Solar Wind (太陽風) 什麼是太陽風？

Presentation on theme: "Solar Wind (太陽風) 什麼是太陽風？"— Presentation transcript:

1 Solar Wind (太陽風) 什麼是太陽風？
我們所知的太空其實並非是真空，在地球附近每立方公分約有10個質點，而且是帶電質點。這些帶電質點來自於我們的太陽 從日冕 洞吹來的太陽風。太陽風的速率在地球附近每秒約400 公里。 誰提出太陽風的概念？ 柏克(Parker)在1958 年提出有名的太陽風理論。太陽隨時有高速的電漿放出而充滿於行星際空間，也就是所謂的太陽風。柏克並算出，如果太陽附近的日冕溫度若是一百萬度時，則在距離太陽1AU 的地球附近地區，太陽風的速率是500 公里/ 秒及密度是每立方公分有七個質子或電子。1962 年，美國的水手二號太空船，證實了柏克的理論是正確的。

2 Solar Wind (太陽風) 太陽風中不但有電漿，而且太陽表面的磁埸亦為其所帶出，即所謂的
行星際空間磁埸(IMF)。太陽在旋轉，在赤道附近自轉一周約為地球的 25 天，而兩極則是35 天左右。在太陽表面不同部份會放射出不同速度 的太陽風。當太陽風吹出時，磁場會被太陽風拉著跑，由於太陽的自 轉，太陽磁場會以螺旋結構分佈於太陽系當中，此一太陽磁場又會與 太陽系行星的磁場相互影響而造成多個行星附近之太空天氣變化。

3 太陽對地球太空天氣的影響 太陽的爆發是所有太空天氣現象的主要來源， 太陽風夾帶著這些效應到地球時，會與地球
磁場作用而影響磁層與電離層，同時引發的 磁層與電離層之電漿耦合作用也很重要。整 個作用鏈從太陽直到地球觀測到的磁暴，這 包含著相當複雜的過程，而星際宇宙射線 (galactic cosmic rays)也被視為傷害的次要來源。

4 太空天氣對地球太空環境各層面的影響 ... disrupted by solar and geomagnetic events
Satellite operations (衛星操作) Space Shuttle and Space Station activities (太空任務) High-altitude polar flights (高緯極地飛航) Railway (鐵路交通) Navigation (航海) HF radio communications (高頻通信) Mobile phone communications (行動電話通信) Electric power distributions (電力配送) Pipeline operations (油氣輸送) Long Term Climate Variations (長期氣候變動) cardiovascular disease incidence (心血管疾病發病率)

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7 (Adapted from : Joe H. Allen, SCOSTEP, GOMAC 2002)
Joe Allen: Phantom Command (PC) is the descriptive name given to the type of anomaly in which a satellite instrument “turns on” when it should be “off”, or the reverse, as if a command was received out of the planned sequence from some phantom ground controller. Such anomalies may be only a nuisance to satellite operators, or they may impair the operation of systems vital to satellite function. They are often seen clustered in sectors of a GEO satellite orbit, such as the “midnight-to-dawn” region (see following slides). Also, they are often clustered bi-modally by season, with the peak happening in the days before and after each equinox. One aerospace engineer reported a GEO satellite that had its anomalies clustered in the hours neares the dawn and dusk meridian passage. However, they were also clustered by season. It turned out that the satellite had significant thermal electron emission from the large sunlit surface of a continually Earth-pointing main antenna. When the satellite was near dawn and dusk, the antenna was self-shadowing and created a condition in which differential surface charging could occur in the presence of lower energy surplus electrons. The distribution of geomagnetic storms as monitored by the Kp or Ap index shows similar equinoctial peaks to those of the PC satellite anomalies, and represent times when surplus electrons are present. 太空天氣對衛星運作可能造成的影響 False Operations (錯誤動作) : PHANTOM COMMAND PROTON EVENTS (質子事件) Power Panel Output Loss (能源板輸出消失) Charge Deposition(電荷沉降) : SINGLE EVENT UPSETS Arc Discharges(弧狀放電) : Bulk Charging (Deep Dielectric) ION EFFECTS on OPTICAL SENSORS(光學元件受損) Tumbling(衛星翻滾) Pointing Problems(指向問題) : Magnetopause Crossing Events Geomagnetic Storms & Substorms (地磁活動造成的拖曳) : Drag (Adapted from : Joe H. Allen, SCOSTEP, GOMAC 2002)

8 衛星運作異常次數的變化趨勢(恰與太陽活動周期趨勢相符)

9 造成衛星運作被破壞的原因 Electromagnetic Radiation (電磁輻射)
Joe Allen: In order for activity observed on/at the Sun to cause problems for a satellite in interplanetary space, or orbiting Earth inside the magnetosphere, and for technology and humans on Earth or in space, some physical wave or object must reach them from the Sun. These may include: Electromagnetic radiation – light, X-rays, and other wavelengths emitted by the Sun. Energetic particles, especially protons, alphas, and heavier ions from CMEs that expand outward from the Sun in a cloud that eventually may engulf the magnetosphere (or may only slightly graze it or miss it altogether). Successive streams may join together and can form a shock wave that scoops up other plasma in its course. Geomagnetic storms are disturbances at Earth in the otherwise regular daily variations of the geomagnetic field measured by a worldwide array of ground-based magnetic observatories. Such storms arise when a large cloud of electrons penetrate the magnetosphere. They are carried tailward by the broken geomagnetic field lines that merged with the IMS. In the tail, they are injected toward Earth around the midnight meridian in a mass near the equatorial plane. Depending on the sign of their electrical charge, the injected particles are deflected by the geomagnetic field and form a circle of moving charge around Earth (the “ring current”). The dynamic interaction of moving energetic particles and geomagnetic field and induced potentials causes field-aligned currents to flow spiraling down from the equatorial zone at geostationary altitude along field lines to the polar regions where the incoming particles may collide with atmospheric atoms (mainly Oxygen and Nitrogen) and produce the visible aurora, or may rebound for another circuit. Counterpart streams of protons and heavier ions flow in opposite directions from the electrons because of their positive charge. At an altitude of some 100 km, the field-aligned electrons move in E-W flow patterns in the auroral zone, forming the “auroral electrojets”. Polar region magnetic observatories on Earth’s surface record large excursions, especially in H, that vary in amplitude and direction depending on where the station is relative to the overhead current system. These are high latitude disturbances are Auroral Substorms. The equatorial ring current produces a global depression in the H-component of the geomagnetic field. The amplitude of these changes in the geomagnetic field is described and quantified by a variety of magnetic activity indices. Killer Electrons of energy > 2 MeV are recorded by GOES SEM sensors and other geostationary monitoring satellites usually after a the first 24 hours of a recurrent geomagnetic storm. Such increases at GEO altitude may be of two to five orders of magnitude. They can persist for days to weeks, sometimes interrupted for about 24-hours by another low-level magnetic storm. Exposure to these persistent high levels of energetic electrons is associated with satellite bulk charging and consequent arcing which can damage vital satellite elements. 造成衛星運作被破壞的原因 Electromagnetic Radiation (電磁輻射) Flare X-rays and UV affect ionosphere/communications. Energetic particles (ions) (高能粒子) form shock wave, move magnetosphere inside GEO, enhance radiation belts, and cause geomagnetic storms & substorms. Geomagnetic storm (地磁暴) disturbed fields & current systems, surface charging. Auroral Substorm (極光副暴) current systems and fields affect satellites directly. Killer Electrons (殺手電子) increase at GEO after low level magnetic storm, last for weeks.

10 太空飛行 (Space Flight) 太空天氣會影響太空飛行的每個階段，可能因太陽X射線暴(solar X-ray burst)引起的通訊困難而延期，增強的輻射可能傷及太空人而無法太空漫步，未來有人的行星際飛行也需考量配合較低星際宇宙射線(cosmic rays)劑量的時期，以及太陽高能粒子的屏蔽。太空飛船所面臨的危機來源有：熱電漿電子產生的表面充電(surface charging)、高能電子穿透飛船干擾或破壞電子儀器、長時間紫外線造成設備如太陽電池的老化，以及過強紫外線使大氣層向上升展造成衛星在軌道運行的阻力，衛星高度陡降會衛星失去聯絡。

11 航空 (Aviation) 對於飛機駕駛、乘客與機上儀器有威脅的輻射線源為二次宇宙射線(secondary cosmic rays)，飛行路線與高度會關係著影響的程度。因宇宙射線在地磁極區穿透得較深入大氣層，高緯地區的路線有較高的曝曬量，因此科學家正研究該輻射劑量對飛航的影響，歐洲已有飛航的輻射防護法條實施。現代飛機上的微晶片極易受輻射損壞，研究(Ziegler and Srinivasan, 1996)指出飛行高度自9km提高至20km時，儀器上的CMOS的軟錯誤率(soft error rate)將增加一倍。

12 鐵路交通 (Railways) 太空天氣風暴時鐵道設備會因地電場而驅動地磁感應電流(Geomagnetically Induced Currents, GIC)，目前對於GIC產生的電壓大小與影響的相關認知甚少，唯一明確的事件紀錄是1982年7月的磁暴期間，瑞典發生過鐵道號誌自行變成紅燈，但實際並無火車通過，其原因尚不明，但有理由相信一些鐵路設施的誤動作可能與太空天氣有關。

13 航海 (Navigation) 遠洋船舶之間的通信與定位，主要仍依賴穿透或利用電離層反射的通訊系統，此種系統深受太空天氣的影響，電離層特性的改變將導致地面與衛星之間通訊信號衰減或失真，例如全球定位系統(GPS)會因電離層總電子濃度影響其信號傳輸。 低層電離層增加的粒子會吸收在相對高頻處(HF範圍)的短波無線電，造成無線電通訊完全失靈。平常在低處(D、E層)電離層反射出的較低頻率波在此刻會在比平時更低高度反射，而改變傳播途徑。由於此現象會依據太陽所產生的地磁擾動大小和位置而持續數日，因此對無線電通訊的影響格外嚴重。

14 高頻通信 (HF radio communication)
最早發現太空天氣影響電信系統的是150多年前的電報員(Boteler et al.,1998)，當時出現電報機無法操作，有時則不需電池也能操作，因地磁場在通信電纜感應了GIC。1940年3月的大磁暴曾經中斷了北挪威的通訊系統，這次感應的電場強度估計高達45~55V/km，而一般太空天氣引發的電場強度約1~10V/km，因此國際電話的海底電纜可能會感應出上百或上千伏特的電壓。雖然現代的光纜不至於有GIC的問題，但信號放大器仍可能因連接金屬饋線而受GIC影響。

15 通信頻率分布圖(頻率由左而右遞增)

16 太陽無線電波暴與手機行動通信 (Solar Radio Bursts and mobile phone communications)
太陽無線電波暴(solar radio burst)的雜訊會影響通訊，1996年某日美國的行動通信系統電話中斷率因太陽閃焰(solar flare)無線電波輻射由2%增為9%(Lanzerotti et al., 1999)。 Call-blocking bursts can happen as often as once every 3.5 days during solar maximum. This decreases to once in 18.5 days during solar minimum. Consequently, when solar activity is at its maximum, an average base station could be temporarily knocked out several times per year. (Balachandran Bala, Louis J. Lanzerotti, Dale E. Gary, David J. Thompson, "Noise in Wireless Systems Produced by Solar Radio Bursts," Radio Science, Volume. 37, number 2, 2002).

17 電力系統 (Power Grid Systems)
地電場會在電力傳輸網路感應GIC，因GIC是準直流，易造成變壓器飽和。最有名的GIC突發性災難發生於1989年3月加拿大魁北克，該省經歷了數小時的大停電，紐澤西州的一個變電系統也於相同的磁暴中永久損壞。 由於GIC主要在高緯地區造成問題，北美與北歐國家相當關切這方面的研究，但其實GIC也會影響較低緯地區，因為GIC的強度大小取決於系統的結構，亦即傳輸線的阻抗、長度與變壓器的位置，還有一些未知的因素。

18 石油與瓦斯輸送管 (Oil and Gas Pipelines)
地下輸送管若無正確防護容易腐蝕損壞，腐蝕最嚴重的部位在於管路插入周圍土壤之處，在那兒電化學條件會引起腐蝕作用，通常使用高阻抗鍍膜與陰極防鏽系統保護管線，但地磁暴發生時的感應電壓可輕易地超出陰極防鏽電位。位於芬蘭南部的天然氣輸送管未曾因太空天氣而出過問題，即使沿著管線的GIC高達數百安培，因為只要保護鍍膜未破裂，導通電流密度每平方米僅數毫安培。

19 長期氣候變動 (Long Term Climate Variations)
太陽電磁輻射量的變化 太陽電漿與磁場的變動 受控於太陽的宇宙射線量之變化 Adapted form "Solar Activity and Earth's Climate", at Lund Space Weather Center

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21 心血管疾病發病率 (cardiovascular disease incidence)
長期的心臟疾病與腦中風發病率與太空天氣變化的相關性研究指出，在地磁劇烈擾動期間出現較高的發病率，在地磁寧靜期間則有較平常更低的發病率，其他研究也顯示腫瘤之類的病例也與太陽黑子數週期有正相關，這都顯示太空天氣可能影響人體的健康狀態，但這方面仍需更多與更仔細的研究，才能了解其影響性之大小與引發人體反應的機制。 胡漢明、李永生、張文元，太陽活動對腫瘤和循環系統疾病的影響，雲南天文台台刊，No.1, p.35~40, 2000. 曾治權等，北京地區冠心病和腦猝中發病與太陽、地磁活動關係的探討，地理研究，Vol.14, No.3, p.88~95, 1995.

22 太空天氣保險 (Insurance) The market is composed of roughly 12 leading insurers (i.e. insurers  able to study a risk and provide a quotation for it) worldwide, and  roughly 30 "followers" (insurers that will provide capacity behind a leader). 

23 對於太空環境的影響，除了太空天氣因素以外，也有部分來自人為因素所造成，如衛星殘骸所形成的太空垃圾。以下兩圖為太空垃圾在地球上空的分布情形。

24 太空垃圾(Space Garbage, Space Junk)

25 太空垃圾(Space Garbage, Space Junk)