Evolution of Solar and Geomagnetic Activity Indices, and Their Relationship: 1960 – 2001

Verbanac, Giuliana; Mandea, Mioara; Vršnak, Bojan; Sentić, Stipo

doi:10.1007/s11207-011-9801-y

Cited by 18 publications

(18 citation statements)

References 40 publications

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“…A good correspondence between the aa index and the number of days per year with a solar wind speed higher than 500 km s −1 has been reported (Echer et al, 2004). Verbanac et al (2011) noted that the evolution of the Ap and Dst (sensitive to storm-time disturbances) indices correlates best with the interplanetary magnetic field (IMF) variations, which strongly affect the ring current evolution (Echer et al, 2008).…”

Section: Discussionmentioning

confidence: 84%

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Latitude dependence of long-term geomagnetic activity and its solar wind drivers

2015

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Abstract.To validate the usage of global indices in studies of geomagnetic activity, we have examined the latitude dependence of geomagnetic variations in Fennoscandia and Svalbard from 1994 to 2010. Daily standard deviation (SD) values of the horizontal magnetic field have been used as a measure of the ground magnetic disturbance level. We found that the timing of the geomagnetic minimum depends on the latitude region: corresponding to the minimum of sunspot cycle 22 (in 1996), the geomagnetic minimum occurred between the geomagnetic latitudes 57-61 • in 1996 and at the latitudes 64-67 • in 1997, which are the average auroral oval latitudes. During sunspot cycle 23, all latitude regions experienced the minimum in 2009, a year after the sunspot minimum. These timing differences are due to the latitude dependence of the 10 s daily SD on the different solar wind drivers. In the latitude region of 64-67 • , the impact of the high-speed solar wind streams (HSSs) on the geomagnetic activity is the most pronounced compared to the other latitude groups, while in the latitude region of 57-61 • , the importance of the coronal mass ejections (CMEs) dominates. The geomagnetic activity maxima during ascending solar cycle phases are typically caused by CME activity and occur especially in the oval and sub-auroral regions. The strongest geomagnetic activity occurs during the descending solar cycle phases due to a mixture of CME and HSS activity. Closer to the solar minimum, less severe geomagnetic activity is driven by HSSs and mainly visible in the poleward part of the auroral region. According to our study, however, the timing of the geomagnetic activity minima (and maxima) in different latitude bands is different, due to the relative importance of different solar wind drivers at different latitudes.

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Section: Discussionmentioning

confidence: 84%

“…For example, aa and Ap indices have been found to correlate with the sunspot number with roughly a 2-year time lag (Echer et al, 2004;Verbanac et al, 2011). A good correspondence between the aa index and the number of days per year with a solar wind speed higher than 500 km s −1 has been reported (Echer et al, 2004).…”

Section: Discussionmentioning

confidence: 88%

Latitude dependence of long-term geomagnetic activity and its solar wind drivers

2015

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“…Takalo and Mursula (2020) and Takalo (2020b) have also shown that the larger the sunspot groups the more clearly their overall distribution during the solar cycle is double-peaked. Verbanac et al (2011) analyzed the correlation (during 1960 -2001) of several solaractivity indices: sunspot number, group sunspot number, cumulative sunspot area, solar radio flux F 10.7 , and interplanetary magnetic field strength (IMF) with geomagnetic activity indices: Ap, Dst, and Dcx, and the regional geomagnetic index RES, specifically estimated for the European region. The geomagnetic indices Ap, Dcx, Dst, and RES are all well correlated with the considered solar indices.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Geomagnetic Indices During Even and Odd Solar Cycles SC17 – SC24: Signatures of Gnevyshev Gap in Geomagnetic Activity

Takalo

2021

Sol Phys

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We show that the time series of sunspot group areas has a gap, the so-called Gnevyshev gap (GG), between ascending and descending phases of the cycle and especially so for the even-numbered cycles. For the odd cycles this gap is less obvious, and is only a small decline after the maximum of the cycle. We resample the cycles to have the same length of 3945 days (about 10.8 years), and show that the decline is between 1445 – 1567 days after the start of the cycle for the even cycles, and extending sometimes until 1725 days from the start of the cycle. For the odd cycles the gap is a little earlier, 1332 – 1445 days after the start of the cycles with no extension. We analyze geomagnetic disturbances for Solar Cycles 17 – 24 using the Dst-index, the related Dxt- and Dcx-indices, and the Ap-index. In all of these time series there is a decline at the time, or somewhat after, the GG in the solar indices, and it is at its deepest between 1567 – 1725 days for the even cycles and between 1445 – 1567 days for the odd cycles. The averages of these indices for even cycles in the interval 1445 – 1725 are 46%, 46%, 18%, and 29% smaller compared to surrounding intervals of similar length for Dst, Dxt, Dcx, and Ap, respectively. For odd cycles the averages of the Dst- and Dxt-indices between 1322 – 1567 days are 31% and 12% smaller than the surrounding intervals, but not smaller for the Dcx-index and only 4% smaller for the Ap-index. The declines are significant at the 99% level for both even and odd cycles of the Dst-index and for the Dxt-, Dcx- and Ap-indices for even cycles. For odd cycles of the Dxt-index the significance is 95%, but the decline is insignificant for odd cycles of the Dcx- and Ap-indices.

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“…Ref. [11] analyzed correlations between yearly mean solar indices (sunspot number, group sunspot number, and cumulative sunspot area) and geomagnetic indices (Ap and Dst) between 1960 and 2001. They reported the correlation coefficient of sunspot numbers with Ap and Dst as follows: 0.55 with a time delay of 2 years, and -0.59 with no delay, successively.…”

Section: Resultsmentioning

confidence: 99%

Total sunspot number calculation based on flare production potential of sunspotgroups: reconstruction of SSN and its relation to some geomagnetic indices

Karslioğlu¹,

Dönmez²,

Kılçık³

2019

Turk J Phys

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In this study, we modified the previously introduced X-ray flare production potential (FPP) of each modified Zurich sunspot group based on its X-ray flare peak flux. Then, using these FPPs, the daily total sunspot number (Zurich number) calculation equation was modified; thus, new sunspot number data (CRz) were produced. We also compared ISSN and CRz with some geomagnetic indices (Dst, the maximum CME speed, and Ap indices). We found that the CRz data describe the geomagnetic indices quite well compared to ISSN. By using the regression equation between CRz and the sunspot area, the CRz dataset was recalculated back to 1874. Those reconstructed datasets were compared to observational data, and it was found that reconstructed and observed monthly datasets show very good agreement. The only small differences exist in maxima and minima of cycles.

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Evolution of Solar and Geomagnetic Activity Indices, and Their Relationship: 1960 – 2001

Cited by 18 publications

References 40 publications

Latitude dependence of long-term geomagnetic activity and its solar wind drivers

Latitude dependence of long-term geomagnetic activity and its solar wind drivers

Comparison of Geomagnetic Indices During Even and Odd Solar Cycles SC17 – SC24: Signatures of Gnevyshev Gap in Geomagnetic Activity

Total sunspot number calculation based on flare production potential of sunspotgroups: reconstruction of SSN and its relation to some geomagnetic indices

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