Variation of Geomagnetic Index Empirical Distribution and Burst Statistics Across Successive Solar Cycles

Bergin, Aisling; Chapman, Sandra C.; Moloney, Nicholas R.; Watkins, Nicholas W.

doi:10.1029/2021ja029986

Cited by 7 publications

(4 citation statements)

References 62 publications

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“…The NBL fit parameter does not track the variation in activity (smoothed SSN), of the last four solar cycles in the IMF at L1, in SME or SMR. The distribution of solar wind parameters do show solar cycle variation [Tindale & Chapman, 2016] and the top few percent of the data records of both AE and SMR also track the solar cycle [Bergin et al, 2022]. Auroral indices such as AE and SME sample the ground magnetic perturbations from high-latitude current systems, the largest of which are the auroral electrojets.…”

Section: Discussionmentioning

confidence: 98%

Newcomb-Benford Law characterization of solar wind magnetic field and geomagnetic indices

Benedito-Nunes

Gamper

Chapman

et al. 2023

Preprint

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The Newcomb-Benford Law (NBL) prescribes the probability distribution of the first digit of variables which explore a broad range under conditions including aggregation. Long-term space weather relevant observations and indices necessarily incorporate changes in the contributing number and types of observing instrumentation over time and we find that this can be detected solely by comparison with the NBL. It detects when upstream solar wind magnetic field OMNI HRO Interplanetary Magnetic Field incorporated new data from WIND and ACE after 1995. NBL comparison can detect underlying changes in geomagnetic indices AE (activity dependent background subtraction) and SME (different station types) that select individual stations showing the largest deflection, but not where station data are averaged, as in the SMR index. As composite indices becomes more widespread across the geosciences, the NBL may provide a generic data flag to indicate changes in the constituent raw data, calibration or sampling method.

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Section: Discussionmentioning

confidence: 98%

Newcomb-Benford Law characterization of solar wind magnetic field and geomagnetic indices

Benedito-Nunes

Gamper

Chapman

et al. 2023

Preprint

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“…Overall geomagnetic activity as seen in the aa index tracks the solar cycle variation in solar activity 12 , 13 , and overall levels of geomagnetic activity can be good solar cycle predictors 14 , 15 . The aa index is however highly discretized 16 , 17 ; high fidelity geomagnetic data, available over the last 4–5 cycles confirm that the high quantiles of geomagnetic activity track the variation in solar activity both within and between solar cycles 17 – 19 .…”

Section: Introductionmentioning

confidence: 89%

A solar cycle clock for extreme space weather

Chapman,

Dudok de Wit

2024

Sci Rep

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The variable solar cycle of activity is a long-standing problem in physics. It modulates the overall level of space weather activity at earth, which in turn can have significant societal impact. The Hilbert transform of the sunspot number is used to map the variable length, approximately 11 year Schwabe cycle onto a uniform clock. The clock is used to correlate extreme space weather seen in the aa index, the longest continuous geomagnetic record at earth, with the record of solar active region areas and latitudes since 1874. This shows that a clear switch-off of the most extreme space weather events occurs when $$>90$$ > 90 % of solar active region areas have moved to within about 15° of the solar equator, from regions of high gradient in solar differential rotation which can power coronal mass ejections, to a region where solar differential rotation is almost constant with latitude. More moderate space weather events which coincide with 27 day solar rotation recurrences in the aa index, consistent with stable, persistent source regions of high speed streams, commence when the centroid of solar active region areas moves to within 15° of the solar equator. This offers a physical explanation for the longstanding identification of a two component cycle of activity in the aa index.

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“…Storm occurrence rates and intensities vary with the approximately 11 years cycle of solar activity (Bergin et al., 2022; Chapman, McIntosh, et al., 2020) and each cycle is unique in amplitude and duration. Statistical studies to quantify space weather risk thus require observations spanning multiple solar cycles.…”

Section: Introductionmentioning

confidence: 99%

Extreme Event Statistics in Dst, SYM‐H, and SMR Geomagnetic Indices

et al. 2023

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Severe geomagnetic storms can give rise to widespread societal, economic, and technological disruption (Hapgood et al., 2021). Rare events, such as the 1859 Carrington storm (Cliver & Dietrich, 2013), and the 1921 storm (Hapgood, 2019 have been estimated to potentially result in nationwide disruption of power distribution (Oughton et al., 2017) or significant satellite loss (Horne et al., 2013). Consequently, long-term forecasting of magnetospheric space weather is of significant operational interest (Morley, 2020). A key element of an extreme space weather event is a dramatic and rapid enhancement of the large scale currents carried by the ionosphere and magnetosphere. This perturbs the magnetic field at the surface of the earth. Ground-based magnetometer observations, spanning multiple solar cycles, form the basis of geomagnetic indices which are routinely used

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Variation of Geomagnetic Index Empirical Distribution and Burst Statistics Across Successive Solar Cycles

Cited by 7 publications

References 62 publications

Newcomb-Benford Law characterization of solar wind magnetic field and geomagnetic indices

Newcomb-Benford Law characterization of solar wind magnetic field and geomagnetic indices

A solar cycle clock for extreme space weather

Extreme Event Statistics in Dst, SYM‐H, and SMR Geomagnetic Indices

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