Solar maximum
Solar maximum is the regular period of greatest solar activity during the Sun's 11-year solar cycle. During solar maximum, large numbers of sunspots appear, and the solar irradiance output grows by about 0.07%.[2] On average, the solar cycle takes about 11 years to go from one solar maximum to the next, with duration observed varying from 9 to 14 years.
Large solar storms often occur during solar maximum. For example, the Carrington Event, which took place a few months before the solar maximum of solar cycle 10, was the most intense geomagnetic storm in recorded history and widely considered to have been caused by an equally large solar storm.[3]
Predictions
[edit]Predictions of a future maximum's timing and strength are very difficult; predictions vary widely. There was a solar maximum in 2000. In 2006, NASA initially expected a solar maximum in 2010 or 2011, and thought that it could be the strongest since 1958.[4] However, the solar maximum was not declared to have occurred until 2014, and even then was ranked among the weakest on record.[5]
Another index of solar activity allowing predicting solar cycles on a larger timescale tan once cycle was carried out using Principle Component Analysis (PCA) (Zharkova et al, 2015) by calculating eigen vectors (EVs) of solar background magnetic field (SBMF)using magnetic synoptic maps of Wilcox Solar Observatory (Stanford, US) for cycle 21-23 (Zharkova et al, 2015 https://www.nature.com/articles/srep15689) and 21-24 (Zharkova and Shepherd, 2022 https://solargsm.com/wp-content/uploads/2022/04/zharkova_shepherd_mnras22.pdf.
The first two PCs, or EVs, derived from PCA reflect the two primary waves of the solar magnetic dynamo produced by dipole magnetic sources (Zharkova et al. 2015) as shown in their Figure 1 for cycles 21-26 and Figure 3 for 2000 thousand years (1200-3200).
The authors derived the analytical formula for these two magnetic waves (eigen vector) and managed to reproduced with this formula the vast majority of sunspot cycles in the past as shown in Figures 6 and 9. The comparison of sunspot and modulus summary curves of two eigen vectors with scatter plots shown high 67% correlation (Figure 8) with sunspot numbers for the cycles from 1900 to 2020 shown in the paper Zharkova et al, 2023a https://solargsm.com/wp-content/uploads/2023/04/zharkova_etal_mnras2023.pdf.
Furthermore, the inclusion of a second set of PCs, or magnetic waves, produced by quadruple magnetic waves (Zharkova and Shepherd, 2022) revealed the their summary curve fit very well the soft X-ray index of solar flares for cycles 21-24. Hence the joint effect of dipole, quadruple, octuple and sextuple summary curves can cover a wider range of solar activity indices including flares and active regions.
Grand solar minima and maxima
[edit]In addition to the ~11 year solar cycle, the intensity of the solar maxima can vary from cycle to cycle. When several solar cycles exhibit greater than average activity for decades or centuries, this period is labelled "Grand solar maximum". Solar cycles still occur during these grand solar maximum periods, but the intensity of those cycles is greater. Likewise, extended periods in which the solar maximum is lower than average are labeled "grand solar minima". Some researchers suggest that grand solar maxima have shown some correlation with global and regional climate changes, although others dispute this hypothesis (e.g., see Medieval Warm Period).
Following the advent of telescopic solar observation with Galileo's 1611 observations, the intensity of solar maxima is typically measured by counting numbers and size of sunspots; for periods previous to this, isotope ratios in ice cores can be used to estimate solar activity. The table below shows the approximate dates of some of the proposed solar minima in historical times.
Also besides the sunspot index there is another index of solar activity - the summary curve of two eigen vectors, or two principal components (PCs), derived with Principle Components Analysis, from the full disk magnetograms of solar background magnetic field in Zharkova et al, 2015 https://www.nature.com/articles/srep15689), presents the solar activity backward 1200 years and forward to 3200 years.
This curve reveals the very distinct periodic variations of the 11y cycle amplitudes in every 330–380 yr, or Grand Solar Cycles (GSCs) (see Figure 3 in Zharkova et al, 2015). These GSCs are separated by the Grand Solar Minima (GSMs) when the 11 yr cycle amplitudes become very small, similar to those reported for Maunder, Wolf, Oort, and other GSMs. The summary curve has also shown the modern GSM to occur in the cycles 25–27, or in 2020–2053 (Zharkova et al. 2015; Zharkova 2020 https://www.tandfonline.com/doi/full/10.1080/23328940.2020.1796243).
The expansion of this summary curve of two PCs, or EVs, up to 3000 years backwards can also reveal that the summary curve hit the main GSM down to Homeric minimum about 800 BC (Fig. 1 in Zharkova et al, 2018a https://solargsm.com/wp-content/uploads/2020/03/zharkova_iau335_paper1.pdf with all the objections by Usoskin answered in Zharkova et al, 2018b https://solargsm.com/wp-content/uploads/2020/03/zharkova_reply2usoskin_jastp17.pdf).
| Event | Start | End |
|---|---|---|
| Homeric minimum[6] | 950BC | 800BC |
| Oort minimum | 1040 | 1080 |
| Medieval maximum | 1100 | 1250 |
| Wolf minimum | 1280 | 1350 |
| Spörer Minimum | 1450 | 1550 |
| Maunder Minimum | 1645 | 1715 |
| Dalton Minimum | 1790 | 1820 |
| Modern Maximum | 1914 | 2008 |
| Unspecified | 2009 | present |
A proposed list of historical Grand minima of solar activity[7] includes also Grand minima ca. 690 AD, 360 BC, 770 BC, 1390 BC, 2860 BC, 3340 BC, 3500 BC, 3630 BC, 3940 BC, 4230 BC, 4330 BC, 5260 BC, 5460 BC, 5620 BC, 5710 BC, 5990 BC, 6220 BC, 6400 BC, 7040 BC, 7310 BC, 7520 BC, 8220 BC, 9170 BC.
See also
[edit]- Solar wind
- Solar variation
- Solar minimum
- List of solar cycles – table of solar cycles
References
[edit]- ^ NASA
- ^ C. D. Camp & K. K. Tung (2007). "Surface warming by the solar cycle as revealed by the composite mean difference projection" (PDF). Geophysical Research Letters. 34 (14): L14703. Bibcode:2007GeoRL..3414703C. doi:10.1029/2007GL030207. Retrieved 20 January 2012.
- ^ "Monster radiation burst from Sun". BBC News. 14 May 2013. Retrieved 2015-01-06.
- ^ "Solar Storm Warning", Science@NASA, 10 March 2006, Accessed 26 Mar. 2010
- ^ "Solar Mini-Max". NASA. Retrieved 2014-12-24.
- ^ Celia Martin-Puertas; Katja Matthes; Achim Brauer; Raimund Muscheler; et al. (April 2, 2012). "Regional atmospheric circulation shifts induced by a grand solar minimum". Nature Geoscience. 5 (6): 397–401. Bibcode:2012NatGe...5..397M. doi:10.1038/ngeo1460.
- ^ Usoskin, Ilya G.; Solanki, Sami K.; Kovaltsov, Gennady A. (2007). "Grand minima and maxima of solar activity: new observational constraints" (PDF). Astron. Astrophys. 471 (1): 301–9. arXiv:0706.0385. Bibcode:2007A&A...471..301U. doi:10.1051/0004-6361:20077704. S2CID 7742132.
