Sporadic aurorae observed in East Asia

Abstract

Abstract. All the accessible auroral observations recorded in Chinese and Japanese histories during the interval AD 1840-1911 are investigated in detail. Most of these auroral records have never been translated into a Western language before. The East Asian auroral reports provide information on the date and approximate location of each auroral observation, together with limited scientific information on the characteristics of the auroral luminosity such as colour, duration, extent, position in the sky and approximate time of occurrence. The full translations of the original Chinese and Japanese auroral records are presented in an appendix, which contains bibliographic details of the various historical sources. (There are no known reliable Korean observations during this interval.) A second appendix discusses a few implausible "auroral" records, which have been rejected. The salient scientific properties of all exactly dated and reliable East Asian auroral observations in the interval AD 1840-1911 are summarised succinctly. By comparing the relevant scientific information on exactly dated auroral observations with the lists of great geomagnetic storms compiled by the Royal Greenwich Observatory, and also the tabulated values of the Ak (Helsinki) and aa (Greenwich and Melbourne) magnetic indices, it is found that 5 of the great geomagnetic storms (aa>150 or Ak>50) during either the second half of the nineteenth century or the first decade of the twentieth century are clearly identified by extensive auroral displays observed in China or Japan. Indeed, two of these great storms produced auroral displays observed in both countries on the same night. Conversely, at least 29 (69%) of the 42 Chinese and Japanese auroral observations occurred at times of weak-to-moderate geomagnetic activity (aa or Ak≤50). It is shown that these latter auroral displays are very similar to the more numerous (about 50) examples of sporadic aurorae observed in the United States during the interval AD 1880-1940. The loCorrespondence to: D. M. Willis (d.m.willis@rl.ac.uk) calised nature and spatial structure of some sporadic aurorae observed in East Asia is indicated by the use of descriptive terms such as "lightning", "rainbow", "streak" and "grid".

Sporadic aurora from Spain

“…Nevertheless, low-latitude aurorae have been observed also during periods of weak-tomoderate geomagnetic activity, and this phenomenon has been described and catalogued for the North America (Silverman, 2003) and East Asia (Willis et al, 2007) regions. Silverman (2003) showed and analyzed US auroral data from 1880 to 1940 to demonstrate the reality of an auroral phenomenon with two important characteristics: (a) it occurred under conditions of quiet or moderate magnetic activity and (b) it occurred at low-latitudes where auroras normally do not occur except during great magnetic storms.…”

“…It should be stressed that, up to now there has been no identification of sporadic auroral events over Europe. In fact, the aggregated number of similar lowlatitude auroras that have occurred under weak-to-moderate magnetic activity is fairly small (Abbe, 1895;Botley, 1963;Silverman, 2003;Willis et al, 2007).…”

“…69%) occurred at times of weak-to-moderate geomagnetic activity (aa or Ak index ≤ 50). Willis et al (2007) have suggested the possible connection of sporadic aurorae with solar activity but further reCopy right c The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB.…”

“…Silverman (2003) used the term "Sporadic aurora" previously adopted in the literature dedicated to this rare type of aurora (Abbe, 1895;Botley, 1963). According to Willis et al (2007) the word "sporadic aurorae" may be used to describe localised auroral displays that occur at low geomagnetic latitudes (approximately, −45…”

“…Far eastern Asian countries have kept good records of low latitude auroras observed in the last millennium, namely over Japan (Nakazawa et al, 2004), Korea (Zhang, 1985) and China (Yau et al, 1995). Recently, Willis et al (2007) have compiled 42 Chinese and Japanese auroral observations from 1840 to 1911. They have demonstrated that at least 29 out of the 42 Chinese and Japanese auroral observations (i.e.…”