In this study, we examine the relationships between the National Oceanic and Atmospheric Administration (NOAA) space weather scale frequencies and the maximum monthly sunspot number in each solar cycle: 1975 to 2020 for radio blackouts (R scales) and solar radiation storms (S scales), 1932 to 2020 for geomagnetic storms (G scales). Our main results are as follows. First, we find that NOAA space weather scale frequencies have strong solar cycle dependencies. Second, we propose new linear relationships between the frequency of certain scales (R1 to R4, and G1 to G4) and the maximum monthly sunspot number. T-test results show that R1 to R3 and G1 to G4 relationships are statistically meaningful, but marginal for R4. Third, our results significantly reduce the root-mean-square error (RMSE) between observed and suggested frequencies compared to the NOAA’s current frequencies. For example, in the case of solar cycle 24, our new prediction (74) for R3 scale is much more consistent with the observational frequency (74) than the NOAA prediction (175), and our prediction (85) for G3 scale is much closer to the observation (40) than the NOAA prediction (200). Our work may provide a useful guideline for advancing the space weather scales.

Introduction
Data
Method
    Correlation Analysis and Linear Regression
    T-Test
Result
Summary and Conclusion
Acknowledgments
References

• Daeil Kim(School of Space Research, Kyung Hee University, Yongin 17104, Republic of Korea)
• Yong-Jae Moon(School of Space Research, Kyung Hee University, Yongin 17104, Republic of Korea, Department of Astronomy and Space Science, Kyung Hee University, Yongin 17104, Republic of Korea) Corresponding author
• Jihyeon Son(Department of Astronomy and Space Science, Kyung Hee University, Yongin 17104, Republic of Korea)
• Hyun-Jin Jeong(School of Space Research, Kyung Hee University, Yongin 17104, Republic of Korea, Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium)