Solar cycle 24

Solar cycle 24 is the most recently completed solar cycle, the 24th since 1755, when extensive recording of solar sunspot activity began.Kane, R.P. (2026).Some Implications Using the Group Sunspot Number Reconstruction". Solar Physics 205(2), 383-401. It began in December 2008 with a minimum smoothed sunspot number of 2.2,SIDC formula and ended in December 2019. Activity was minimal until early 2010. It reached its maximum in April 2014 with a 23 months smoothed sunspot number of 81.8. This maximum value was substantially lower than other recent solar cycles, down to a level which had not been seen since cycles 12 to 15 (1878-1923).

Predictions Prior to the minimum between the end of Solar Cycle 23 and the beginning of Solar Cycle 24, two theories predicted how strong Solar Cycle 24 would be. One camp postulated that the Sun retained a long memory (Solar Cycle 24 would be active) while the other asserted that it had a short memory (quiet). Prior to 2006, the difference was substantial with a minority of researchers predicting "the smallest solar cycle in 100 years." Another group of researchers, including one at NASA, predicted that it "looks like its going to be one of the most intense cycles since record-keeping began almost 400 years ago."

The delayed onset of high latitude spots indicating the start of Solar Cycle 24 led the "active cycle" researchers to revise their predictions downward and the consensus by 2007 was split 5-4 in favor of a smaller cycle. By 2012, consensus was a small cycle, as solar cycles are much more predictable 3 years after minima.

In May 2009 the NOAA Space Weather Prediction Center's Solar Cycle 24 Prediction Panel predicted the cycle to peak at 90 sunspots in May 2013. In May 2012 NASA's expert David Hathaway predicted a peak in Spring of 2013 with about 60 sunspots.

NASA funded and used Ken Schatten's physics-based models, which utilized a solar Dynamo model, to accurately predict the low. This method used the correlation between solar magnetic field strength at solar minimum to sunspot number at solar maximum to accurately predict the peak solar flux of each of the last three solar cycles. Schatten's predictions become accurate as early as solar minima, 5–6 years before solar max.

Results In early 2013, after several months of calm, it was obvious that the active 2011 was not a prelude to a widely predicted late 2012-early 2013 peak in solar flares, sunspots and other activity. This unexpected stage prompted some scientists to propose a "double-peaked" solar maximum, which then occurred. The first peak reached 99 in 2011 and the second peak came in early 2014 at 101.

Speculation

According to NASA, the intensity of geomagnetic storms during Solar Cycle 24 may be elevated in some areas where the Earth's magnetic field is weaker than expected. This fact was discovered by the THEMIS spacecraft in 2008. A 20-fold increase in particle counts that penetrate the Earth's magnetic field may be expected. Solar Cycle 24 has been the subject of various hypotheses and commentary pertaining to its potential effects on Earth.

While acknowledging that the next solar maximum will not necessarily produce unusual geomagnetic activity, astrophysicist Michio Kaku took advantage of the media focus on the 2012 phenomenon to draw attention to the need to develop strategies for coping with the terrestrial damage that such an event could inflict. He asserted that governments should ensure the integrity of electrical infrastructure, so as to prevent a recurrence of disruption akin to that caused by the solar storm of 1859.

The current solar cycle is currently the subject of research, as it is not generating sunspots in the expected manner. Sunspots did not begin to appear immediately after the last minimum (in 2008) and although they started to reappear in late 2009, they were at significantly lower rates than anticipated.

On April 19, 2012, the National Astronomical Observatory of Japan predicted that the Sun's magnetic field would assume a quadrupole configuration.

Throughout 2012, NASA posted news releases discrediting the 2012 phenomenon and the so-called Mayan prophecy, delinking them from solar activity and space weather.

Events +Solar flares by year

The strongest flares of Solar Cycle 24 (above M5.0 class) and related events Class Year Date Sunspot region Radio B. SR Storm CME GM Storm X9.33 2017 Sep 6 2673 R3 S1 Yes - X8.2 2017 Sep 10 2673 R3 S3 Yes - X6.9 2011 Aug 9 1263 R3 S1 Yes - X5.4 2012 Mar 7 1429 R3 S3 Yes G3 X4.9 2014 Feb 25 1990 R3 S1 Yes G2 X3.3 2013 Nov 5 1890 R3 - Yes - X3.2 2013 May 14 1748 R3 - Yes - X3.19 2014 Oct 24 2192 R3 - No - X2.8 2013 May 13 1748 R3 - Yes - X2.74 2015 May 5 2339 R3 - Yes - X2.3 2013 Oct 29 1875 R3 - Yes - X2.2 2011 Feb 15 1158 R3 - Yes G1 X2.2 2014 Jun 10 2087 R3 - ? - X2.2 2015 Mar 11 2297 R3 - Yes - X2.2 2017 Sep 6 2673 R3 - ? - X2.1 2013 Oct 25 1882 R3 - Yes - X2.1 2011 Sep 6 1283 R3 S1 Yes G3 X2.0 2014 Oct 26 2192 R3 - No - X2.0 2014 Oct 27 2192 R3 - No - X1.9 2011 Nov 3 1339 R3 - Yes - X1.9 2011 Sep 24 1302 R3 S1 Yes G4 X1.8 2011 Sep 7 1283 R3 S1 Yes G1 X1.8 2012 Oct 23 1598 R3 - No - X1.8 2014 Dec 20 2242 R3 - Yes - X1.7 2013 Oct 25 1882 R3 - Yes - X1.7 2012 Jan 27 1402 R3 S2 Yes - X1.7 2013 May 13 1748 R3 - Yes - X1.66 2014 Sep 10 2158 R3 S2 Yes G3 X1.6 2014 Oct 22 2192 R3 - No - X1.5 2011 Mar 9 1166 R3 - Yes G2 X1.5 2014 Jun 10 2087 R3 - ? - X1.4 2011 Sep 22 1302 R3 - Yes - X1.4 2012 Jul 12 1520 R3 S1 Yes G2 X1.3 2012 Mar 7 1430 R3 S3 No - X1.3 2014 Apr 25 2035 R3 - ? - X1.3 2017 Sep 7 2673 R3 S2 No G4 X1.2 2014 Jan 7 1944 R3 S2 Yes - X1.2 2013 May 15 1748 R3 S1 Yes G1 X1.1 2012 Mar 5 1429 R3 - Yes G2 X1.1 2012 Jul 6 1515 R3 S1 Yes G1 X1.1 2013 Nov 8 1890 R3 - Yes - X1.1 2013 Nov 10 1890 R3 - Yes - X1.1 2014 Oct 19 2192 R3 - No - X1.0 2013 Nov 19 1893 R3 S1 Yes - X1.0 2013 Oct 28 1875 R3 S1 Yes - X1.0 2014 Mar 29 2017 R3 - ? - X1.0 2014 Jun 11 2087 R3 - ? - X1.0 2014 Oct 25 2192 R3 - No - M9.9 2014 Jan 1 1936 R2 - Yes - M9.3 2013 Oct 24 1877 R2 - Yes - M9.3 2011 Aug 4 1261 R2 S1 Yes G4 M9.3 2011 Jul 30 1260 R2 - No - M9.3 2014 Mar 12 1996 R2 - ? - M9.2 2015 Mar 7 2339 R2 - Yes - M9.0 2012 Oct 20 1598 R2 - Yes - M8.7 2012 Jan 23 1402 R2 S3 Yes G1 M8.7 2014 Oct 22 2192 R2 - No - M8.7 2014 Dec 17 2242 R2 - Yes - M8.4 2012 Mar 10 1429 R2 - Yes - M8.3 2010 Feb 12 1046 R2 - Yes - M8.2 2015 Mar 3 2290 R2 - Yes - M8.1 2017 Sep 8 2673 R2 - ? - M7.9 2012 Mar 13 1429 R2 S2 Yes G2 M7.9 2014 Nov 5 2205 R2 - Yes - M7.9 2015 Jun 25 2371 R2 S1 Yes G2 M7.7 2012 Jul 19 1520 R2 - Yes - M7.6 2015 Sep 28 2422 R2 - ? - M7.6 2016 Jul 23 2567 R2 - Yes - M7.4 2011 Sep 25 1302 R2 - Yes G1 M7.3 2014 Apr 18 2036 R2 S1 ? - M7.3 2014 Oct 2 2173 R2 - Yes - M7.3 2017 Sep 7 2673 R2 - ? - M7.2 2014 Jan 7 1944 R2 - No - M7.1 2011 Sep 24 1302 R2 - Yes G4 M7.1 2014 Oct 27 2192 R2 - ? - M6.9 2012 Jul 8 1515 R2 S1 Yes - M6.9 2014 Dec 18 2241 R2 - Yes M6.7 2011 Sep 8 1283 R2 - Yes G1 M6.7 2014 Oct 27 2192 R2 - ? - M6.7 2016 Apr 18 2529 R2 - Yes - M6.6 2011 Feb 13 1158 R2 - Yes - M6.6 2011 Feb 18 1158 R2 - No - M6.6 2014 Jan 30 1967 R2 - Yes - M6.6 2014 Oct 28 2192 R2 - ? - M6.6 2015 Jun 22 2371 R2 S2 Yes G4 M6.5 2013 Apr 11 1719 R2 S2 Yes - M6.5 2014 Apr 2 2027 R2 - ? - M6.5 2014 Jul 8 2113 R2 - ? - M6.5 2014 Nov 3 2205 R2 S1 Yes - M6.4 2010 Feb 7 1045 R2 - Yes - M6.4 2013 Dec 31 1936 R2 - Yes - M6.3 2013 Nov 1 1884 R2 - Yes - M6.3 2012 Mar 9 1429 R2 - Yes G2 M6.1 2012 Jul 5 1515 R2 - No - M6.1 2012 Jul 28 1532 R2 - Yes - M6.1 2014 Dec 4 2222 R2 - Yes - M6.0 2012 Nov 13 1613 R2 - Yes - M6.0 2011 Aug 3 1261 R2 - Yes G4 M5.9 2013 Jun 7 1762 R2 - Yes - M5.9 2014 Aug 24 2151 R2 - ? - M5.8 2011 Sep 24 1302 R2 - ? - M5.8 2015 Mar 9 2297 R2 - Yes - M5.7 2012 May 10 1476 R2 - Yes - M5.7 2013 May 3 1739 R2 - Yes - M5.7 2014 Nov 16 2209 R2 - ? - M5.7 2017 Apr 2 2644 R2 - No - M5.6 2012 Jul 2 1515 R2 - Yes - M5.6 2015 Jan 13 2257 R2 - No - M5.6 2015 Aug 24 2403 R2 - ? - M5.5 2012 Aug 18 1548 R2 - No - M5.5 2015 Oct 2 2422 R2 - ? - M5.5 2016 Jul 23 2567 R2 - Yes - M5.5 2017 Sep 4 2673 R2 - ? - M5.4 2010 Nov 6 1121 R2 - ? - M5.4 2014 Nov 6 2205 R2 - ? - M5.3 2011 Sep 6 1283 R2 - Yes G3 M5.3 2011 Mar 8 1165 R2 - Yes G1 M5.3 2012 Jul 4 1515 R2 - Yes - M5.3 2014 May 8 2056 R2 - ? G1 M5.3 2017 Apr 2 2644 R2 - No - M5.2 2014 Feb 4 1967 R2 - ? - M5.1 2012 May 17 1476 R2 S2 Yes - M5.1 2013 Oct 28 1875 R2 - Yes - M5.1 2014 Sep 28 2173 R2 - Yes - M5.1 2015 Mar 10 2297 R2 - Yes -Source: Solarham.com and NOAA's SWPC. The CME field indicates whether the solar flare hurled a CME (oriented or not to Earth). The Radio B./SR Storm/GM Storm fields indicate the NOAA scales of radio blackouts/solar radiation storms/geomagnetic storms, being G1 (minor), G2 (moderate), G3 (strong), G4 (severe) and G5 (extreme).

2008 +Solar flares in 2008

On 4 January 2008, an active region appeared with magnetic polarity reversed compared to that expected by Hale's law for solar cycle 23. This presaged the start of solar cycle 24—though did not mark its official beginning. The region was located at the relatively high latitude 30° N which, according to Spörer's law, provided further evidence for the arrival of cycle 24. The NOAA assigned it the active region number AR10981.

Only a few sunspots were observed on the surface of the Sun throughout 2008. The smoothed monthly sunspot number reached a minimum of 2.2 in December 2008, therefore an international panel of scientists declared that month as solar minimum and the beginning of Solar Cycle 24.

2009 +Solar flares in 2009

Solar activity remained extremely low throughout 2009. The observed monthly sunspots exceeded 10 only in December.

2010 +Solar flares in 2010

On 19 January 2010, active region AR11041 produced an M2.3-class flare, the first flare of cycle 24 above M-class. It was followed by an M1.7-class flare seven hours later and four consecutive M-class flares the next day. Among the four flares, the strongest reached a strength of M3.4.

On 12 February 2010, active region AR11046 produced an M8.3-class flare. Later in the month, active regions AR11045 and AR11046 unleashed a total of nine M-class flares.

On 5 April 2010, the first coronal mass ejection (CME) of cycle 24 erupted at an active region causing a G3 (strong) geomagnetic storm on Earth. The Kp index, which quantifies disturbances in the horizontal component of Earth's magnetic field, reached a value of 7.

On 1 and 2 August 2010, a series of four large CMEs were observed erupting from the Sun's Earth-facing side. These CMEs were likely connected to a C3.2-class flare from active region AR11092 despite the CMEs taking place about 400,000 km apart from the region. On 4 August 2010, a G2 (moderate) geomagnetic storm caused aurorae to be visible in the northern hemisphere at latitudes as far south as 45° N near Michigan and Wisconsin in the United States, and Ontario, Canada. European observers reported sightings as far south as Denmark near latitude 56° N. The aurorae were reportedly green in color due to the interaction of the solar particles with oxygen atoms in the relatively denser atmosphere of southern latitudes.

On 14 August 2010, a C4.4-class flare produced the first solar radiation storm of cycle 24. The proton storm event was minor, rating at S1, and was easily absorbed by the Earth's ionosphere.

On 6 November 2010, active region AR11121 emitted an M5.4 flare.

2011 +Solar flares in 2011

February

'Valentine’s Day' 2011 flare