On the periodic variations of geomagnetic activity indices Ap and ap

Schreiber, Hermann

doi:10.1007/s00585-998-0510-2

Cited by 22 publications

(9 citation statements)

References 30 publications

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“…The 27 days window is in agreement with the solar rotation period, which has a significant impact on the VTEC variation of ionosphere (Bremer et al., 2006; Schmölter et al., 2021). Both the 27 days variation of solar radiation and the 27 days variation of geomagnetic activity caused by the solar wind and interplanetary magnetic field, have effects on ionospheric VTEC (Ma et al., 2012; Schreiber, 1998). The window size smaller and larger than 27 days is more affected by the daily variations and the seasonal variations (Nishioka et al., 2017).…”

Section: Data and Methodology For Isugmentioning

confidence: 99%

Ionospheric Storm Scale Index Based on High Time Resolution UPC‐IonSAT Global Ionospheric Maps (IsUG)

et al. 2021

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Driven by the high energy inputs resulting from geomagnetic storms, the ionospheric storms contain varying electron density and have significant impacts on the society in general and on the space environment in particular, including high ionospheric correction error for trans-ionospheric radio signals, blackouts of High Frequency (HF) communication systems and disruption of Ultra High Frequency (UHF) satellite communications (Buonsanto, 1999). The evolution of ionospheric storms can be divided into positive phase (when the electron density increases) and negative phase (when the electron density decreases; Fagundes et al., 2016). It is important to identify the ionospheric conditions for the space weather warnings to mitigate the influence of ionospheric storms.In 1960, a monthly ionospheric index was introduced in terms of a monthly mean of the ionospheric critical frequency 𝐴𝐴 𝐴𝐴0𝐹𝐹 2 measured from several stations, reflecting the average conditions of the ionosphere (Minnis & Bazzard, 1960). And the improved ionospheric index MF2 was proposed to increase the accuracy of monthly median 𝐴𝐴 𝐴𝐴0𝐹𝐹 2 estimation and long-term prediction (Mikhailov & Mikhailov, 1995; Perrone & De

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Section: Data and Methodology For Isugmentioning

confidence: 99%

Ionospheric Storm Scale Index Based on High Time Resolution UPC‐IonSAT Global Ionospheric Maps (IsUG)

et al. 2021

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“…periodicities between 2-512 days, during the period 2013-2018 using the wavelet analysis. The fact that several different phenomena can contribute to different periodicities and these are not constant in time could make Fourier analysis unsuitable (Schreiber et al 1998) and therefore it has been used wavelet analysis to observe the intrinsic temporal variation in the periods.…”

Section: Data Analysis and Methodsmentioning

confidence: 99%

Short-Term Periodicities Observed in Neutron Monitor Counting Rates

López-Comazzi

Blanco

2020

Sol Phys

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The main objective is to check whether the periodicities observed in the cosmic rays in the interval 2013-2018 are affected by the magnetic rigidity or the height at which the neutron monitors are placed. A Global Neutron Monitor (GNM) has been defined as representative of the neutron monitor global network. The Morlet wavelet analysis is applied to the GNM and the selected solar activity parameters to find out common periodicities. Short-term periodicities of 13.5, 27, 48, 92, 132 and 298 days have been observed in cosmic ray intensity. A clear inverse relationship between rigidity and spectral power has been obtained for the 13.5, 48, 92, 132-day periods. A not so clear but still observed direct relationship between the height of the neutron monitors and the spectral power for the 48, 92, 132-day periods has been also found. The periodicity of 92 days is the one which shows the highest dependence with rigidity cutoff and height. As far as we know, this is the first time that these dependencies are reported. We think that these observations could be explained by assuming some cosmic ray intensity energy dependence in such periodicities and a competitive effect between rigidity and height.

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“…The lifetime of solar active regions and CIRs can last longer than one solar rotation period. These recurrent variations in solar wind and IMF produce periodic geomagnetic activity of ∼27 days when solar wind and IMF interact with the magnetosphere [ Schreiber , 1998; Parker , 2005].…”

Section: Introductionmentioning

confidence: 99%

The effect of ∼27 day solar rotation on ionospheric F₂ region peak densities (N_mF₂)

Ma¹,

Xu²,

Wang³

et al. 2012

J. Geophys. Res.

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[1] Ionospheric F 2 region peak electron densities (N m F 2 ) observed from 11 ionosonde stations in the East Asian-Australian sector from 1969 to 1986 have been used to investigate the effect of $27 day solar rotation on the ionosphere. These stations were located from the magnetically equatorial regions to the middle latitudes in both hemispheres. We found that, averaged over all stations and for 18 years, the normalized standard deviation of the midday $27 day variations of N m F 2 was 8% and that of the midnight variations was 10%. We applied different data analysis methods, including Fourier transform, band-pass filter, and multiple linear regression analysis, to determine quantitatively the sources of the observed $27 day variations of N m F 2 and their relative contributions to these variations. Our results show that the $27 day variations in solar radiation and geomagnetic activity, caused by solar rotation, are the main drivers of the ionospheric $27 day variations. They accounted for more than 85% of the variations seen in the N m F 2 $27 day variation, and their contributions became about 95% at higher latitudes. At geomagnetically low latitudes, the contribution of the $27 day variation in solar EUV radiation was greater than that of the $27 day variation in geomagnetic activity. However, the contribution from geomagnetic activity became more significant and was even larger than the contribution of solar radiation at higher latitudes, especially at midnight. At all latitudes the correlation between the $27 day variations of N m F 2 and solar radiation was evidently positive, whereas that between N m F 2 and geomagnetic activity was positive at geomagnetically low latitudes and became negative at higher middle latitudes. We did not found large seasonal or solar cycle changes in the $27 day variations of N m F 2 . These variations, however, did show significant differences between the two hemispheres.

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On the periodic variations of geomagnetic activity indices Ap and ap

Cited by 22 publications

References 30 publications

Ionospheric Storm Scale Index Based on High Time Resolution UPC‐IonSAT Global Ionospheric Maps (IsUG)

Ionospheric Storm Scale Index Based on High Time Resolution UPC‐IonSAT Global Ionospheric Maps (IsUG)

Short-Term Periodicities Observed in Neutron Monitor Counting Rates

The effect of ∼27 day solar rotation on ionospheric F₂ region peak densities (N_mF₂)

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On the periodic variations of geomagnetic activity indices Ap and ap

Cited by 22 publications

References 30 publications

Ionospheric Storm Scale Index Based on High Time Resolution UPC‐IonSAT Global Ionospheric Maps (IsUG)

Ionospheric Storm Scale Index Based on High Time Resolution UPC‐IonSAT Global Ionospheric Maps (IsUG)

Short-Term Periodicities Observed in Neutron Monitor Counting Rates

The effect of ∼27 day solar rotation on ionospheric F2 region peak densities (NmF2)

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The effect of ∼27 day solar rotation on ionospheric F₂ region peak densities (N_mF₂)