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The Extreme Space Weather Event of 1872 February: Sunspots, Magnetic Disturbance, and Auroral Displays
Hisashi Hayakawa, Edward W. Cliver, Frédéric Clette +19
We review observations of solar activity, geomagnetic variation, and auroral visibility for the extreme geomagnetic storm on 1872 February 4. The extreme storm (referred to here as…
Re-calibration of the Sunspot Number: Status Report
F. Clette, L. Lefèvre, T. Chatzistergos +18
We report progress on the ongoing recalibration of the Wolf sunspot number (SN) and Group sunspot number (GN) following the release of version 2.0 of SN in 2015. This report consti…
Scale Transfer in 1849 : Heinrich Schwabe to Rudolf Wolf
Shreya Bhattacharya, Laure Lefevre, Hisashi Hayakawa +2
The focus of this study is to reveal the reason behind a scale problem detected around 1849 in the historical version of the International Sunspot Number Series, i.e. version 1 (Le…
A Review for Japanese auroral records on the three extreme space weather events around the International Geophysical Year (1957 -- 1958)
Hisashi Hayakawa, Yusuke Ebihara, Hidetoshi Hata
Solar Cycle 19 was probably the greatest solar cycle over the last four centuries and significantly disrupted the solar-terrestrial environments with a number of solar eruptions an…
Temporal Variations of the Three Geomagnetic Field Components at Colaba Observatory around the Carrington Storm in 1859
Hisashi Hayakawa, Heikki Nevanlinna, Séan P. Blake +3
The Carrington storm in 1859 September has been arguably identified as the greatest geomagnetic storm ever recorded. However, its exact magnitude and chronology remain controversia…
Stephan Prantner's Sunspot Observations during the Dalton Minimum
Hisashi Hayakawa, Shoma Uneme, Bruno P. Besser +2
In addition to regular Schwabe cycles (~ 11 years), solar activity also shows longer periods of enhanced or reduced activity. Of these, reconstructions of the Dalton Minimum provid…
Daniel Mögling's sunspot observations in 1626 - 1629: A manuscript reference for the solar activity before the Maunder Minimum
Hisashi Hayakawa, Tomoya Iju, Koji Murata +1
The sunspot groups have been observed since 1610 and their numbers have been used for evaluating the amplitude of solar activity. Daniel Mögling recorded his sunspot observations f…
The Dalton Minimum and John Dalton's Auroral Observations
Sam M. Silverman, Hisashi Hayakawa
In addition to the regular Schwabe cycles of approximately 11 y, "prolonged solar activity minima" have been identified through the direct observation of sunspots and aurorae, as w…
The intensity and evolution of the extreme storms in January 1938
Hisashi Hayakawa, Kentaro Hattori, Alexei A. Pevtsov +7
Major solar eruptions occasionally direct interplanetary coronal mass ejections (ICMEs) to Earth and cause significant geomagnetic storms and low-latitude aurorae. While single ext…
Reanalyses of the Sunspot Observations of Fogelius and Siverus: Two "Long-Term" Observers during the Maunder Minimum
Hisashi Hayakawa, Tomoya Iju, Shoma Uneme +3
The solar activity during the Maunder Minimum (MM; 1645 -- 1715) has been considered significantly different from the one captured in modern observations, in terms of sunspot group…
Candidate Auroral Observations during the Major Solar-Terrestrial Storm in May 1680: Implication for Space Weather Events during the Maunder Minimum
Hisashi Hayakawa, Kristian Schlegel, Bruno P. Besser +1
The Maunder Minimum (1645-1715) is currently considered the only grand minimum within telescopic sunspot observations since 1610. During this epoch, the Sun was extremely quiet and…
South American auroral reports during the Carrington storm
Hisashi Hayakawa, José R. Ribeiro, Yusuke Ebihara +2
The importance of the investigation of magnetic superstorms is not limited to academic interest, because these superstorms can cause catastrophic impact on the modern civilisation…
The Solar Corona during the Total Eclipse on 16 June 1806: Graphical Evidence of the Coronal Structure during the Dalton Minimum
Hisashi Hayakawa, Mathew J. Owens, Michael Lockwood +1
Visible coronal structure, in particular the spatial evolution of coronal streamers, provides indirect information about solar magnetic activity and the underlying solar dynamo. Th…
The Extreme Space Weather Event in 1903 October/November: An Outburst from the Quiet Sun
Hisashi Hayakawa, Paulo Ribeiro, José M. Vaquero +11
While the Sun is generally more eruptive during its maximum and declining phases, observational evidence shows certain cases of powerful solar eruptions during the quiet phase of t…
Thaddäus Derfflinger's sunspot observations during 1802-1824: A primary reference to understand the Dalton Minimum
Hisashi Hayakawa, Bruno P. Besser, Tomoya Iju +5
As we are heading towards the next solar cycle, presumably with a relatively small amplitude, it is of significant interest to reconstruct and describe the past grand minima on the…
Sunspot Observations by Hisako Koyama: 1945-1996
Hisashi Hayakawa, Frédéric Clette, Toshihiro Horaguchi +4
The sunspot record is the only observational tracer of solar activity that provides a fundamental, multi-century reference. Its homogeneity has been largely maintained with a succe…
The Earliest Candidates of Auroral Observations in Assyrian Astrological Reports: Insights on Solar Activity around 660 BCE
Hisashi Hayakawa, Yasuyuki Mitsuma, Yusuke Ebihara +1
Auroral records found in historical archives and cosmogenic isotopes found in natural archives have served as sound proxies of coronal mass ejections (CMEs) and solar energetic par…
Temporal and Spatial Evolutions of a Large Sunspot Group and Great Auroral Storms around the Carrington Event in 1859
Hisashi Hayakawa, Yusuke Ebihara, David M. Willis +10
The Carrington event is considered to be one of the most extreme space weather events in observational history within a series of magnetic storms caused by extreme interplanetary c…
A Transit of Venus Possibly Misinterpreted as an Unaided-Eye Sunspot Observation in China on 9 December 1874
Hisashi Hayakawa, Mitsuru Sôma, Kiyotaka Tanikawa +6
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 appearanc…
Occurrence of Great Magnetic Storms on 6-8 March 1582
Kentaro Hattori, Hisashi Hayakawa, Yusuke Ebihara
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 observ…
Intense geomagnetic storm during Maunder minimum possibly by a quiescent filament eruption
Hiroaki Isobe, Yusuke Ebihara, Akito D. Kawamura +2
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 m…
Revisiting Kunitomo's Sunspot Drawings during 1835-1836 in Japan
Masashi Fujiyama, Hisashi Hayakawa, Tomoya Iju +7
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 drawin…
Lifetimes and Emergence/Decay Rates of Star Spots on Solar-type Stars Estimated by Kepler Data in Comparison with Those of Sunspots
Kosuke Namekata, Hiroyuki Maehara, Yuta Notsu +7
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 Ke…
A Great Space Weather Event in February 1730
Hisashi Hayakawa, Yusuke Ebihara, José M. Vaquero +9
Aims. Historical records provide evidence of extreme magnetic storms with equatorward auroral extensions before the epoch of systematic magnetic observations. One significant magne…