Solar cycle 24

ISES Solar Cycle 24 Sunspot Number Progression through January 2012

NASA Solar Cycle 24 Sunspot Number Prediction through January 2012

Solar Cycle 24 is the 24th solar cycle since 1755, when recording of solar sunspot activity began. It is the current solar cycle, and began on 8 January 2008, but there was minimal activity through early 2009. The cycle continues to fall below predictions and is currently exhibiting 70% lower sunspot activity than originally predicted in May 2009.

Predictions

NASA predicts that Solar Cycle 24 will show a peak in the smoothed sunspot number in early 2013 with about 63 sunspots. This would make it the least active cycle in the past one hundred years.

Speculation

The 2008 breach of Earth's magnetic shield

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 has taken 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 asserts that governments should ensure the integrity of electrical infrastructures, 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 does not appear to be generating sunspots in the manner which would be expected. Sunspots did not begin to appear immediately after the last minimum (in 2008) and although they started to reappear in late 2009, they are at significantly lower than anticipated.

Events

February 2010

Sunspot 1045 produced an M8.3-class flare on February 6, 2010.

August 2010 complex eruption

Multiple coronal mass ejections

On August 1, 2010, scientists at the Harvard-Smithsonian Center for Astrophysics (CfA) observed a series of four large Coronal mass ejections (CME) emanating from the Earth-facing hemisphere by analyzing images recorded at NASA's Solar Dynamics Observatory. The observed velocities of the ejecta varied between 670,560 m/s and 1,118,000 m/s (metre per second), and were expected to reach the Earth's geomagnetic field sometime between August 4 and early August 5. As of 05:00 UTC August 4, the estimated time of arrival of the series was as follows:

• Wednesday, August 4 – 07:00 UTC
• Wednesday, August 4 – 17:00 UTC
• Thursday, August 5 – 00:00 UTC
• Thursday, August 5 – 06:00 UTC

All four ejections were described as large and, according to scientists, possessed enough energy to cause aurorae to be observed by naked eye in non-polar regions. According to reports, aurorae would be visible at night toward the poleward horizon in temperate latitudes between 45° to 50°, and near overhead in regions closer to the poles. The initial coronal mass ejection of August 1 originated from a sunspot designated Sunspot 1092, which was large enough to be seen without the aid of a solar telescope. Aside from the visual effects of this CME series, scientists warned that electric impulses caused by disruptions in the magnetic field due to the ionized particles may damage infrastructure such as power grids and telephone lines not adequately protected against induced magnetic current. It has also been reported that several Earth-orbiting satellites may be in similar danger. According to Leon Golub, an astronomer at CfA:

This eruption is directed right at us and is expected to get here early in the day on August 4. It's the first major Earth-directed eruption in quite some time. When such an expulsion reaches Earth, it interacts with the planet's magnetic field and can create a geomagnetic storm. Solar particles stream down the field lines toward Earth's poles. Those particles crash with atoms of nitrogen and oxygen in the atmosphere, which then glow like little neon signs. Sky watchers in the northern U.S. and other countries should look toward the north late Tuesday or early Wednesday for rippling "curtains" of green and red light.

Solar flare

According to the Solar Dynamics Observatory, these CMEs were probably connected to a C3-class solar flare that erupted simultaneously. The origin of this blast was sunspot 1092. Connection between both events was established despite the ~400,000 km distance between them.

Aurorae observations

In the early morning hours of August 4, 2010 aurorae occurred in the northern hemisphere that were visible at latitudes as far south as Michigan and Wisconsin in the United States, and Ontario, Canada near latitude 45° North (see image at right). European observers reported sightings as far south as Denmark near latitude 56° North. 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. This, however, was only the first wave of solar wind; the third and last was expected for the evening of August 5, but missed Earth entirely.

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  Video captured by NASA's Solar Dynamics Observatory of the initial ejection taken August 1, 2010.

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  The coronal mass ejection starts at 2:36 UTC and ends at 3:56 UTC on August 1 in this animation on STEREO Ahead images.

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  Solar northern hemisphere during the first eruption as seen in extreme ultraviolet by the Solar Dynamics Observatory.

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  SDO multi-wavelength image of the August 1, 2010 event.

'Valentine’s Day' 2011 solar flare

At 01:56 UT on February 15, 2011 sunspot group 1158 produced an X2.2-class solar flare. Baptized as the Valentine's Day solar event by the scientific community, it was the first Solar Cycle 24 flare reaching X class level. In fact, it was the first of its class since December 2006. In addition to flashing Earth with UV radiation, the explosion also hurled a CME in Earth's direction. The magnetosphere was impacted on February 18. The CME struck a minor G1-level geomagnetic storm.
Shortly after, on February 18, fast-growing sunspot complex 1161-1162 erupted as well, producing an M6.6-class solar flare.

March 2011

A CME exploded from the vicinity of sunspot 1164 during the late hours of March 7, 2011. It leapt away from the Sun traveling ~2200 km/s, making it the fastest CME since September 2005.
On March 9, active region 1166 unleashed an X1.5-class solar flare.

July 2011

Sunspot 1260 produced an M9.3-class solar flare on July 30, 2011. Because of its brevity, the eruption did not hurl a substantial cloud of material toward Earth, so it was not geoeffective.

August 2011

In early August, active sunspot 1261 unleashed M class flares, with the highest being M9.3. This flare, dated on August 4, propelled a bright CME toward Earth. On the night of August 5, auroras were reported as far south as Oklahoma and Alabama. The storm also sparked a G4 (severe level) out of 5 geomagnetic storm, enough to make power outages. It was one of the strongest geomagnetic storms in years. In the southern hemisphere, auroras could have been seen as far north as South Africa, Southern Chile and Southern Australia.

X6.9-class flare

On August 9 at 0805 UT, sunspot 1263 produced a massive X6.9-class solar flare, the third X-flare of Solar Cycle 24 and the most powerful so far. Although the flare was not Earth-directed, radiation created waves of ionization in Earth's upper atmosphere, briefly disrupting communications at some VLF and HF radio frequencies.

The most powerful flares of Solar Cycle 24

Class Year Date Sunspot region X6.9 2011 August 9 1263 X2.2 2011 February 15 1158 X2.1 2011 September 6 1283 X1.9 2011 November 3 1339 X1.9 2011 September 24 1302 X1.8 2011 September 7 1283 X1.7 2012 January 27 1402 X1.5 2011 March 9 1166 X1.4 2011 September 22 1302 M9.3 2011 August 4 1261 M9.3 2011 July 30 1260 M8.7 2012 January 23 1402 M8.3 2010 February 6 1045 M6.6 2011 February 18 1158 Source: Solarham.com

September 2011

Sunspot 1283 erupted with an M5.3-class solar flare on September 6 at 01:50 UT. The eruption was Earth-directed. Just 21 hours later, an X2.1-class solar flare – some four times stronger than the earlier flare – erupted from the same sunspot region. The next day, September 7, an X1.8-class solar flare erupted from sunspot 1283. A fourth flare, an M6-class, was ejected by the same sunspot on September 8.

This sequence of flares produced waves of ionization in Earth's upper atmosphere, briefly altering the propagation of low-frequency radio signals around our planet. Moreover, the eruptions hurled clouds of plasma in our direction. CME impacts, strong geomagnetic storms and auroras were registered from September 9 onwards.

Then, on September 22, an X1.4-class solar flare erupted out of sunspot 1302. The blast produced a significant CME, but was not Earth directed. Two days later, an X1.9-class solar flare followed by a M7 one were unleashed out of the same sunspot. Both explosions propelled a pair of closely spaced CMEs. A strong-to-severe geomagnetic storm was reported on September 26.

October 2011

On October 22, 2011, the Sun unleashed a M1 flare with MCE, this time, was heading towards Mars.

November 2011

On November 3, 2011, active region 1339, one of the largest sunspots in years -40,000 km wide and at least twice that in length-, unleashed an X1.9-class solar flare. The related CME was not headed for Earth.

December 2011

Solar activity increased again in late-December, with the Sun unleashing M-flares. The most intense flare, produced by sunspot 1385, was an M4-class flare at 18:16 UTC on December 25.

January 2012

Active sunspot 1401 erupted an M3-class solar flare and a full-halo CME on January 19, 2012. The CME hit Earth's magnetic field in early hours of January 22, with minor geomagnetic disturbances reported.
Sunspot 1402 erupted a long-duration M8.7-class flare, followed by a CME, on January 23, 2012 at 03:59 UTC. According to NOAA, the flare's radiation storm was ranked as an S3 (strong level), the strongest since May 2005. The very fast-moving CME arrived Earth on January 24 at approximately 15:00 UTC. Geomagnetic storm reached a G1 level (minor), the same level recorded by the previous M3-class flare.

The Solar Heliospheric Observatory captured the CME (video shows the sun's activity from January 19 to January 23, 2012).

SOHO view of M9 flare.

The SDO captured this flare.

The SDO captured this flare.

Footage of the flare imaged at two different wavelengths followed by the CME.

On January 27, at 18:37 UT, sunspot region 1402 unleashed a X1.7-class flare, prompting NOAA's Space Weather Prediction Center to issue an R3 (strong) Radio Blackout warning and an S2 (moderate) Solar Radiation Storm warning. Sunspot 1402 was rotating onto the far side of the sun, so the blast site was not facing Earth. The explosion also produced a huge CME, but not Earth-oriented, so no geomagnetic storm was expected .

See also

• Earth's magnetic field
• List of solar cycles
• March 1989 geomagnetic storm
• Solar storm of 1859
• Solar variation

External links

• Solar Cycle Progression at NASA
• Solar Cycle Progression at the National Oceanic and Atmospheric Administration

• Solar Cycle 24 at the National Oceanic and Atmospheric Administration