Annual number of solar radio bursts from 1996 to 2010 at eight different frequencies that exceed 1000 solar flare units (SFU). Bursts with fluxes exceeding this value are generally called “great bursts.” The reasons from the large number of bursts at lower frequencies are not yet fully understood. Credit: Giersch et al, 2017, Figure 5
Source: Space Weather

Noting the threats from large radio bursts to Global Navigation Satellite System (GNSS) receivers and other radio technology systems, Giersch et al. [2017] have undertaken a comprehensive survey of the solar radio data archives of NOAA’s National Centers for Environmental Information. The burst archives, which are used by most researchers in analyzing and producing statistics on solar radio burst phenomena, were created from records submitted by the United States Air Force Radio Solar Telescope Network (RSTN). RSTN operates at eight frequencies between 245 MHz and 15400 MHz at four sites globally.

The authors find that the burst records indicate under-reporting from some stations. Despite these shortcomings, this paper reveals that different solar cycles may show statistically different distributions in burst activity and that it is a mistake to assume that the Sun shows similar radio burst behavior in different sunspot cycles. The authors computed burst rates for different frequencies by computing power law probability distributions of the burst peak fluxes. They estimate that approximately two bursts per decade could exceed 105 solar flux units, a value commonly used as a threshold for potential compromise of the GNSS network. They also note that large solar radio bursts are not confined to the period around sunspot maximum, and prediction of such events that utilize historical data will invariably be an underestimate due to archive data deficiencies.

This article is relevant to space weather benchmarks under consideration by the US Space Weather Operations, Research and Mitigation (SWORM) Subcommittee of the National Science and Technology Council.

Citation: Giersch, O. D., Kennewell, J., & Lynch, M. (2017). Solar radio burst statistics and implications for space weather effects. Space Weather, 15.

—Delores J. Knipp, Editor-in-Chief, Space Weather

Text © 2017. The authors. CC BY-NC-ND 3.0
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