Results of Russian geomagnetic observatories in the 19th century: magnetic activity, 1841–1862

Abstract

Abstract. Hourly (spot readings) magnetic data (H-and Dcomponents) were digitized from Russian yearbook tables for the years 1850-1862 from four observatories. The pdf pictures for digitization were taken by a normal digital camera. The database obtained consists of about 900 000 single data points. The time series of hourly magnetic values reveal slow secular variations (declination only) as well as transient and regular geomagnetic variations of external origin. The quality and homogeneity of the data is satisfactory. Daily Ak-indices were calculated using the index algorithm that has been earlier applied to 19th century data from Helsinki (Finland) as well as modern magnetic observatory recordings. The activity index series derived from the Russian data is consistent with earlier activity index series for 1850-1862. The digitized index data series derived in this study was extended back to 1841 by including magnetic C9 activity index data available from a Russian observatory (St. Petersburg). Magnetic data rescued here is well suitable for various reconstructions for studies of the long-term variation of the space weather in the 19th century.

Russian geomagnetic recordings in 1850–1862 compared to modern observations

“…Around the mid of 1800s, seven Russian observatories were in operation in the northern hemisphere (Nevanlinna & Häkkinen 2010). We use four of them in this study covering the years 1850-1862 (Fig.…”

“…However, we considered the time series as a whole without separating it into two parts. Concerning the original time stamping, in the Russian yearbooks the time in hourly observations was given in the Göttingen time until 1856 (1857 in St. Petersburg) and later in local solar time (Nevanlinna & Häkkinen 2010). Göttingen time leads by 0.66 h the present day Universal Time (UT).…”

“…However, compared to Nevanlinna & Häkkinen (2010), we performed a slightly more accurate conversion of the original recordings to get the transverse magnetic north (H) and east (E) components of the horizontal field vector (H). For the east component, Nevanlinna & Häkkinen (2010) applied the approximation…”

“…5) supports this, and also shows that the instruments at STP obviously produced reliable data. Since the equipment was identical at all Russian observatories, we can consider the data quality as good (Nevanlinna & Häkkinen 2010). For TAR and DOU, we constructed time series of 1-h spot readings in 2002-2012 in the same way as for NUR.…”

Magnetic Observatory Data and Metadata: Types and Availability

“…Various attempts have been made at this, including the scanning techniques of Optical Character Recognition (OCR). The unreliability of this procedure, especially for HMV tables (generally due to the high variability of different typefaces and hand-written entries in the tables), caused these efforts to be directed more toward manual entry and checking (see for example, Nagarajan, 2008;Fouassier and Chulliat, 2009;Nevanlinna and Häkkinen, 2010). While the reliability of this manual procedure is very good, it is also labour intensive and can therefore be expensive.…”