September 23, 2000 SEARCH

Sunspot Group 9169

Massive Sunspot Appears

By Larry O'Hanlon, Discovery.com News

Sept. 22, 2000 -- The biggest sunspot in nine years has reared its menacing head and could wallop Earth with powerful solar storms within the next few days.

Sunspot Group 9169 covers about 6 billion square kilometers (2 billion square miles) and is 12 times larger than the entire surface of the Earth. It is rotating into position dead center on the sun today and tomorrow, say space weather forecasters at the Space Environment Center in Boulder Colorado. That means that if it blows its top, the radiation and interstellar shock wave will be aimed right at us.

"That is one of the largest of the cycle," says forecaster Larry Combs, referring to the approximately 11-year solar cycle of sunspot activity. "It's definitely a very complex region."

The sunspot group rotated around the edge of the sun and into view a few days ago, and has behaved itself for the most part, Combs says. Before it came into view there were signs of some outbursts called coronal mass ejections (CMEs) just over the edge of the sun's horizon that might have been caused by Group 9169, but they can't be sure.

"It was full grown when it came into view," Combs says. That means that unlike a sunspot last week that appeared explosively out of nowhere and launched a series of flares and CMEs, the mammoth Group 9169 group is behaving itself -- so far.

It could be worse: in 1947 there was a sunspot three times larger than Group 9169. That's 36 times the entire area of Earth's surface, or 18 billion square kilometers (7 billion square miles). It outsized all the others of the 20th century, say NASA scientists.

The good news about Group 9169 is that it's making up for the odd scarcity of sunspots the sun has had over the past couple of weeks.

"We're getting some better sunspot numbers," confirms solar scientist Jo Ann Joselyn of the University of Colorado in Boulder. "This is just typical maximum conditions."

Solar scientists estimate that we are currently at peak of the 11-year sunspot cycle, which is a calculated average of numbers of sunspots which researchers figure out months after the solar maximum has actually passed. Until Group 9169 popped into view, however, things were beginning to look suddenly a lot like the solar minimum, says Combs.

http://www.discovery.com/news/briefs/20000922/sp_sunspot.html

-- Martin Thompson (mthom1927@aol.com), September 23, 2000

Answers

Friday, 22 September, 2000, 01:03 GMT 02:03 UK Giant sunspot comes into view

By BBC News Online science editor Dr David Whitehouse The largest spot seen on the Sun for nine years has moved into view.

The spot, which is moving towards the centre of the Sun's disk, covers an area a dozen times larger than the entire surface of the Earth.

It comes at a time when the Sun is going through the maximum phase of its 11-year cycle of activity.

Astronomers are analysing the structure of the sunspot Picture: Franky Dubois Astronomers say that intense magnetic fields growing above the sunspot are being twisted into an unstable configuration that may produce a powerful burst of energy or flare.

Sunspots are believed to be caused when magnetic fields, shaped into huge coils, emerge on to the solar surface from below.

Surface gas is cooled slightly and appears darker than the surrounding hot gas. If a sunspot was on its own, it would be incredibly bright.

Although the latest sunspot - in solar active region 9169 - is exceptionally large, it is not a record-breaker, according to Dr David Hathaway, of Nasa's Marshall Space Flight Center in the US.

Power lines knocked out

The largest known sunspot was seen in 1947, and was three times larger than this latest feature.

A large sunspot in March 1989 triggered a disturbance in the Earth's magnetic field that knocked out power lines in Canada.

The spot is moving towards the centre of the Sun's disk Picture: Big Bear Solar Observatory Astronomers measure the sizes of sunspots as fractions of the Sun's visible area. The current sunspot is 2,140 millionths of this area.

By comparison, the entire surface area of the Earth is only 169 millionths of the Sun's visible hemisphere.

One of the best close-up images of the sunspot was obtained by amateur astronomer Franky Dubois from his private observatory in Belgium.

Mr Dubois told BBC News Online that it was one of the most spectacular sunspots he had ever seen.

Solar telescopes around the world have already focused on the sunspot to analyse its detailed structure and how it will change over time.

Astronomers are keen to point out that to observe sunspots care is needed.

They say no-one should ever look directly at the Sun under any circumstances, with or without optical aids, as this can cause blindness.

http://news.bbc.co.uk/hi/english/sci/tech/newsid_936000/936606.stm

-- Martin Thompson (mthom1927@aol.com), September 23, 2000.

The susnspot described above, plus another much smaller one, were both visible a few days ago to the "naked eye" (which really means visible without magnification, BUT with appropriate safety equipment). As the sun rotates, they will slowly move out of sight. I haven't been able to check on them since Friday due to weather here in the northeast.

It is rare but not unheard-of for sunspots to be visible without magnification; indeed, the ancient Chinese knew of sunspots because they saw them when the sun was in fog just thick enough to make viewing possible. In some 10 years as an avid amateur astronomer, this is the first time I have personally seen *two* "naked eye" sunspots at the same time.

The easiest way to view these sunspots is with small cardboard/ mylar "eclipse viewing" glasses--I have had mine for so long I don't know where to suggest you look. Be warned: the mylar (aluminum-coated plastic) used in the glasses is not necessarily the same as in cheap mylar balloons, do not substitute! If you don't have access to certified mylar eclipse glasses, welding glass is OK too (but there is a specific darkness number that is suitable, check astronomy resources on-line to get the right number).

Various resources on the web, www.spaceweather.com and so on, have lots of further details. Of note to this board, the sunspot called 9169 is magnetically extremely complex, and this level of complexity has in the past been associated with massive flares. It remains unclear whether 9169 will erupt, and if so, whether any of the solar activity will be pointed so as to hit Earth. Of course, such activity can be associated with disruption (induced voltages) in electric grid systems, and caused a massive blackout in eastern Canada in 1989.

-- Andre Weltman (aweltman@state.pa.us), September 25, 2000.

Thanks Andre.

There were 3 M-class flares yesterday. WEEKEND SOLAR FLARES:
A series of three M-class x-ray
solar flares erupted during a 24-hour
period beginning at 0330 UT
on Sept. 24th (11:30 pm EDT on Sept 23rd).
At least one of the
explosions came from active region 9166
near the west limb of
the Sun. SOHO images of these events are
not yet available, but
stay tuned for further details.

Space Weather

-- spider (spider0@usa.net), September 25, 2000.