Value of Historical Space Weather Events

Abstract

The recent publication in this journal of a research paper on the 1859 solar storm (S. F. Odenwald and J. L. Green, Space Weather, 5, S06002, doi:10.1029/2006SW000262, 2007) demonstrates that revisiting historical events can be a useful way in which to gain an understanding of contemporary issues in space weather. The intense geomagnetic disturbances following the solar activity in late August–early September 1859, including the first observation of a white light flare by Richard Carrington, have long been recognized to be among the largest recorded in the past century and a half. Although the effect of auroras on electrical telegraph systems had first been noticed as early as 1847, it was the widespread disturbances in Europe and the eastern United States from the 1859 events that provided the impetus for engineers to work on mitigation strategies. The 1859 events also demonstrated the need for more fundamental understanding of the causes that could produce the “anomalous” currents on the telegraph systems. While reviewing Odenwald and Green's manuscript submission, I was prompted to take down my copy of George Prescott's History, Theory, and Practice of the Electrical Telegraph, published by Ticknor and Fields in 1860, the year following Carrington's flare event. The telegraph is a once-modern technology that is now quite obsolete. At the time, it was a communication marvel, and Prescott was moved not only to write about the technical details of building telegraph systems (wires and batteries and keys and receivers), but also to explain to the public the phenomena of electricity and magnetism. This included the recently discovered effect of induced currents by Faraday in 1832. One chapter of Prescott describes “Working telegraph lines with auroral magnetism” (that is, the operation of a telegraph line under the influence of only auroral activity). This chapter is “space weather” in the era of the most modern (and only) electrical technology of the time. Prescott outlined then-current ideas of the cause or causes of the aurora followed by vivid contemporary descriptions of the effects from induced currents in the lines of various telegraph systems in the late 1840s through the 1850s. These disturbances originated from the same physical processes that today produce disturbances in power system grids, long communication cables, and pipelines. These natural processes are also analogs of the induced currents that were generated by the electromagnetic pulse following the United States's Starfish Prime high-altitude nuclear explosion of 1962. The sizes of the induced currents that might be measured in a long grounded conductor depend upon the magnitude and nature of the fluctuating ionosphere currents and the conductivity of the ground below. An unknown in planning a new long-conductor route is the extremes of the space-induced currents that might occur over the route. Historical information in the form of actual data records from a few large geomagnetic events in the twentieth century have previously been used for this purpose. It is likely that a clever analysis could be made of the telegraph routes of the disturbance effects from the mid nineteenth century, and especially from the 1859 period, in order to provide rough estimates of induced Earth currents resulting from these geomagnetic events. Such information would add to the presently limited set of historical extremes currently available and would be another contribution by the 1859 event to contemporary space weather. Louis J. Lanzerotti is editor of Space Weather, a distinguished research professor at the New Jersey Institute of Technology, and a consultant at Alcatel-Lucent Technologies’ Bell Laboratories.