On Nov. 4th, 2003, the Sun produced the largest explosion ever recorded in our solar system. The flare originated from solar active region 10486, however, unlike the preceding powerful flares produced from this region, this explosion was not directed toward the Earth, and so its effects were relatively minimal.
Solar active region 10486, which had grown to one of the largest sunspots seen by the Solar and Heliospheric Observatory (SOHO), unleashed a spectacular show last week producing a series of powerful flares and associated plasma eruptions into space called Coronal Mass Ejections (CME). Flares are intense solar magnetic explosions (the biggest bang in our solar system). One of the recent flares was the second largest observed by SOHO and the third largest ever recorded. It launched a stream of high energy protons toward the Earth at close to the speed of light, taking approximately fifteen minutes to reach Earth and be recorded by the Division's neutron monitors installed at Mawson and Kingston. The flare can be seen as a bright flash in SOHO ultraviolet images (upper right). It was associated with a CME (lower left), which sent a large plasma cloud directly towards Earth. The expanding CME cloud and the effect of the high energy protons on the SOHO imager (multiple white spots) can be seen in the lower right image. The fast-moving cloud first impacted Earth's magnetosphere a mere 19 hours later, almost a record speed (>2000 km/s) for a CME.
As a result of this solar storm, an impressive sudden magnetic impulse was detected on all our station magnetometers that also recorded the subsequent intense geomagnetic storms. High energy protons caused a series of Polar Cap Absorption (PCA) events as detected on our station riometers. These space weather events were reported to impact upon space and ground based technologies: two spacecraft were significantly damaged by the high energy particle bombardment; a disturbed ionosphere impacted on HF communications; and some 20,000 homes lost power in Malmoe, in southern Sweden as a consequence of induced currents tripping circuit breakers in the power grid.
The auroral oval expanded considerably and moved away from our Antarctic stations, over Macquarie Island and Tasmania (as observed by the TIGER radar on Bruny Island) and then equatorward - aurora were seen as far north as Perth and Wollongong. But unfortunately persistent cloud cover over Hobart and Kingston meant that only the occasional glimpse of aurora could be seen through gaps in the cloud. And only then by the keen auroral observer - like John I. who reported his observations to IPS Radio and Space Services:
"The aurorae we have seen through the gaps looked quite active at times. The best I've seen (most colourful and active) was a short (10 min) glimpse we had on Friday night (31st Oct), about 10:30 pm local summer time. (It may have been closer to 10:45 pm.) To the south a large window in the clouds opened, and we had a bright white-green glow topped with red, but otherwise unstructured, and a series of fast growing, narrow, and short lived rays. The glow extended to perhaps 30 degrees about the south horizon, with the tops of the rays extending to around 60 degrees. The lower border of the glow was not determinable due to cloud. The rays grew and decayed in around 10 seconds, at times less, and were less than approximately 1 degree in apparent width."
Flares and CMEs are still being generated by the solar active region 10486. IPS Radio and Space Services issue event warnings on their web site and welcome confirmation of sightings of aurorae. SAS station experimental data are used for IPS space weather forecasts.
- Information about auroras