Space weather effects of October?November 2003

Abstract

The period between late October and early November of 2003 included a series of large solar events that resulted in some of the most extreme space weather of the current solar cycle. Space weather has been defined as the conditions on the sun and in the solar wind, magnetosphere, ionosphere, and thermosphere that can influence the performance and reliability of space-borne and ground-based technological systems. Adverse conditions in the space environment can cause disruption of satellite operations, communications, navigation, and electric power distribution grids, leading to a variety of socioeconomic losses (National Science Foundation 2000). The space weather events of October–November 2003 were initiated by three very large sunspot clusters that became visible on the Sun over a period of approximately 7 days beginning on 18 October, 2003. One of these clusters, region 486, became the largest sunspot group of the current solar cycle and the largest seen since 1991. This sudden increase in sunspots induced a series of solar flares and coronal mass ejections (CMEs), (Department of Commerce 2004). Solar flares are explosions on the surface of the Sun that produce a quick directed high-speed blast of charged particles and electromagnetic energy. One of the largest solar flares ever seen on the Sun occurred on 28 October. It was the third largest detected since regular monitoring began approximately 30 years ago and the largest since April 2001 (US Department of Commerce 2004). This activity was accompanied by a CME. CME’s are huge bubbles of plasma ejected from the Sun that speed into space. They disrupt the flow of the solar wind and produce disturbances that can strike the Earth with sometimes-catastrophic results (http://science.nasa.gov/ssl/pad/solar/ cmes.htm). This particular CME was one of the fastest on record in that it left the sun with a speed of 2,500 km/s, five times the average speed (Murtagh 2004). Figure 1 illustrates the observed active regions on 27 October together with the images of the solar flare and CME recorded on 28 October as observed by the SOHO spacecraft (http://sohowww.nascom.nasa.gov/). These events resulted in a severe geomagnetic storm in the Earth’s environment at 06:00 UT on 29 October. The disturbance levels on the Sun remained high for several days with a second powerful CME occurring at approximately 21:00 UT on 29 October. Figure 2 illustrates the planetary 3-h Kp indices for the period of 29 October 2003 to 1 November 2003. The Kp index is derived from 13 global magnetic observatories. It is a measure of the disturbance level of the geomagnetic field by auroral ionospheric currents. Kp values greater than 4 represent disturbed conditions. As the Kp values increase, the severity of the storm increases. Kp values of 9 represent the most extreme disturbed conditions and occur only a few times during the course of each 11-year solar cycle (http://www.sec.noaa.gov/NOAAscales). Note that Kp values of 9 were reached multiple times during 29–30 October in response to the CME activity.