Solar cycle 23
Solar cycle 23 was the 23rd solar cycle since 1755, when recording of solar sunspot activity began.[1][2] The solar cycle lasted 12.6 years, beginning in May 1996 and ending in January 2008. The maximum smoothed sunspot number (monthly number of sunspots averaged over a twelve-month period) observed during the solar cycle was 120.8, and the minimum was 1.7.[3] There were a total of 805 days with no sunspots during this cycle.[4][5][6]
One of the first major aurora displays of solar cycle 23 occurred on 6 April 2000, with bright red auroras visible as far south as Florida and South Europe.[7] On 14 July 2000, the Coronal Mass Ejection (CME) hurled by a X5.7 solar flare provoked an extreme (G5 level) geomagnetic storm the next day. Known as the Bastille day event, this storm caused damage to GPS systems and in some power companies.[citation needed] Auroras were visible as far south as Texas.[8] Another major aurora display was observed on 1 April 2001, due to a CME hitting the Earth's magnetosphere. Auroras were observed as far south as Mexico and South Europe. The following day, a very large solar flare occurred on 2 April 2001, an X20-class, but the blast was directed away from Earth. This flare was the second most powerful ever recorded.
In late October 2003, a series of large solar flares occurred. A X17.2-class flare ejected on 28 October 2003 resulted in auroras visible as far south as Florida and Texas. A G5 level geomagnetic storm blasted the Earth's magnetosphere the next two days. [9] A few days later, the largest solar flare ever measured with instruments occurred on 4 November 2003; initially measured at X28, it was later upgraded to an X45-class.[10][11] This flare was not Earth-oriented and thus only resulted in high-latitude auroras. The whole sequence of events occurred from 28 October to 4 November is known as the Halloween Storm. Other very large solar flares occurred on 7 September 2005 (X17), 15 April 2001 (X14.4) and 29 October 2003 (X10), with auroras visible in mid-latitudes.
A complete list of the larger solar flares of this cycle is available at spaceweather.com[12]
References
- ^ Kane, R.P. (2002). "Some Implications Using the Group Sunspot Number Reconstruction". Solar Physics 205(2), 383-401.
- ^ "The Sun: Did You Say the Sun Has Spots?". Space Today Online. Retrieved 12 August 2010.
- ^ "SIDC Monthly Smoothed Sunspot Number".
- ^ "Spotless Days".
- ^ "What's Wrong with the Sun? (Nothing) more information: Spotless Days".
- ^ "Solaemon's Spotless Days Page".
- ^ "Brushfires in the Sky". nasa.gov. 25 April 2000. Retrieved 18 November 2010.
- ^ "A Solar Radiation Storm". nasa.gov. 14 July 2000. Retrieved 18 November 2010.
- ^ "Hotshot". nasa.gov. Retrieved 18 November 2010.
- ^ "Hotshot". nasa.gov. Retrieved 18 November 2010.
- ^ "Biggest ever solar flare was even bigger than thought". spaceref.com. 15 March 2004. Retrieved 18 November 2010.
- ^ "The Most Powerful Solar Flares Ever Recorded". spaceweather.com. Retrieved 18 November 2010.
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