Comparison of Latitude Distribution and Evolution of Even and Odd Sunspot Cycles

Takalo, Jouni

doi:10.1007/s11207-020-01615-1

Cited by 11 publications

(4 citation statements)

References 28 publications

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“…We calculated, using two-sided T-test for unequal means (see the T-test method in Takalo, 2020a andMursula, 2020), that the significance of the decline (average Dst is −12.7) for the raw (unsmoothed) Dst-index is 99% for even cycles (SC20 and SC22) with p < 10 −15 compared to nine months earlier (average Dst −23.8) and nine months after the marked interval (average Dst −23.6). For odd cycles (SC21 and SC23) the decline between 1322 -1527 is −11.9 on the average with p = 3 × 10 −5 compared to eight months earlier (average Dst −17.3) and p = 9 × 10 −9 compared to eight months after the marked interval (average Dst is −19.5).…”

Section: Dst Dxt and DCX During Solar Cycles 17 -23mentioning

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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Section: Dst Dxt and DCX During Solar Cycles 17 -23mentioning

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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“…It is evident that the absolute values of the maxima are all between 15 -20 degrees of heliographic latitude. These latitudes are somewhat larger than the maxima of the sunspot distributions, which are between 14.9 and 15.5 for even and odd cycles, respectively (Takalo, 2020a). The overall values of the corona are slightly stronger for northern hemisphere than the southern hemisphere.…”

Section: Homogeneous Coronal Data Setmentioning

confidence: 80%

Spatial and Temporal Distribution of Solar Green Line Corona for Solar Cycles 18-24

Takalo

2022

Preprint

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Homogeneous coronal data set (HCDS) of the green corona (Fe XIV) and coronal index of the solar activity (CI) have been used to study timelatitudinal distribution in solar cycles 18 -24 and compared with similar distribution of sunspots, the magnetic fields and the solar radio flux 10.7 cm. The most important results are: (a) distribution of coronal intensities related to the cycle maximum are different for individual cycles, (b) the poleward migration of the HCDS from mid latitudes in each cycle exists, even in extremely weak Cycle 24, and the same is valid for the equatorward migration (c) the overall values of HCDS are slightly stronger for the northern hemisphere than for the southern one, (d) distribution of the HDCS are in coincidence with strongest photospheric magnetic fields (B>50 Gauss) and histogram of the sunspot groups, (e) Gnevyshev gap was confirmed with at least 95 % confidence in the CI, however, with different behavior for odd and even cycles. Principal component analysis (PCA) showed that the first and second component account for 87.7 % and 7.3 % of the total variation of the CI. Furthermore, the PC2 of the green corona was quite different for cycle 21, compared with other cycles.

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“…There is, however, difference in the northern hemisphere such that small area SGs are located at slightly higher latitudes in the ascending phase and at lower latitudes in the descending phase of the average cycle. This is because the large area SGs are spread mainly between latitudes 10 -25 degrees, but small area SGs more widely between 0 -40 degrees (Takalo, 2020a). In the southern hemisphere the drift paths are, however, more similar.…”

Section: Resultsmentioning

confidence: 95%

The latitudinal migration of the sunspot groups

Takalo

2024

Preprint

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We analyse the monthly sunspot group (SG) data for Solar Cycles C8 - C23 and calculate the average latitude of the drift path for the northern and southern hemisphere of the Sun. We find that exponential function fits slightly better than the second-order polynomial to the average drift of the SGs. The drift velocities are are 0.30 and 0.27 degrees/month (meridional speed approximately 1.41 and 1.27 m/s) in the beginning and 0.071 and 0.069 degrees/month (approximately 0.33 and 0.32 m/s) at the end of the average cycle for northern and southern hemisphere, respectively. We do also bi-linear fits (first-order polynomial fits in two fractions), because they tell us the crossing point were the drift velocity changes the most. This crossing point for the Cycles C8 - C23 is at 50 months and 15.4 degrees of latitude for the northern hemisphere and 54 months and -14.4 degrees for the southern hemisphere. The drift velocities calculated from the slopes of the bi-linear fits are 0.233 and 0.216 degrees/month (approximately 1.10 and 1.02 m/s) before the crossing point and 0.118 and 0.101 degrees/month (approximately 0.55 and 0.47 m/s) after the crossing point. We find a slight dependence of the migration on the strength of the cycle such that the drift path of the stronger cycles follow slightly higher latitudes than those of the weaker cycles. The areas of the sunspot groups affect also slightly to the drift path such that large area SGs have path at somewhat lower latitudes in the ascending phase and higher latitudes in the descending phase of the cycle than the smaller area SGs.

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Comparison of Latitude Distribution and Evolution of Even and Odd Sunspot Cycles

Cited by 11 publications

References 28 publications

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

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

Spatial and Temporal Distribution of Solar Green Line Corona for Solar Cycles 18-24

The latitudinal migration of the sunspot groups

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