I am a research geophysicist in the Geomagnetism Program of the U.S. Geological Survey (USGS). My work, often accomplished in collaboration with colleagues, is focused on: 1. Using geomagnetic monitoring data and magnetotelluric survey data to evaluate geoelectric hazards of concern to the electric-power grid industry. 2. Statistical analysis of the rare occurrences of intense magnetic storms. 3. Analysis of historical records of past magnetic storms and their impacts.
The March 1940 superstorm
Love et al. (2023) reports on the great magnetic storm of 24 March 1940 and its impacts. The storm was caused by pair of concentrated, and possibly interacting, bursts of solar wind. Geomagnetic field variation during the storm induced high-amplitude geoelectric fields in the solid Earth’s conducting interior. These geoelectric fields drove uncontrolled currents in grounded long-wire communication- and electricity-power-transmission systems in the United States and Canada, causing significant operational interference in those systems. This interference was primarily experienced in the upper Midwest and the eastern United States, and many incidents of interference were reported in the popular press. Voltages monitored on several lines were greater than studies estimate would have occurred during the great storm of March 1989. In terms of its impact on communication and power systems, the March 1940 magnetic storm was one of the most significant ever experienced by the United States. Modern communication systems are less dependent on long electrically conducting transmission lines. On the other hand, modern electric-power-transmission systems are more dependent on such lines, and they, thus, might experience interference with the future occurrence of a storm like that of March 1940.
Love, J. J., Rigler, E. J., Hartinger, M. D., Lucas, G. M., Kelbert, A. & Bedrosian, P. A., 2023. The March 1940 superstorm: Geoelectromagnetic hazards and impacts on American communication and power systems, Space Weather, 21(6), e2022SW003379. doi:10.1029/2022SW003379. [Link] [Spaceweather.com]
Mapping the March 1989 magnetic superstorm
Love et al. (2022) reports on an analysis of the March 1989 magnetic superstorm. Electric fields induced in the Earth during magnetic storms can drive uncontrolled currents in electric-power systems, interfering with their operation. Geomagnetically induced currents during the magnetic storm of March 1989 caused a blackout in Quebec, and, in the Mid-Atlantic and Northeast United States, they caused operational interference for electric-power companies and damaged a high-voltage transformer. In support of projects for estimating geoelectric hazards and improving power-system resilience, maps are made of March 1989 magnetic-storm geoelectric hazards and corresponding impacts on United States power systems. Results are based on modeling geomagnetic monitoring data, geoelectromagnetic survey data, and published reports of power-system interference. During the storm, electric-power system interference was concentrated where the lithosphere is relatively electrically resistive, and when and where the geoelectric field was of high amplitude. This was particularly true in the Mid-Atlantic and Northeast, near many of America’s largest cities, and in the upper Midwest. Retrospective analyses, such as this one for the March 1989 storm, show where utility companies might concentrate their efforts to mitigate the impacts of future magnetic superstorms.
Love, J. J., Lucas, G. M., Rigler, E. J., Murphy, B. S., Kelbert, A. & Bedrosian, P. A., 2022. Mapping a magnetic superstorm: March 1989 geoelectric hazards and impacts on United States power systems. Space Weather, 20, e2021SW003030, doi:10.1029/2021SW003030. [Link] [EarthSky] [Spaceweather.com]
Down to Earth with nuclear electromagnetic pulse (EMP)
Love et al. (2021) reports on the effects that realistic Earth-surface impedance can have on EMP-induced geoelectric fields. A nuclear explosion in the near-Earth space environment can produce an electromagnetic pulse (EMP) at the Earth’s surface. A low-frequency part of the EMP signal, known as E3 and covering periods from about a tenth of a second to a few hundred seconds, can induce geoelectric fields in the conducting solid Earth, interfering with the operation of electricity power grids. To investigate this, accurate estimates are required of the Earth’s surface impedance – that is, the relationship between geomagnetic and geoelectric field variation. Surface impedance is a function of the electrical conductivity of subsurface rock structures. Using impedance tensors obtained from survey measurements, time-dependent scenario maps are constructed of the E3 geoelectric fields and power-grid geovoltages that would be generated by a hypothetical nuclear explosion above the United States. Over the course of the scenario, geoelectric amplitude, polarization, and variational phase are shown to differ significantly from one location to another, mostly as the result of geographic granularity in impedance. It is concluded that extremely simple impedance models, such as those widely used in government and industry reports concerned with power-grid vulnerability assessment, do not provide accurate estimates of the E3 geoelectric hazard in complex geological settings. This research, reported in the popular press, informs utility company projects for assessing grid vulnerability and improving grid resilience to nuclear electromagnetic pulse.
Love, J. J., Lucas, G. M., Murphy, B. S., Bedrosian, P. A., Rigler, E. J. & Kelbert, A., 2021. Down to Earth with nuclear electromagnetic pulse: Realistic surface impedance affects mapping of the E3 geoelectric hazard. Earth and Space Science, 8(8), e2021EA001792, doi:10.1029/2021EA001792. [Link] [Futura Sciences] [IEEE Spectrum] [Spaceweather.com] [Tendencias] [USGS Technical Announcement]
Geoelectric Hazard Maps
Love et al. (2019) and Lucas et al. (2020) are research reports on analyses of geoelectric hazards for the contiguous United States. Lucas et al., in particular, gives a hazard map showing maximum 1-minute duration, quasi-DC voltages that would be induced on the national electric power grid by a rare (100-year) geomagnetic superstorm. These extreme-value voltages are a function of geomagnetic disturbance, Earth-surface impedance (which is, itself, a function of geological structure), and grid topology. Across the northern Midwest and across the Piedmont formation, east of the Appalachian Mountains, these 100-year voltages are potentially high enough to disrupt grid operations and damage high-voltage transformers. Notably, the high hazards in the East are adjacent to many of the nation’s largest cities. This research, reported in the popular press, informs utility company projects for assessing grid vulnerability and improving grid resilience to magnetic storm hazards.
Love, J. J., Lucas, G., Bedrosian, P. A. & Kelbert, A., 2019. Extreme‐value geoelectric amplitude and polarization across the Northeast United States, Space Weather, 17(3), 379-395, doi:10.1029/2018SW002068. [Link] [National Geographic] [Science Alert] [Scientific American] [USGS]
Lucas, G. M., Love, J. J., Kelbert, A., Bedrosian, P. A. & Rigler, E. J., 2020. A 100-year geoelectric hazard analysis for the U.S. high-voltage power grid, Space Weather, 18(2), e2019SW002329, doi:10.1029/2019SW002329. [Link] [EnergyWire] [Gizmodo] [IEEE Spectrum] [Physics World] [Spaceweather.com]
The May 1921 Magnetic Superstorm
Love et al. (2019) reports on an analysis of historical magnetograms recording the magnetic superstorm of May 1921. For the first time, a reliable estimate is obtained of the Dst ring-current index time series for this notable storm. The storm was apparently driven by a series of interplanetary coronal mass ejections. Over its course, the storm exhibited substantial local-time (longitude) asymmetry in low‐latitude geomagnetic disturbance, something that can be attributed to substorm disturbance. The storm attained an estimated maximum -Dst intensity of 907 nT — a value comparable to the Carrington event of 1859. The 1921 storm brought spectacular aurorae to the nighttime sky. It also interfered with and damaged telephone and telegraph systems associated with railroads in New York City and State. These latter effects were due to a combination of three factors: the localized details of geomagnetic vector disturbance, the geographic expression of the Earth’s surface impedance, and the configurations and physical parameters of the electrical networks of the day. This research, reported in the popular press, informs modern projects for assessing and mitigating the effects of magnetic storms that might occur in the future.
Love, J. J., Hayakawa, H. & Cliver, E. W., 2019. Intensity and impact of the New York Railroad Superstorm of May 1921, Space Weather, 17(8), 1281-1292, doi:10.1029/2019SW002250. [Link] [Astronomy Magazine] [Knowable Magazine] [Scientific American] [Spaceweather.com] [Stuff (New Zealand)] [The Independent]
Magnetic superstorms like March 1989 more frequent than previously thought
Past and possible future magnetic storm intensities are investigated in a new report by Love (2021). As part of this work, a dataset is developed of the most intense and second most intense storms for each of the past eleven solar cycles (1902-2016) — augmenting a traditional dataset that only covers the past six solar cycles (1957-2016) with recently published intensities for several magnetic superstorms and with new storm intensity estimates. These data are analyzed using statistical methods that provide estimates of the probability of future magnetic superstorms. A storm as intense as that of March 1989, which caused widespread disruption of technological systems and an electricity blackout in Québec, Canada, is predicted to occur, on average, about every four solar cycles. This is twice as often as estimated using only the traditional shorter dataset.
Love, J. J., 2021. Extreme‐event magnetic storm probabilities derived from rank statistics of historical Dst intensities for solar cycles 14‐24. Space Weather, 19(4), e2020SW002579, doi:10.1029/2020SW002579. [Link] [Spaceweather.com]
Love, J. J., 2020. Some experiments in extreme-value statistical modeling of magnetic superstorm intensities, Space Weather, 18(1), e2019SW002255, doi:10.1029/2019SW002255. [Link]
Geomagnetic detection of heliomagnetic structure
Love et al. (2012) reports on an analysis of the geomagnetic‐activity aa-index covering solar cycle 11 to the beginning of 24, 1868–2011. Autocorrelation plots show 27.0‐d recurrent geomagnetic activity that is well-known to be driven by high-speed streams of solar wind emitted from semi-persistent coronal holes — 27.0 d is the solar rotation period, and with each rotation, the Sun which brings the stream around to the Earth with the same period. This periodicity in geomagnetic disturbance is most prominently seen during solar‐cycle minima. Some minima also exhibit a 13.5‐d recurrence geomagnetic disturbance, which can be attributed to a tilted poloidal dipole ingredient in the solar magnetic field — streams of plasma flowing from each pole. Previous work has shown that the solar-cycle minimum 23–24 exhibited 9.0 and 6.7‐d recurrence in geomagnetic and heliospheric data, but those recurrence intervals were not prominently present during the preceding minima of 21–22 and 22–23. Using annual‐averages and solar‐cycle averages of autocorrelations of the historical aa data, we put these observations into a long‐term perspective: none of the 12 minima preceding 23–24 exhibited prominent 9.0 and 6.7‐d geomagnetic activity recurrence. We show that the detection of these recurrence intervals can be traced to an unusual combination of sectorial spherical‐harmonic structure in the solar magnetic field and anomalously low sunspot number. We speculate that 9.0 and 6.7‐d recurrence is related to
Love, J. J., Rigler, E. J. & Gibson, S. E., 2012. Geomagnetic detection of the sectorial solar magnetic field and the historical peculiarity of minimum 23-24, Geophys. Res. Lett., 39(4), L04102, doi:10.1029/2012GL050702. [Link][GRL]
On the insignificance of Herschel’s sunspot correlation
Love (2013) examines William Herschel’s hypothesis that solar-cycle variation of Sun’s irradiance has a modulating effect on the Earth’s climate and that this is, specifically, manifested as an anticorrelation between sunspot number and the market price of wheat. Since Herschel first proposed his hypothesis in 1801, it has been regarded with both interest and skepticism. Recently, reports have been published that appear to either support Herschel’s hypothesis or rely on its validity. Using statistical methods, Love shows that correlations between sunspot number and wheat yield and wheat price would be very likely realizations of random data; these correlations are “insignificant.” Therefore, Herschel’s hypothesis must be regarded with skepticism.
Love, J. J., 2013. On the insignificance of Herschel’s sunspot correlation, Geophys. Res. Lett., 40(16), 4171-4176, doi:10.1002/grl.50846. [Link] [AGU] [RealClimate]
The Magnetic Superstorm of September 1909
Love et al. (2019) examines historical records of solar observations and ground-level geomagnetic disturbance for the magnetic superstorm of 25 September 1909. This storm was initiated by the arrival, at Earth, of a shock wave in the solar wind that can be linked to the ejection of plasma from a sunspot active region. The 1909 storm was one of the most intense of the twentieth century. It exhibited violent levels of geomagnetic disturbance (with a minimum Dst value of −595 nT), caused widespread interference to telegraph systems, and brought spectacular aurorae to the nighttime sky. Results reported inform projects focused on understanding and mitigating the deleterious effects of extreme space-weather events to technological systems of importance to modern society.
Love, J. J., Hayakawa, H. & Cliver, E. W., 2019. On the intensity of the magnetic superstorm of September 1909, Space Weather, 17(1), 37-45, doi:10.1029/2018SW002079. [Link]