AURORA CATALOGUE 1 Dunstanburgh Castle, Northumberland, silhouetted by an auroral display on 16 February 2015. Downloaded from https://academic.oup.com/astrogeo/article/56/4/4.25/210105 by guest on 23 September 2021 An arch in the UK Mike Lockwood and Luke found 3090 newspaper reports of auroral Britain, the transition to the Gregorian cal- sightings, the most useful being regular endar was made on 25 March 1752 and so a Barnard report on a new monthly meteorological reports. The years correction of 11 days is needed for reports catalogue of auroral observations after 1923 have yet to be analysed, but are between 1700 and 1752, many of which made in the British Isles and Ireland. well reported in observatory yearbooks. were published in Philosophical Transactions. The yield from newspapers compares However, for other reports the correction with 5278 reports from the scientific lit- has already been made; care must be taken rches, streamers, polar lights, merry erature and 2034 from amateur observers. not to apply it twice. dancers… just a few of many names However, the largest contribution comes After removal of duplicates the dataset Aused to describe the aurora borealis from observatory yearbooks and reports, contains 17 761 independent reports from (figure 1) in historical documents in the which yielded 9239. Parish and county known locations between 1705 and 1950 UK. We have compiled a new catalogue archives have proved difficult to exploit (our on 7640 auroral nights (an average of 2.33 of 20 591 independent reports of auroral survey contains just 26 such per auroral night). For 1951 to sightings from the British Isles and Ireland reports); these are not widely “The dataset contains 1975 we do not, at the time of for 1700–1975 using observatory yearbooks, available in electronic form. 17 761 reports from writing, have the coordinates the diaries of amateur observers, news- We have added these to 2958 known locations from of individual sightings but paper reports and the scientific literature. reports of sightings from the 1705 to 1950” we do have summaries of the Our aim is to provide an independent data British Isles listed in previous totals as a function of latitude; series that can aid understanding of long- international surveys, in particular those by adding these allows us to identify 10 390 term solar variability, alongside cosmo- Fritz (1873, 1881) and Lovering (1868). auroral nights between 1705 and 1975. genic isotope data and historic records of This total of 20 591 reports contains dupli- geomagnetic activity and sunspots. cates of the same observation and so we Geomagnetic latitudes The most time-consuming part of this have stored details, wherever possible, such A feature of the British Isles is that they task has been sorting the newspaper as the observer’s name, the source and the cover a wide range of geomagnetic latitudes reports: a search of the British Newspaper location, to help identify these. The location – about 9° in all. The secular change in the Archive (compiled in partnership with the of a reported sighting tends to be general- geomagnetic field makes this spread of lati- British Library) for the term aurora borealis ized as it is copied from one catalogue to tudes a major advantage. To find the geo- revealed 13 673 articles. We have had to another. For example, many early sightings magnetic latitude of each location at a given sift out those relating to: racehorses and come from King’s Lynn (by Martin Folkes date we here use a spline of the Interna- ships of the same name; travelogues about and William Rastrick) but this is some- tional Geomagnetic Reference Field (IGRF) the polar regions; articles about scientific times generalized to “Norfolk” or even to and the gufm1 geomagnetic field models theories; articles and letters proposing false “England”: hence, one sighting can lead to (Jackson et al. 2000), with some smoothing associations with the weather; descriptions three or more, apparently different reports. to remove small discontinuities between of light shows, paintings and works of lit- Also, place names change: King’s Lynn the two at 1900. These models are used to erature; and advertisements for fireworks. has been referred to as Lynn, Lun, Lenn, compute the field inclination, i, which is We here define a “sighting” as a night on Lenne Regis, Lynn Regis, Len Episcopi and converted into a “dip” geomagnetic lati- which aurora was observed before dawn; Bishop’s Lynn. Metadata is also particularly tude, L, using the formula tan (L) = tan (i)/2. observations after midnight but before valuable in identifying observations that Values of L were evaluated at grid points dawn are given the date of the start of the have been duplicated because of the confu- with spacing 1° in latitude and 2° in lon- night before midnight. We have, so far, sion between Julian and Gregorian dates. In gitude and 2-dimensional interpolation A&G • August 2015 • Vol. 56 • www.astrongeo.com 4.25 AURORA CATALOGUE was used to derive L for the coordinates 68 of each observation. The left-hand panel of figure 2 showsL as a function of date 66 for various sites important in the history of auroral observations in the British Isles. 64 ) The right-hand panel shows the distri- o ( 62 bution in magnetic latitudes of auroral Λ observations from known sites (computed 60 in the same way) in seven catalogues from the northern hemisphere from 1650 to 1950. 58 The catalogues used are by Fritz (1873, 1881) Haroldswick and Lovering (1868) (both global), Silver- 56 Aberdeen man (New England), Silverman (all USA; see Silverman 1992), Rubenson (1879, 1882; 54 Edinburgh Sweden), Nevanlinna (1995; Finland) and Kendal 52 Downloaded from https://academic.oup.com/astrogeo/article/56/4/4.25/210105 by guest on 23 September 2021 the new catalogue described here (British geomagnetic dip latitude, Kings Lynn Isles and Ireland). The distribution shows a 50 marked peak at L between 57° and 63° (the London two dashed lines in the left-hand panel). 48 Plymouth The decay at L < 57° with decreasing L is probably accurate because throughout the 46 1650 1700 1750 1800 1850 1900 1950 2000 0 5 10 period there were many available observ- year N(Λ)dΛ/1000 ers at these latitudes. However, the decay at higher L may be influenced by a decrease 2 (Left): The geomagnetic dip latitude L of various sites in the British Isles as a function of date. in the available observers with increasing (Right): The distribution of auroral sightings with L (from well-specified locations taken from a basket of L. We here refer to the band of peak occur- seven catalogues from various longitudes in the northern hemisphere and including the new catalogue rence at 57° ≤ L ≤ 63° as the “auroral oval”. presented here): the number of sightings during 1650–1950 at magnetic latitudes between L and The large changes in L with time for a L + dL, N(L)dL, is shown as a function of L for dL = 1°. All magnetic latitudes are computed in the same given site are caused by the secular changes way from a spline of the IGRF and gufm1 models. in the geomagnetic field associated with the motions of the magnetic pole. The red observing locations moved poleward Scotland included: Rev. A C Henderson, line shows L for Haroldswick, on the Island to Edinburgh, Aberdeen and eventu- who made observations from Whalsay of Unst in Shetland, which was poleward of ally the Orkney, Hebrides and Shetland in Shetland, then from Buckie and Forfar, the auroral oval at the start of the interval islands. Given that these areas are sparsely between 1912 and 1918; and Rev. W M but has been within it since 1796. Aberdeen populated, one might have expected the Dunbar of Applegarth Manse, Dumfries was also poleward of the oval initially, but rate of auroral recordings to fall. That they (observations 1838–1848). But clergymen “moved” to lower L such that it was within did not has much to do with an engineer looking to the heavens (in more than one it for 1783–1853. Edinburgh was initially called Robert Stevenson and his three sons sense) was far from a new phenomenon; close to the poleward edge of the oval but David, Alan and Thomas who designed there are many prior examples from further moved equatorward of it in 1841. Ken- and built 55 lighthouses around Scotland south including: nonconformist preacher dal, King’s Lynn, London and Plymouth between 1811 and 1886. Lighthouse keepers William Rastrick (King’s Lynn, 1722–1726); were all within the oval at the start of the regularly reported aurorae until operations and Rev. William Derham (Upminster, interval, but moved equatorward of it (leav- became mechanised in the second half of Redbridge and Windsor, 1707–1728). ing the oval in 1824, 1796, 1788 and 1789, the 20th century. Between 1920 and 1950, There were also a great many secular respectively). As sites moved equatorward there were 813 auroral observations from amateurs such as physician Thomas of the oval in the geomagnetic reference lighthouses constructed by the Stevensons Hughes from Stroud, Gloucestershire, frame, the occurrence frequency of auroral and 1229 from all Scottish lighthouses. who recorded aurorae and meteorologi- sightings there fell. At the end of the Maun- cal information in his diaries from 1771 to der minimum (1715), centres of population Amateurs and gentlemen scientists 1813 (Harrison 2005). Those with inherited such as London, Plymouth and King’s Lynn Amateur observers also made vital con- wealth were able to devote themselves were ideally placed to observe aurorae. tributions. Anthony Johnson reported 300 to science.