人的记忆力会随着岁月的流逝而衰退，写作可以弥补记忆的不足，将曾经的人生经历和感悟记录下来，也便于保存一份美好的回忆。那么我们该如何写一篇较为完美的范文呢？下面是小编为大家收集的优秀范文，供大家参考借鉴，希望可以帮助到有需要的朋友。
太阳黑子周期变化规律 太阳黑子周期表篇一
sunspot cycles: deciphering the butterfly pattern
150多年以前，科学家证实，太阳黑子的活动是周期性的，它的平均周期约为11年;大约90年以前，科学家在这一研究领域又有了新的突破，他们绘制出太阳黑子周期性变化示意图后，发现赫然呈现在纸上的竟是一只只翩翩起舞的“蝴蝶”;而现在科学家又有了新的任务，他们正试图揭开这幅太阳黑子“蝴蝶图”的秘密……
a little more than 150 years ago, scientists learned that the number of sunspots (temporarily cool, dark areas) on our sun waxes and wanes over a period of about 11 years. about 90 years ago, scientists learned that there"s a butterfly-shaped pattern to this cycle. now they are trying to learn what drives that pattern.
国际在线消息：150多年以前，科学家证实，太阳黑子的活动是周期性的，它的平均周期约为11年;大约90年以前，科学家在这一研究领域又有了新的突破，他们绘制出太阳黑子周期性变化示意图后，发现赫然呈现在纸上的竟是一只只翩翩起舞的“蝴蝶”;而现在科学家又有了新的任务，他们正试图揭开这幅太阳黑子“蝴蝶图”的秘密……
据美国“每日科学”网站2月4日报道，有关研究者表示，揭开“蝴蝶图”的秘密可以让科学工作者更好地预测太阳风暴(solar storms)何时来临。太阳风暴爆发时，将会影响通讯、威胁卫星、破坏臭氧层，这与人们的生活息息相关，所以这项研究具有十分重要的意义。
太阳黑子和太阳黑子周期
想揭开问题的谜底，我们必须要对下面一些基本概念有所了解。首先我们要知道什么是太阳黑子(sunspots)和太阳黑子周期(sunspot cycle)。
太阳黑子是人们最早发现也是人们最熟悉的一种太阳表面活动。明亮的太阳光球表面经常出现一些小黑点，这就是太阳黑子。美国国家大气研究中心高地天文台的太阳天文学家埃米·诺顿解释说，太阳黑子之所以产生是因为太阳内部磁场发生变化的结果。
太阳黑子的数量并不是固定的，它会随着时间的变化而上下波动，每11年会达到一个最高点，这11年的时间就被称之为一个太阳黑子周期。太阳黑子周期是1843年由一名德国天文学家发现的。
诺顿表示，不仅是太阳黑子的数量会在这11年中发生变化，同时它们所处的位置也会随之改变。每当一个太阳黑子周期开始的时候，最先出现的黑子总是在离赤道较远处(平均纬度为35度)，然后由高纬度向低纬度方向移动，最终黑子出现的位置渐渐靠近太阳赤道。
翩翩起舞的“蝴蝶图”
1904年，英国天文学家爱德华·蒙德发现了一幅奇异的景象，记录太阳黑子周期变化的图表竟然呈现出一幅展翅欲飞的蝴蝶图案。
蒙德以纬度为纵坐标，以时间(年份)为横坐标，绘出太阳黑子的分布图后，发现渐渐靠近赤道的太阳黑子就像蝴蝶的两只翅膀。如果把几个太阳黑子周期的图案绘制在一起，就组成了一连串翩翩起舞的“蝴蝶”。
神秘的太阳发电机效应
目前，科学家们正致力于研究这个神奇的太阳黑子“蝴蝶图”。太阳天文学家诺顿说，要想揭开谜底，首先要从所谓的太阳发电机效应(solar dynamo)说起。她说：“太阳发电机效应是太阳物理学中最为神秘的事物之一，它指的是在太阳内部和太阳表面的机械运动转化成磁能的过程。”
因为太阳黑子活动区域被认为是强磁场区，同时太阳黑子会在11年的周期内发生增多和减少的现象，所以科学家认为太阳磁场也会在这一时期内增强或减弱。诺顿说：“太阳黑子周期的循环性是证明太阳内部磁场在这个周期里发生变化有力的证据。”
诺顿和她的同事建立了太阳表面和内部的不同种类的热气流电脑模型，他们认为这有助于更好地了解太阳发电机效应，同时也有助于解释太阳黑子移动产生“蝴蝶图”的原因。
最佳理论
诺顿的同事吉尔曼说，对于太阳黑子活动图为什么会呈现蝴蝶图案这个问题，目前还没有一个统一的科学结论。其中，最主要的理论是以吉尔曼同事迪科派蒂的电脑模拟为基础的。
迪科派蒂的电脑模拟将太阳黑子的移动和被称为经向流的`等离子流联系了起来。经向流在太阳赤道和两极之间流动，它的全部过程被称之为太阳活动周期。
经向流就像拥有两个传送带的系统。这两条“传送带”一个位于北半球，一个位于南半球，每个“传送带”都沿着太阳表面，从赤道运动到北极或是南极。到达极地时，每条“传送带”会转个弯，进入太阳内部。经向流经过太阳内部的最外层即环流区返回到赤道。当“传送带”到达太阳赤道时，它又会转头沿着来的路径，重新回到太阳表面，开始新一轮的循环。
一个太阳活动周期的时间为22年，或者说是两个太阳黑子周期。这个理论认为，“传送带”的两半都拥有相似的太阳黑子图案，这就是为什么太阳黑子活动遵循着11年的周期——等于太阳活动周期的一半。
根据迪科派蒂的的理论，太阳黑子在太阳表面流动会留下痕迹，这种痕迹还被带到太阳内部，科学家们相信，太阳黑子的磁场在这里形成，而新的太阳黑子则是在最近周期内的痕迹上形成的。
通过了解经向流速度的变化以及过去的太阳黑子周期，迪科派蒂和同事相信他们也许能够预测太阳黑子活动的时间和强度，从而也能对太阳风暴有所了解。他说：“事实上，在最近的工作中，我们预测因为经向流在目前周期内的速度放慢，所以下一个周期，即周期24的开始将会被推迟。”a little more than 150 years ago, scientists learned that the number of sunspots (temporarily cool, dark areas) on our sun waxes and wanes over a period of about 11 years. about 90 years ago, scientists learned that there"s a butterfly-shaped pattern to this cycle. now they are trying to learn what drives that pattern.
understanding what generates the sunspot pattern may allow scientists to provide better forecasts of solar storms, which can cause power outages and disrupt satellite communications on earth.
but first, what are sunspots? what"s the sunspot cycle? and what"s this pattern?
sunspots are thought to result from a shifting magnetic field inside the sun, explains aimee norton, a solar astronomer with the high altitude observatory at the national center for atmospheric research in boulder, colorado.
the number of sunspots fluctuates over time, reaching a peak every 11 years. this 11-year pattern is known as the sunspot cycle and was discovered in 1843 by german astronomer samuel heinrich.
not only does the number of sunspots fluctuate over the 11-year period, but so too do their locations, norton said. over the period, the sunspots migrate from about 35 degrees north and south latitude toward the sun"s equator.
in 1904 english astronomer edward maunder noticed an artful pattern to the cycle.
when the latitude and time of sunspots from an entire cycle are plotted on a map, the migration of sunspots toward the equator looks like two wings of a butterfly. several cycles plotted together look like a trail of butterflies.
solar dynamo
scientists are now trying to understand why the sunspot belt moves toward the equator over the course of the 11-year cycle. to understand this, norton said, requires understanding the so-called solar dynamo.
"this is one of the major mysteries in solar physics," she said. "the dynamo is a process by which the mechanical motions on and in the sun are converted into magnetic energy."
since sunspots are believed to be regions of intense magnetic field and since they increase and decrease over an 11-year cycle, scientists believe that the sun"s magnetic field must also increase and decrease in time.
"the cyclical nature of the sunspot cycle is strong evidence that the magnetic field within the sun is being regenerated during this cycle," norton said.
generated by the flow of hot gases, the sun"s electric currents in turn generate magnetic fields.
norton and her colleagues are building computer models of the various flows on and in the sun to help them understand the solar dynamo. this should, in turn, explain the reason for the sunspot migration pattern.
"some details of the migration pattern as observed in spot behavior is beyond the current capability of dynamo models to produce, but it may be possible with more elaborate models now under development," said peter gilman, a colleague of norton"s at the high altitude observatory.
best theory
gilman said there is no scientific consensus on why sunspot-migration diagrams take the shapes of butterflies. a leading theory is based on computer modeling by colleague gilman"s colleague mausumi dikpati.
dikpati"s models link the migration to a current of plasma called the meridional flow, which circulates between the sun"s equator and its poles. it"s all part of a process called the hale cycle.
the flow is like a system of two conveyor belts, one in the northern hemisphere and one in the southern hemisphere. each belt travels along the surface of the sun, from the equator to the pole (north or south, depending on the hemisphere). at its pole, each belt turns the corner, diving into the sun"s interior.
the flow makes its return trip to the equator through the convection zone, the outermost layer of the sun"s interior. as the belt approaches the equator, it turns and follows a path toward the sun"s surface, and the cycle begins again.
a single hale cycle takes about 22 years, or two sunspot cycles. the thinking is that the two halves of the "conveyor belt" have similar sunspot patterns on them, which is why sunspot activity follows an 11-year cycle—half a hale cycle.
according to dikpati"s theory, sunspots leave an imprint on the surface flow. this imprint is carried into the interior, where scientists believe the sunspot-producing magnetic fields are generated. new sunspots form based on the imprints created during the most recent cycle.
by understanding the variation of the meridional flow"s speed and the sun"s past sunspot cycles, dikpati and colleagues believe they may be able to forecast the timing and intensity of sunspot activity—and therefore of solar storms.
"in fact, in a very recent work, we are predicting the onset of the next cycle—cycle 24—will be late, because the meridional flow slowed down in the current cycle," dikpati said.
according to the forecast, the next solar cycle will begin in 2007 to 2008. that means that cycle 24 would begin about a half year late, or about 11 years and six months after the beginning of cycle 23.
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