the gross domestic product alone put total economic costs in the $3 billion to $6 billion range,6 which is comparable to the damage caused by a major natural disaster such as Hurricane Hugo. The Northeast, in fact, was found to be particularly vulnerable to GICs. Protections can be installed, but it is impossible to completely protect an extensive power grid from GIC effects. However, evasive measures (such as rerouting the distribution) can be taken if there is sufficient warning and the power industry is prepared to respond.7


The United States, together with its European and Japanese partners, has succeeded in placing instrumentation in space and on the ground that is capable of tracing the course of a solar event from the Sun to its effects on the geospace environment and beyond. These space-and ground-based facilities include key elements outlined in Table 1, Table 2, and Table 3.

Instruments on UARS are continuing a two-decade time-series of space-based measurements of the solar constant.8 However, neither the UARS measurements nor those currently being considered as part of the EOS or National Polar-orbiting Environmental Satellite System (NPOESS) programs can elucidate the souce(s) of solar irradiance variability. Images in various spectral lines and bands obtained on SOHO have already revealed the wealth of different features on the Sun and hint at their control by solar magnetism. Assuming the continued operation of UARS and its solar irradiance monitor, we will have the opportunity to observe simultaneously how different solar features evolve with the changes in the solar magnetic field and affect the total irradiance. These observations will finally allow us to identify the sources of solar irradiance variations across a large part of the solar spectrum.

With SOHO, Yohkoh, Winf, IMP-8, and ACE, researchers can begin to distinguish among the varying causes and effects of flares and CMEs as the frequencies of both increase with increasing sunspot number. Using helioseismology techniques on SOHO and from complementary ground-based observatories such as the Global Oscillations Network Group (GONG), we can also begin to understand how the solar dynamo produces the diversity of solar features that affect life on Earth: sunspots, faculae and the active network that make the solar constant a variable; flares with their complex sunspot region connection and their many energetic


Hurricane Hugo struck the Carolinas in 1989, causing an estimated $5 billion in property damage, according to the Federal Emergency Management Agency (FEMA). See “FEMA/City to Fund Charleston Storm System Upgrade,” News: FEMA News Room, Aug. 6, 1996. The damage estimates for a magnetic storm are taken from P.R. Barnes and J.W. Van Dyke, “Potential Economic Costs from Geomagnetic Storms,” Geomagnetic Storm Cycle 22: Power System Problems on the Horizon: Special Panel Session Report, Institute of Electrical and Electronic Engineers Power Engineering Society (IEEE PES) Summer Meeting, Transmission and Distribution Committee of the IEEE PES, June 17, 1990, Minneapolis, Minnesota.


John G. Kappenman, Lawrence J. Zanetti, and William A. Radasky, “Geomagnetic Storm Forecasts and the Power Industry,” Eos, Trans. Am. Geophys. Union, January 28, 1997.


As this report was being completed, NASA announced the opportunity to conduct a Total Solar Irradiance Mission (TSIM) as part of the Earth Observing System program. TSIM is planned to continue the precise total solar irradiance data record measured by NASA-funded spaceborne instruments since 1979. A December 2001 launch is planned.

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