太陽黑子周期揭密神奇蝴蝶圖英語美文
Sunspot Cycles: Deciphering the Butterfly Pattern
150多年以前，科學(xué)家證實(shí)，太陽黑子的活動(dòng)是周期性的，它的平均周期約為11年;大約90年以前，科學(xué)家在這一研究領(lǐng)域又有了新的突破，他們繪制出太陽黑子周期性變化示意圖后，發(fā)現(xiàn)赫然呈現(xiàn)在紙上的竟是一只只翩翩起舞的“蝴蝶”;而現(xiàn)在科學(xué)家又有了新的任務(wù)，他們正試圖揭開這幅太陽黑子“蝴蝶圖”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.
國際在線消息：150多年以前，科學(xué)家證實(shí)，太陽黑子的活動(dòng)是周期性的，它的平均周期約為11年;大約90年以前，科學(xué)家在這一研究領(lǐng)域又有了新的突破，他們繪制出太陽黑子周期性變化示意圖后，發(fā)現(xiàn)赫然呈現(xiàn)在紙上的竟是一只只翩翩起舞的“蝴蝶”;而現(xiàn)在科學(xué)家又有了新的任務(wù)，他們正試圖揭開這幅太陽黑子“蝴蝶圖”的秘密……
據(jù)美國“每日科學(xué)”網(wǎng)站2月4日?qǐng)?bào)道，有關(guān)研究者表示，揭開“蝴蝶圖”的秘密可以讓科學(xué)工作者更好地預(yù)測太陽風(fēng)暴(solar storms)何時(shí)來臨。太陽風(fēng)暴爆發(fā)時(shí)，將會(huì)影響通訊、威脅衛(wèi)星、破壞臭氧層，這與人們的生活息息相關(guān)，所以這項(xiàng)研究具有十分重要的意義。
太陽黑子和太陽黑子周期
想揭開問題的謎底，我們必須要對(duì)下面一些基本概念有所了解。首先我們要知道什么是太陽黑子(sunspots)和太陽黑子周期(sunspot cycle)。
太陽黑子是人們最早發(fā)現(xiàn)也是人們最熟悉的一種太陽表面活動(dòng)。明亮的太陽光球表面經(jīng)常出現(xiàn)一些小黑點(diǎn)，這就是太陽黑子。美國國家大氣研究中心高地天文臺(tái)的太陽天文學(xué)家埃米·諾頓解釋說，太陽黑子之所以產(chǎn)生是因?yàn)樘杻?nèi)部磁場發(fā)生變化的結(jié)果。
太陽黑子的數(shù)量并不是固定的，它會(huì)隨著時(shí)間的變化而上下波動(dòng)，每11年會(huì)達(dá)到一個(gè)最高點(diǎn)，這11年的時(shí)間就被稱之為一個(gè)太陽黑子周期。太陽黑子周期是1843年由一名德國天文學(xué)家發(fā)現(xiàn)的。
諾頓表示，不僅是太陽黑子的數(shù)量會(huì)在這11年中發(fā)生變化，同時(shí)它們所處的位置也會(huì)隨之改變。每當(dāng)一個(gè)太陽黑子周期開始的時(shí)候，最先出現(xiàn)的黑子總是在離赤道較遠(yuǎn)處(平均緯度為35度)，然后由高緯度向低緯度方向移動(dòng)，最終黑子出現(xiàn)的位置漸漸靠近太陽赤道。
翩翩起舞的“蝴蝶圖”
1904年，英國天文學(xué)家愛德華·蒙德發(fā)現(xiàn)了一幅奇異的景象，記錄太陽黑子周期變化的圖表竟然呈現(xiàn)出一幅展翅欲飛的蝴蝶圖案。
蒙德以緯度為縱坐標(biāo)，以時(shí)間(年份)為橫坐標(biāo)，繪出太陽黑子的分布圖后，發(fā)現(xiàn)漸漸靠近赤道的太陽黑子就像蝴蝶的兩只翅膀。如果把幾個(gè)太陽黑子周期的圖案繪制在一起，就組成了一連串翩翩起舞的“蝴蝶”。
神秘的太陽發(fā)電機(jī)效應(yīng)
目前，科學(xué)家們正致力于研究這個(gè)神奇的太陽黑子“蝴蝶圖”。太陽天文學(xué)家諾頓說，要想揭開謎底，首先要從所謂的太陽發(fā)電機(jī)效應(yīng)(Solar Dynamo)說起。她說：“太陽發(fā)電機(jī)效應(yīng)是太陽物理學(xué)中最為神秘的事物之一，它指的是在太陽內(nèi)部和太陽表面的機(jī)械運(yùn)動(dòng)轉(zhuǎn)化成磁能的過程�！�
因?yàn)樘柡谧踊顒?dòng)區(qū)域被認(rèn)為是強(qiáng)磁場區(qū)，同時(shí)太陽黑子會(huì)在11年的周期內(nèi)發(fā)生增多和減少的現(xiàn)象，所以科學(xué)家認(rèn)為太陽磁場也會(huì)在這一時(shí)期內(nèi)增強(qiáng)或減弱。諾頓說：“太陽黑子周期的循環(huán)性是證明太陽內(nèi)部磁場在這個(gè)周期里發(fā)生變化有力的證據(jù)。”
諾頓和她的同事建立了太陽表面和內(nèi)部的不同種類的熱氣流電腦模型，他們認(rèn)為這有助于更好地了解太陽發(fā)電機(jī)效應(yīng)，同時(shí)也有助于解釋太陽黑子移動(dòng)產(chǎn)生“蝴蝶圖”的原因。
最佳理論
諾頓的同事吉爾曼說，對(duì)于太陽黑子活動(dòng)圖為什么會(huì)呈現(xiàn)蝴蝶圖案這個(gè)問題，目前還沒有一個(gè)統(tǒng)一的科學(xué)結(jié)論。其中，最主要的理論是以吉爾曼同事迪科派蒂的電腦模擬為基礎(chǔ)的。
迪科派蒂的電腦模擬將太陽黑子的移動(dòng)和被稱為經(jīng)向流的`等離子流聯(lián)系了起來。經(jīng)向流在太陽赤道和兩極之間流動(dòng)，它的全部過程被稱之為太陽活動(dòng)周期。
經(jīng)向流就像擁有兩個(gè)傳送帶的系統(tǒng)。這兩條“傳送帶”一個(gè)位于北半球，一個(gè)位于南半球，每個(gè)“傳送帶”都沿著太陽表面，從赤道運(yùn)動(dòng)到北極或是南極。到達(dá)極地時(shí)，每條“傳送帶”會(huì)轉(zhuǎn)個(gè)彎，進(jìn)入太陽內(nèi)部。經(jīng)向流經(jīng)過太陽內(nèi)部的最外層即環(huán)流區(qū)返回到赤道。當(dāng)“傳送帶”到達(dá)太陽赤道時(shí)，它又會(huì)轉(zhuǎn)頭沿著來的路徑，重新回到太陽表面，開始新一輪的循環(huán)。
一個(gè)太陽活動(dòng)周期的時(shí)間為22年，或者說是兩個(gè)太陽黑子周期。這個(gè)理論認(rèn)為，“傳送帶”的兩半都擁有相似的太陽黑子圖案，這就是為什么太陽黑子活動(dòng)遵循著11年的周期——等于太陽活動(dòng)周期的一半。
根據(jù)迪科派蒂的的理論，太陽黑子在太陽表面流動(dòng)會(huì)留下痕跡，這種痕跡還被帶到太陽內(nèi)部，科學(xué)家們相信，太陽黑子的磁場在這里形成，而新的太陽黑子則是在最近周期內(nèi)的痕跡上形成的。
通過了解經(jīng)向流速度的變化以及過去的太陽黑子周期，迪科派蒂和同事相信他們也許能夠預(yù)測太陽黑子活動(dòng)的時(shí)間和強(qiáng)度，從而也能對(duì)太陽風(fēng)暴有所了解。他說：“事實(shí)上，在最近的工作中，我們預(yù)測因?yàn)榻?jīng)向流在目前周期內(nèi)的速度放慢，所以下一個(gè)周期，即周期24的開始將會(huì)被推遲。”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.
【太陽黑子周期揭密神奇蝴蝶圖英語美文】相關(guān)文章：
人生的蝴蝶效應(yīng)英語美文閱讀08-01
愛的周期性愛情美文08-29
蝴蝶夢經(jīng)典美文05-26
蝴蝶結(jié)的折紙步驟圖02-04
手工折紙蝴蝶的步驟圖超詳細(xì)11-20
血梅圖美文摘抄09-18
蝴蝶不悲傷美文摘抄08-16
神奇的英語短語08-13
英語經(jīng)典美文01-27