第24届太阳活动周期开始了 ！
Jan. 10, 2008: Hang on to your cell phone, a new solar cycle has just begun."On January 4, 2008, a reversed-polarity sunspot appeared—and this signals the start of Solar Cycle 24," says David Hathaway of the Marshall Space Flight Center.
Solar activity waxes and wanes in 11-year cycles. Lately, we've been experiencing the low ebb, "very few flares, sunspots, or activity of any kind," says Hathaway. "Solar minimum is upon us."
The previous solar cycle, Solar Cycle 23, peaked in 2000-2002 with many furious solar storms. That cycle decayed as usual to the present quiet leaving solar physicists little to do other than wonder, when would the next cycle begin?
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"New solar cycles always begin with a high-latitude, reversed polarity sunspot," explains Hathaway. "Reversed polarity" means a sunspot with opposite magnetic polarity compared to sunspots from the previous solar cycle. "High-latitude" refers to the sun's grid of latitude and longitude. Old cycle spots congregate near the sun's equator. New cycle spots appear higher, around 25 or 30 degrees latitude.
The sunspot that appeared on January 4th fits both these criteria. It was high latitude (30 degrees N) and magnetically reversed. NOAA named the spot AR10981, or "sunspot 981" for short.
Sunspot 981 was small--only about as wide as Earth, which counts as small on the grand scale of the sun--and it has already faded away. But its three day appearance on Jan. 4-6 was enough to convince most solar physicists that Solar Cycle 24 is underway.
太阳黑子的活动与地球气候关系密切。下面的树桩是北京香山公园附近砍伐的，从树轮看有20多年的树龄，可以清晰看到23－22太阳活动周期的痕迹。
[ 本帖最后由 雪山飞鱼 于 2008-3-10 09:59 编辑 ] 好设备，年轮上怎么看痕迹呢？我没看出来，楼主给比喻说明下？::070821_02.jpg:: 树木的年轮是生长的痕迹，水量充沛长势良好的年份，树轮就宽，遇到干旱或其他灾害气象长势不好的时候，年轮窄，看起来就是年轮密集的位置，在这个树桩上明显看到了三个年轮密集的位置，他们的间隔约11年左右。
最外层的树轮是砍伐时的年代，一直数到树心，年轮的个数是这个大树的年龄。
科学家们据对我国两千多年太阳黑子活动的记录分析，在太阳黑子极大年附近，我国易发生严重干旱、暑热灾害。
这是太阳活动周期对地球气候影响的证据之一。
[ 本帖最后由 雪山飞鱼 于 2008-3-10 09:45 编辑 ]
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感兴趣的朋友们在户外活动或爬山的时候，请注意观察这样的树墩，拍照，记下发现地点，这是个非常有意义的科学探索活动。我国的气象科学家已经在新疆地区建立了很大的年轮库，记录了新疆地区5000多年的气候历史，在数码时代的今天，我们每个人都有机会参与到这样的科学实践中来。
寻找不同年代树木的年轮，可以是树桩，旧房屋的原木，或埋藏的老木头，通过特征明显的年轮把他们拼接到一起，就可以形成长长的时间尺，甚至在网上就可以建立与世界任何树轮库都可媲美的网上树轮数据库。
[ 本帖最后由 雪山飞鱼 于 2008-3-10 09:57 编辑 ]
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