七月牡丹

海纳百川,有容乃大; 壁立千仞,无欲则刚. The finest souls are those who gulped pain and avoided making others taste it. -nizariat
正文

关于北极光的简单科普

(2020-03-01 18:05:46) 下一个

近两年开始回答客人问题,开始关注北极光的信息。 常听客人说起他们做攻略,Kp值,什么极光大年小年之类, 我的反应是,“是吗? 没听说过诶。” 这几天看阿拉斯加大学的地球物理研究所的网站,发现别人说的那些都在上面。 

 

https://www.gi.alaska.edu/monitors/aurora-forecast 网站在这里,关于极光的问题几乎都有回答,有兴趣的朋友可以自己去研究。我捡几个重点编译一下。

How often can I see aurora? 看到极光的机会是多少

只要有晴朗的黑暗的夜空,就能看到极光。 阳光和云层是极光的最大障碍。 
Where is the best place to see aurora? 看到极光的最佳地点
正常情况下,这些地方都可以看到北极光: 阿拉斯加的Fairbanks; 加拿大的Dawson city, Yellowknife, 和Gillam; 格陵兰的南端; 冰岛,挪威,西伯利亚。 
如果您在这些地点附近, 如果天气预报晴天, 3/4号会有大爆发, 3/5 号小爆发。
What is the best time of day to see aurora? 一天中看极光的最佳时间
子夜前后的四个小时。极光活跃的时候也可能从晚7点到早7点(圣诞节前后黑夜时间长),在Fairbanks发生过。 
What is the best time of year to see aurora? 一年中看极光的最佳时间
保险的估计每年的8月21号到4月21号(我最后一次看到北极光在4月29号,极光爆发4月22号)。不过,秋季阴天下雨/雪的机会是春天的两倍。 我个人喜欢四月初看北极光,不太冷,也不累。 当然,每年8月底都有一场大爆发,天气情况难以预测。 
 
Why are some years better than others to view the aurora? 为什么有的年份看极光比别的年份要好 -- 极光也有大年小年。 据说每11年一个周期,上次爆发年是2014年,那么下次应该是2025年。 
个人的经验:2014年还没有开始做民宿,那年我家的两个极光爱好者(先生和女儿)还真的疯狂地追了一夜,拍出了前所未有的整个天空的紫色蓝色极光。后来我亲身经历的是2016年的爆发。极光活跃的年份,住4晚上的客人看到极光的几率是95%以上。不活跃的年份,没有统计数字,反正今年至少有过15%的客人没有看到极光。 今天看了网站的抛物线, 才发现2020年在谷底,是极光最不活跃的年份。 
 
Where should I view the aurora when I'm in Fairbanks, Alaska? 在阿拉斯加的费尔班克斯看北极光的地点 (以前写过,暂不赘述。)
得去忙了。先到这里。
下面是草稿的一部分,都是从同一个网站搬来的,有空的朋友可以看着玩玩。
https://www.gi.alaska.edu/monitors/aurora-forecast
 

SCIENCE OF THE AURORA

VIEWING THE AURORA

How often can I see aurora?
There is always some aurora at some place on earth. When the solar wind is calm, the aurora might only be occurring at very high latitudes and might be faint, but there is still aurora. In order for us to see the aurora, however, the sky must be dark and clear. Sunlight and clouds are the biggest obstacles to auroral observations.
Where is the best place to see aurora?
 
What is the best time of day to see aurora?
The best time to watch for aurora is the three or four hours around midnight, but aurora occurs throughout the night. Active auroral displays tend to be more diffuse and fragmented later in the night, which means that 9 p.m. to 3 a.m. is typically the time period with the highest probability of seeing spectacular auroral displays over interior Alaska in winter.  Since clear sky and darkness are both essential to see aurora, the best time is dictated by the weather and by the sunrise and sunset times. The moon is also very bright and can make it more difficult to view the aurora, so lunar cycles should be taken into account.
What is the best time of year to see aurora?

Clear skies are a requirement, so you should try to choose a location and a season that is blessed with the clearest skies. The continental locations in Russia, Alaska and western Canada under the auroral zone statistically have the clearest skies. Note that during the spring, the skies of Iceland and Scandinavia are usually clear.  So the dark of the moon in March is the best time of year to travel to the auroral zone since the yearly cycle of auroral activity also peaks around the equinox.

Sunlight prevents viewing the aurora during the summer at high latitudes. The skies at night are simply too bright as the sun climbs in the sky until the June 21 solstice and then descends. Here in Fairbanks, at about latitude 64.8, our aurora viewing “season” is August 21 to April 21. The odds are in your favor between those dates: if the weather is clear and you stay for at least three nights, it’s highly likely (though never certain!) that you will see the aurora. From April 22 to August 20 although the sun does set the sky never gets dark enough in Fairbanks to see the aurora even if it was a spectacular display.

 

Why are some years better than others to view the aurora?
The number of sunspots on the Sun's surface changes on a fairly regular cycle, which scientists refer to as the sun's 11-year cycle variation. Sunspot activity, and hence auroral activity, tends to peak every 11 years. This peak is called the solar maximum. The last solar maximum was in 2014; the next is expected around 2025. The chances of seeing the aurora at lower latitudes increase when the sunspot cycle is at a maximum, but chances at higher latitudes are not as dependent on the solar maximum because the auroral oval is normally present.
Where should I view the aurora when I'm in Fairbanks, Alaska?

SCIENCE OF THE AURORA

What is the aurora?
What is the auroral oval?

The two figures below show the locations with the most frequent occurrences of aurora borealis (left) and aurora australis (right) during the period of best viewing around the middle of the night.

This level of auroral activity, index Kp=2, will occur often enough that you will probably see the aurora if you travel to these regions when the nights are dark and stay for three days to a week, assuming that the skies are clear. If the auroral activity level is higher than 2, you will still observe the stronger motions and color changes, etc., that are seen farther equatorward.

What makes the colors of the aurora?
What is the altitude of the aurora?
What are the types of aurora?
Can you hear the aurora?

The best answer is “Maybe.”

It is easy to say that the aurora makes no audible sound. The upper atmosphere is too thin to carry sound waves, and the aurora is so far away that it would take a sound wave five minutes to travel from an overhead aurora to the ground. But many people claim that they hear something at the same time when there is aurora in the sky. We are aware of only one case where a microphone has been able to detect audible sound associated with aurora (visit Auroral Acoustics: the web site does not have sound samples, but you'll find a link to an in-depth paper and recent news on this topic.). The sound is often described as whistling, hissing, bristling or swooshing. What it is that gives people the sensation of hearing sound during auroral displays is an unanswered question. By searching for an answer to that question, we will probably learn more about the brain and how sensory perception works than about the aurora.

Can you predict when and where there will be aurora?
 
What is the solar wind?
Streams of charged particles that produce the aurora come from the corona, the outermost layer of the sun's atmosphere. The corona is exceedingly hot, measuring more than one million degrees. The high temperature causes hydrogen atoms to split into protons and electrons. The resulting gas of charged particles is called plasma, which is electrically conductive. The solar plasma is so hot that it breaks free of the sun's gravitational force and blows away from the surface in all directions. The movement of this plasma is called solar wind. The intensity of the solar wind and the magnetic field carried by it change constantly. When the solar wind blows stronger, we see more active and brighter aurora on Earth. 
What is the 11-year solar cycle?
What are Kp numbers?

 

 

 

 

下面是极光的形状。我回顾了一下先生拍的照片,好像几种形状都有。 

 

[ 打印 ]
阅读 ()评论 (18)
评论
PeonyInJuly 回复 悄悄话 回复 'tiger00' 的评论 : 谢谢小虎妹妹分享网站。 我去看了一眼, 需要多研究才能看懂。 祝你在不久的将来看到极光爆发!
tiger00 回复 悄悄话 我跟看了这个网站:https://twitter.com/_SpaceWeather_
G1是KP5,应该说春秋季节我跟看了,太阳爆发强的时候安省有时也可以看到。
极光是一定要看的,不看终身遗憾。
收藏您的网站了,好好跟读。谢谢!
PeonyInJuly 回复 悄悄话 回复 'xiaxi' 的评论 : 好的遐西,我一定知无不言,言无不尽。
xiaxi 回复 悄悄话 看北极光是我一直的梦想。以后去阿拉斯加前要到你这里来咨询。
PeonyInJuly 回复 悄悄话 回复 '暖冬cool夏' 的评论 : 暖冬你太可爱了! 今生如果想 就一定能看上。 你那么爱大自然,估计你体验到极光爆发的时候,一定比我更激动,感触更丰富。
还有四五年可以准备,2025年可以考虑哦。
暖冬cool夏 回复 悄悄话 今年是最不活跃的年份,上次看到你回复的留言,最后写得很有激情,你的转变对我很有触动。不过不知道今生会不会去看:)
PeonyInJuly 回复 悄悄话 回复 'Zucker' 的评论 : 是的。很多因素影响。多伦多附近能看到,那天一定是特别强的爆发。运气真好!
Zucker 回复 悄悄话 极光强度、爆发时间、天气和月光都是比较关键的参数,我是在多伦多附近看到过一次,那次这几个参数都极佳。
PeonyInJuly 回复 悄悄话 回复 'iceox' 的评论 : 谢谢来访。 冬假春假都是不错的选择。 春假可能会稍微暖和些,而且日照长。
iceox 回复 悄悄话 静等民宿,极光是一直都想看的,不过现在一定要跟据女儿学校时间,所以我们只能在冬假,新年时 看
PeonyInJuly 回复 悄悄话 回复 'BeijingGirl1' 的评论 : 谢京妞!新周愉快!
PeonyInJuly 回复 悄悄话 回复 '兵团农工' 的评论 : 谢谢来访和留言。
PeonyInJuly 回复 悄悄话 回复 '笑薇.' 的评论 : 太感谢了!又为我解一个大惑!感谢笑薇的留言。下次我也可以这样跟别人解释了。
“极光是气体,液体,固体以外的第四种物质状态,等离子体。”
PeonyInJuly 回复 悄悄话 回复 'tiger00' 的评论 : 谢谢分享。4月29-8月21号应该看不到的,因为那段时间没有黑夜。
G2 是啥?您是开车去哪个城市看的?下次我分享一下如何跟踪webcam追光。
关于民宿/酒店的选择,我也想写写。一两天就写。
BeijingGirl1 回复 悄悄话 好文章。 很多信息。 收藏了。
兵团农工 回复 悄悄话 二月二十二至二十四日在黄刀看极光,ok
笑薇. 回复 悄悄话 极光是气体,液体,固体以外的第四种物质状态,等离子体。
tiger00 回复 悄悄话 谢谢介绍,我去年4-9月都一直跟着网站看,有2次G2还开车出去,都没看到。
今年还会跟,我和先生的 bucket list,一定要去看一次,我一直跟 space weather 网站,如果今年是低谷,也许明年再去,您开民宿,到时可以找您连续住宿等等吗?
登录后才可评论.