and professional solar observa- All Rights Reserved. tions (Koyama, 1971).

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Figure 1. (a) Ms. Koyama with the 20 cm telescope in 1951 (courtesy of Asahigraph); (b) a full view of the Nikon 20 cm telescope with Ms. Koyama inset reproduced from Koyama (1985).

Through 1945 she developed her skills for sketching sunspots via “attenuated direct-viewing” under the guidance of Professor Yamamoto (Horaguchi & Nakajima, 2001). In May 1946 Ms. Koyama, by then a war widow, began making semiregular solar observations via projection with a Nikon 20 cm refractor telescope at the Tokyo Science Museum (henceforth referred to by its current name: National Museum of Nature and Science, NMNS) with the supervision of Mr. Sadao Murayama, Chief Astronomer. The image from the telescope, which was in use between 1931 and 2005, was projected to a sheet of paper as a 30 cm image where Ms. Koyama detailed the visible solar features and added notations related to impor- tant features, observing (seeing) conditions, and time. Ms. Koyama quickly made a transition from amateur to staff observer. She attended the first meeting of the Japan Society for Astronomical Studies in November 1945 and was introduced by Mr. Otani, her predecessor at NMNS (Shigehisa, 1995). From 1946 onward Ms. Koyama was a staff member of the NMNS where she observed with the same 20 cm refractor telescope (Figures 1a and 1b) through her official retirement in 1981, and for an additional 10 years as a Fellow of the Museum. According to O’Meara (1987) and Fujimori (1994), she posted monthly reports to several astronomical institutions including the Swiss Federal Observatory in Zurich and the Royal Observatory of Belgium. Through 1984 she located and categorized more than 8,000 sunspot groups, which were published in her monograph entitled, “Observations of Sunspots 1947–1984,” (Koyama, 1985). Over her lifetime she made more than 10,000 solar sketches (Horaguchi & Nakajima, 2001).

2. Staff Years at the Museum: Public Work and Career 2.1. Outreach In addition to making her precision solar drawings, Ms. Koyama was deeply involved in “outreach” and planetary and variable-star viewing. Some photographs show her surrounded by children or the viewing public at various . Ms. Koyama was often the public face of astronomy to museum visitors as she explained astronomical phenomena and demonstrated equipment. Sometimes her public interaction occurred many times a day, especially on Saturdays and holidays. She organized special events and observa- tional campaigns for eclipses. Close approaches of nearby , or planetary conjunctions, brought many extra visitors and contact time. Saturday nights were frequently dedicated to watch events (Fujimori, 1997; Sato, 1997). Ms. Koyama also supported a monthly seminar on star constellations (Koyama, 1981). She wrote short columns and articles related to telescopes, astronomy, and the and made yearly reports to the Astronomical Herald published by the Astronomical Society of Japan between 1967 and 1989.

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(Fujimori, 1994). In her published account of the 21 July 1963 she described the observation campaign at Bihiro organized by the NMNS, in which about 40 amateur and 700 members of the public from all over Japan participated. Between the gaps of “many coming and going clouds,” they could observe the “inner corona, prominence, and the diamond ring” (Koyama, 1963).

2.2. Sun Drawings, Special Observations, and Published Works Ms. Koyama lived within walking distance of the NMNS where she worked a busy schedule of outreach and observing alongside her boss, Chief Astronomer Sadao Murayama. She recounted her efforts in a 1981 memoir that documented 35 years with the Museum (Koyama, 1981). Her observation time was planned for twice a day, in about 1 h intervals. Sunspots were year-round phenomena requiring drawings in frigid winter and sweltering summer, all the while dealing with cloudiness characteristic of coastal Japan. Frequently, nature did not cooperate. Ms. Koyama noted that the worst condition “is not rain, but a day with clouds frequently coming and going!” She joked that she could “probably win a competition for endurance, if there were one” (Koyama, 1981). Sunspots and their groupings were Ms. Koyama’s vocation and avocation. Early in her career she published a description of how to count sunspots (Koyama, 1949). Subsequently, she described the methods of counting sunspots in several of her articles (e.g., Koyama, 1965) and emphasized the importance of being consistent in one’s own counting standard, citing discussions with Professor Max Waldmeier, Director of the Swiss Federal Observatory in Zurich, Switzerland, who visited her at the NMNS in September 1963 (Koyama, 1965). In her 1965 article, she compared different methods and commented that counting only the umbra would make the least error in the long run. Based on this, she clearly recommended beginners to use this method “without hesitation.” In early April 1947, she sketched the largest sunspot of the twentieth century (Figure 2a, 5 April 1947). The spot in the Sun’s southern hemisphere ultimately reached a maximum area of 6,132 millionths of the dayside sector (Newton, 1955). Several years later she witnessed the white-light flare of 15 November 1960 while she was sketching sunspots. Figure 2b shows her drawing and the times of the white-light flares. Her annotation includes the following: “I witnessed the (projection of the) white light flare by my naked eyes.” As a coauthor on the manuscript describing the event, Ms. Koyama noted that “part of the large sunspot of type F suddenly brightened in pearly white colour at 02h21m, and again at 02h23m.5 at an adjacent part. The durations were both less than two minutes” (Nagasawa et al., 1961). Ms. Koyama was keenly aware of the history and importance of the sunspot butterfly diagram—a diagram that shows the latitudinal positions of sunspots or groups for each solar rotation over time. She commented on the related data sets available from Carrington, Spörer, Maunder, Menzel, and Abetti (Koyama, 1964). In the article, she showed her own 17 year version of the sunspot butterfly diagram, reflecting that “17 years (of observation) is not enough to make even 2 butterflies!” Her observational persistence paid off, ultimately producing three and a half sunspot butterflies (see Figure 2c). According to O’Meara (1987), Ms. Koyama’s sunspot records were unique in that “They are made individually for the northern and southern halves of the disk, and for a circular zone at the Sun’s center.” The international solar community strongly urged Ms. Koyama to publish her results. She responded by tabulating the northern hemisphere, southern hemisphere, and total relative sunspot numbers (SSN) in a 354-page book that includes her version of a sunspot-group butterfly diagram (Koyama, 1985). The diagram shows each of her observed sunspot groups (equivalently active regions, which are tangled nests of solar magnetism that give rise to most solar eruptions). It is worth noting the Ms. Koyama’s sunspot-group butterfly record is slightly longer than the original butterfly record from Annie and Walter Maunder, which was sent to the United States for safekeeping just before World War II (see the Maunder butterfly image in Dalla & Fletcher (2016), or at https://www2.hao.ucar.edu/news/ 2016-sep/pioneer-solar-astronomy). Figure 2d shows the number of Ms. Koyama’s observing days based on data from Horaguchi and Nakajima (2001). Though making a remarkably long record of sunspots, Ms. Koyama was extremely modest and often ended her articles with comments like “It is just 3 solar cycles…only a blink for the Sun, … I wish I can leave as many as possible (SSN) records which can be used as references for people to come” (Koyama, 1981). She created such a record in her published data book (Koyama, 1985).

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Figure 2. (a) Full disk sunspot drawing on 5 April 1947; (b) close-up of sunspot group with notation of the white light flare times on 15 November 1960. Note that refractor telescopes produce images that are inverted from left to right; thus, the Sun’s west limb is on the left in these images. Both images are courtesy of the National Museum of Nature and Science, Tokyo (2017) and available at the database of Observations of Sunspots 1947–1996, Hisako KOYAMA (http://www.kahaku.go. jp/research/db/science_engineering/sunspot) last accessed on 4 August 2017; (c) sunspot-group butterfly diagram, solar latitude À50° to +50° (vertical axis), time in years (horizontal axis) reproduced from Koyama (1985); (d) number of observing days 1947–1984.

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2.3. Recognition and Long-Term Influence Ms. Hisako Koyama was held in high regard by fellow observers. Mr. Takeshi Sato, past Director of the Jupiter- Saturn Section of OAA, wrote in a 1972 postconference summary about the local organizers of Japanese Jupiter Observers’ Conference: “Miss Hisako Koyama of the museum staff kindly served tea and cakes. She is a sunspot observer of great renown” (Sato, 1972). In1986 she was awarded the OAA Prize of Encouragement of Academic Research, given in honor of Professor Issei Yamamoto (Fujimori, 1994). She was also recognized by fellow OAA member, S. Nakano, who proposed that International Astronomical Union Minor 1951AB be renamed 3383 Koyama (Schmadel, 2012). The citation reads: “Named in honor of Hisako Koyama, staff member of the National Science Museum in Tokyo for more than 40 years, interna- tionally known for her solar observations….” Ms. Koyama’s wish for a legacy for her records has been realized. Yallop (1985) wrote, “Her observations are now preserved for posterity in a book which is excellently produced, and there should be a copy in all main astronomical libraries.” More recently, her 50 year sunspot record was highlighted in the Japanese version of National Geographic (Omura, 2004) in an article subtitled “Hisako Koyama, who left more than 10000 detailed sketches.” A web search reveals that her 1985 data book has been referenced in more than 20 scientific articles and in various guides, compendia, and conference proceedings (e.g., Kubota, 1985; Temmer et al., 2002, 2006). Further, the Koyama sunspot drawings have been digitized into an important and freely avail- able collection at NMNS (Horaguchi & Nakajima, 2001). (See http://www.kahaku.go.jp/research/db/science_ engineering/sunspot/, which provides an extension of the work published in Koyama, 1985.) A tabulation of her daily summed sunspot group numbers can be found within https://www.ngdc.noaa.gov/stp/space- weather/solar-data/solar-indices/sunspot-numbers/group/group-sunspot-numbers_standard-deviation_ daily-values(dailysd)_depricate.txt. Discussing Ms. Koyoma’s data record, Swinson et al. (1986) noted that “These data are particularly valuable because the 37-yr span of data were provided by the same observer (Hisako Koyama) using the same tele- scope and the same method of observation.” Swinson et al. (1986) used the “particularly long and coherent data set” from the Koyama record combined with other related data to examine the north-south asymmetry in solar activity over many solar cycles. Swinson et al. (1991) further investigated the significance of such asymmetries as they relate to density gradients. One of the implications of the asymmetry is an inner-heliospheric density gradient in cosmic ray intensity normal to the ecliptic plane, which can modulate the cosmic ray diurnal variation amplitude at Earth. Ms. Koyama’s records have contributed to the fabric of solar asymmetries studies recently reviewed in Wang and Robbrecht (2011) and Wang (2014). In a recent effort Clette et al. (2014), Svalgaard and Schatten (2016), and Vaquero et al. (2016) reconstructed the sunspot group count from 1610s to the early 2000s by a reassessing original sources. The reconstruction involved a “backboning” technique that designates “a primary observer for a certain (long) interval and normalize(s) all other observers individually to the primary based on overlap with only the primary….” The primary observer should have a long observational series and high-quality observations related to “…regu- larity of observing, suitable telescope, and lack of obvious problems,” (Svalgaard & Schatten, 2016). Ms. Koyama’s record serves as one of the official backbones for the 400 year recalibration effort. Figures 14 and 15 of Svalgaard and Schatten (2016) document the results. Vaquero et al. (2016) note that “… the sunspot drawings by Galileo, Gassendi, Staudach, Schwabe, Wolf (small telescope), and Koyama were analyzed in order to obtain the number of sunspot groups using modern criteria based on the morphological classification of sunspot groups.” Clearly, Ms. Koyama’s sunspot records are in a class of great historical scientific records.

3. Commentary In this article, we highlight the significant contribution of a Japanese woman observer to space weather, solar science, and astronomy. Early on, Ms. Koyama had a fundamental grasp of importance of consistency in observations (Koyama, 1965). Observational skills, persistence, consistency, and a keen eye for solar behavior have earned her a place in history. How fortunate we are that Ms. Koyama’s colleagues pushed her to publish her data. From her 1985 data book we know the location of sunspot groups that supported solar active regions—the most likely solar sources of space weather from 1947 to 1984. These can be compared forward and backward in time with data from other whose records span the post-World War II era and

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the space age. We also have from Ms. Koyama, the continuity of record that shows the Sun’s northern hemi- sphere has been more active than the southern hemisphere. Importantly, the world also has online access to her remarkable data set. We can hope that other observatories and archiving units will make similar data sets available for space weather study. Ms. Koyama was a most unusual woman of her time. As a scientist, she bridged the amateur and professional world. She preferred “doing” activities: observing, data recording, interacting with the public, and writing. No doubt many Japanese citizens benefited from personal interaction with her. The space and geophysics com- munity continues to benefit from her regular and precise observations of the Sun. Although we know very little of her young personal life other than she was relatively well educated and had a father who supported her desire to view the by providing a telescope, we can see from snippets in Japanese amateur astron- omy articles that she had a passion for observing, as revealed in her 1981 article: “I simply can’t stop obser- ving when thinking that one can never know when the nature will show us something unusual.” It seems that she needed only to get an encouraging message from a professional astronomer to launch a career marked by a passion for observing and devotion to creating a long, consistent record for others to use. How many young “Ms. Koyamas” might there be in today’s world, just on the verge of scientific contribution and discovery, if only for a nudge of encouragement in the right direction? We hope this manuscript describing Ms. Koyama’s work serves as encouragement and inspiration for future scientists.

Acknowledgments References D. J. K. thanks William Denig and Sarah Gibson for commenting on the manu- Asahigraph (1951). Researchers of : We are not professional [in Japanese], 10-3, 18. script. She also thanks Leif Svalgaard for Clette, F., Svalgaard, L., Vaquero, J. M., & Cliver, E. W. (2014). Revisiting the sunspot number: A 400-year perspective on the solar cycle. Space – bringing Ms. Koyama’s record to light. Science Reviews, 16,35 103. https://doi.org/10.1007/s11214-014-0074-2 – H. H. thanks T. Horaguchi, K. Saijo, T. Dalla, S., & Fletcher, L. (2016). A pioneer of solar astronomy. Astronomy and Geophysics, 57(5), 5.21 5.23. https://doi.org/10.1093/astrogeo/atw181 – Nakajima, and K. Noji, and other Fujimori, K. (1994). The Sun: In Morikubo, Shigeru et al. Sequel History for Japanese Amateur Astronomy [in Japanese] (pp. 36 45). Tokyo: Nihon National Museum staff members, fel- Kousei Sha. lows, and Ms. Koyama’s younger collea- Fujimori, K. (1997). Sunspot observer, Koyama Hisako [in Japanese]. The Heavens, 865, 17. gues, for providing access to archived Horaguchi, T., & Nakajima, T. (2001). A database of sunspot observation (1) sketch images. Bulletin of the National Science Museum Ser. E – data, interviews related to Ms. Koyama’s Physical Sciences & Engineering, 24(1 12), 2001. life, and permissions for image repro- Kibe, S. (1936). How to Make Astronomical Telescopes and Observations [in Japanese]. Tokyo: Seibundo. ductions. H. H. also thanks Shibata for Koyama, H. (1949). Sunspot observations [in Japanese]. Astronomy and Meteorology, 15(5), 34. introduction to staff at NMNS. Koyama, H. (1963). Solar eclipse observation in Bihoro [in Japanese]. Astronomical Herald, 56(11), 226. fl H. L. thanks Sawako Maeda for interest- Koyama, H. (1964). Butter y diagram of the Sun by the recent observations [in Japanese]. Astronomical Herald, 57(9), 184. – ing discussions. H. L. acknowledges Koyama, H. (1965). Additional notes on how to count sunspot numbers [in Japanese]. The Heavens, 46(481), 154 155. support from JSPS KAKENHI Koyama, H. (1971). Introduction to the astronomical observation (celebrating the 50th anniversary of OAA) [in Japanese]. The Heavens, – grant 15K05301. H. H. acknowledges 52(548), 3 4. – support form Grant-in-Aid from (1) JSPS Koyama, H. (1972). Telescope and the Red book [in Japanese]. Astronomical Herald, 65(1), 215 216. – Research Fellow JP17J06954; (2) the Koyama, H. (1981). 35 years with the 20 cm telescope [in Japanese]. Natural Science and Museums, 48(3), 111 116. – Ministry of Education, Culture, Sports, Koyama, H. (1985). Observations of Sunspots 1947 1984. Tokyo: Kawade Shobo Shinsha Publishers. – Science and Technology of Japan, Kubota, J. (1985). Book review: Koyama Hisako, observations of sunspots 1947 1984 [in Japanese]. The Heavens, 723, 242. fl grant JP15H05816; and (3) the Nagasawa, S., Takahura, T., Tsuchiya, A., Tanaka, H., & Koyama, H. (1961). A very unusual are on November 15, 1960. Publications of the – Exploratory and Mission Research Astronomical Society of Japan, 13(1), 129 134. – Projects of the Research Institute for National Museum of Nature and Science, Tokyo (2017). Observations of sunspots 1947 1996, Hisako Koyama. [Available at http://www. Sustainable Humanosphere. D. J. K. was kahaku.go.jp/research/db/science_engineering/sunspot/ last accessed on 4 August 2017.] – partially supported by NSF grant Newton, H. W. (1955). The lineage of the great sunspots. Vistas in astronomy, 1, 666 674. https://doi.org/10.1016/0083-6656(55)90081-7 ’ – DES-1446704 via a contract with O Meara, S. J. (1987). Amateur astronomers spotlight on Japan. Sky and Telescope, 73(2), 200 201. – Queensborough Community College of Omura, Y. (2004). 50 years of sunspot observation [in Japanese]. National Geographic, 10(7), 70 71. – New York. We thank the National Renshaw, S., & Ihara, S. (1997). Amateur astronomy in Japan, edited by Edwin L. Aguirre. Sky and Telescope, 93(3), 104 108. Museum of Nature and Science for Sato, T. (1972). Second conference of Japanese Jupiter observers. The Journal of the Association of Lunar and Planetary Observers, The Strolling – maintaining the database of Astronomer, 24,1 2. – “Observations of sunspots 1947-1996, Sato, A. (1997). Reminiscence of Mademoiselle Koyama [in Japanese]. The Heavens, 867, 221 222. Hisako Koyama,” and for providing Schmadel, L. D. (2012). Dictionary of Minor Planet Names (Sixth ed.) (265 pp.). Springer. https://doi.org/10.1007/978-3-642-29718-2 – reproductions of Ms. Koyama’s sunspot Shigehisa, O. (1995). Amateur astronomy club. In S. Morikubo, et al. (Eds.), History of Japanese amateur astronomy [in Japanese] (pp. 326 331). drawings, with all rights reserved. NCAR Tokyo: Nihon Kousei Sha. – is sponsored by the National Science Svalgaard, L., & Schatten, K. H. (2016). Reconstruction of the sunspot group number: The backbone method. Solar Physics, 291, 2653 2684. Foundation. Data related to this manu- https://doi.org/10.1007/s11207-015-0815 script can be found in the references Swinson, D. B., Humble, J. E., Shea, M. A., & Smart, D. F. (1991). Latitudinal cosmic ray gradients: Their relation to solar activity asymmetry. – provided and at http://www.kahaku.go. Journal of Geophysical Research, 96(A2), 1757 1765. https://doi.org/10.1029/90JA02502 – jp/research/db/science_engineering/ Swinson, D. B., Ko Koya Ma, H., & Saito, T. (1986). Long-term variations in north-south asymmetry of solar activity. Solar Physics, 106,35 42. sunspot/. https://doi.org/10.1007/BF00161351 Temmer, M., Rybák, J., Bendík, P., Veronig, A., Vogler, F., Otruba, W., … Hanslmeier, A. (2006). Hemispheric sunspot numbers {Rn} and {Rs} from 1945–2004: Catalogue and N-S asymmetry analysis for solar cycles 18–23. Astronomy & , 447, 735–743. https://doi.org/ 10.1051/0004-6361:20054060

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Temmer, M., Veronig, A., & Hanslmeier, A. (2002). Hemispheric sunspot numbers Rn and Rs: Catalogue and N-S asymmetry analysis. Astronomy and Astrophysics, 390(2), 707–715. https://doi.org/10.1051/0004-6361:20020758 Vaquero, J. M., Svalgaard, L., Carrasco, V. M. S., Clette, F., Lefèvre, L., Gallego, M. C., … Howe, R. (2016). A revised collection of sunspot group numbers. Solar Physics, 291(1–2), 3061–3074. https://doi.org/10.1007/s11207-016-0982-2 Wang, Y.-M. (2014). Solar cycle variation of the Sun’s low-order magnetic multipoles: Heliospheric consequences. Space Science Reviews, 186, 387–407. https://doi.org/10.1007/s11214-014-0051-9 Wang, Y.-M., & Robbrecht, E. (2011). Asymmetric sunspot activity and the southward displacement of the heliospheric current sheet. The Astrophysical Journal, 736, 136–147. https://doi.org/10.1088/0004-637X/736/2/136 Yallop, B. D. (1985). Book reviews, “Observations of sunspots 1947–1984, by Hisako Koyama”. The Observatory, 105, 241–242.

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