Storms and Declining Solar Activity

Figure 2-12, corresponding to solar cycle 19, suggests that ionospheric storms have a peak following the maximum in sunspot number. This is evidently a general statement. Still, to this day, the popular view within the public at-large, as well as some otherwise well-informed telecommunication specialists, is that the sunspot maximum period is all important. The myth that the peak of the smoothed sunspot cycle is the only thing that matters was surely broken in the latter half of 2003, a period of decline in sunspot levels. From Figure 2-9 it is seen that there are two minor peaks in the number of sunspots in July and October-November of 2003 but the 12-month running mean is ~ 60 during the period. The period between mid-October and mid-November of 2003 produced some of the most intense flares and stormy periods seen during the entire solar cycle. Figure 2-13 shows the flare production from active region 486 between 10-24-04 and 1104-04.

Figure 2-14 is a redrawn version of a white light image of the sun on 28 October 2003. The sunspot regions shown 484, 486, 487, 488, and 492 with region 486 being the most important. It was the largest sunspot region observed since 1990, and it retained its size and complex magnetic structure for the full transit across the visible solar surface. There were 17 major flares from October 19th to November 5th, 2003; and 12 originated from region 486.

The magnetic storm phenomenon is probably the most important ramification of sunspot activity. We will now take an abbreviated look at the magnetosphere and geomagnetic storm activity.

Figure 2-12: Comparison of sunspot number, the number of ionosphere, and the number of SIDs during solar cycle 19 (1954-1964], After Jacobs and Cohen [1979],

Sunspot 486

10/24 10/25 10/25 10/27 10/28 10/29 10/30 10/31 11/01 11/02 11/03 11/04

Sunspot 486

10/24 10/25 10/25 10/27 10/28 10/29 10/30 10/31 11/01 11/02 11/03 11/04

X+ Class

1

X Class

M Class ■ ■■ -,

m —

.

1 . 1

1

Figure 2-13: Progression of Active Region 486 during the period from 10-24-04 and 11-04-04. The figure is from Simpson [2003]. The image is due to the NASA-SOHO program, the flare data is derived from NOAA, and the compilation is by Metatech Corporation.

Below we have provided a combined excerpt of NOAA-SEC Advisory Outlook #03-44 and Space Weather Advisory Bulletin #03-5.

Summary for October 27-November 4, 2003:

Space weather during the past week reached extreme levels. The dynamic solar region, NOAA Active region 486, continues to produce high levels of solar activity. Region 486 produced a category R4 (severe) radio blackout on October 28 at 11:10 UTC. Associated with this flare was a category S4 (severe) solar radiation storm beginning at 0025 UTC on 29 October. A coronal mass ejection (CME) was also associated, and it produced a G5 (extreme) geomagnetic storm starting at 0613 UTC on 29 October. This persisted at the G3-G5 levels for 24 hours. Region 486 continued to produce solar activity with yet another major flare at 2049 UTC on 29 October, resulting in an R4 (severe) radio blackout. A CME was also associated with this flare. Moving at 5 million miles per hour, the CME impacted the earth's magnetic field at 1620 UTC on October 30'h, and produced a category G5 (extreme) magnetic storm. Stormy conditions persisted for 24 hours. Region 486 grew to become the largest sunspot region of cycle 23.

Giant sunspot region 486 unleashed another intense solar flare on November 4th at 1950 UTC. The blast saturated sensors onboard GOES satellites. The last time that happened, in April 2001 (i.e., near the peak of the cycle), the flare that saturated the sensors was classified as an X20, the biggest ever recorded at that time. The November 4th flare appears to have been stronger. Because sunspot region 486 was near the sun's western limb, the blast was not directed toward earth.

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