地球大氣受到宇宙射線、太陽輻射、X-ray等高能輻射照射與放射性物質對空氣的游離，產生正離子、負離子，使大氣中含有少量的電荷可以流動形成大氣導電率。而大氣導電率會隨著不同高度、時間、溫濕度、氣溶膠濃度等有所變化，現今也有許多研究指出地震發生的前後可能導致地表大氣導電率的改變。且透過大氣導電率與大氣電場的量測，便可推導出大氣垂直電流密度，此參數對於全球大域電路中電荷流動的機制是不可或缺的。因此大氣導電率的量測是非常重要的。
本論文將針對傳統的吉爾定電容器(Gerdien condenser)進行改良，發展雙管型吉爾定電容器作為大氣導電率量測儀器。本儀器採用不同的同軸管供電方式避免靜電透鏡(Electrostatic lens)的產生，並且透過兩個同軸管進行同時量測，排除冷次定律所造成的量測誤差。並經由負離子產生器與不同空氣密度下的定性測試後，本儀器可有效量測於不同離子濃度下之導電率變化。
最後將儀器移至戶外進行長時間的現地量測，發現大氣導電率在晴朗天氣下會隨著日夜有所化，而在陰天時有明顯上升的趨勢。且在本次量測過程中經歷了一場地震，也量測到了較高的大氣導電率。

The air molecules in the Earth's atmosphere can be ionized by cosmic rays, solar high-energy radiation, and radioactive materials. These free charged particles are the source of the atmospheric electric conductivity. The conductivity of the atmosphere varies with altitudes, local times, temperature, humidity, and aerosol concentration, etc. Nowadays, many studies pointed out that the atmosphere conductivity may manifest a significant change before or after earthquakes. The atmospheric vertical current density can be inferred by measuring the atmospheric conductivity and vertical electric field simultaneously, and this parameter is essential for the charge circulation in the global electrical circuit model. Therefore, the measurement of atmospheric conductivity is very important.
In this study, a double-tube Gerdien condenser is developed based on the design of the traditional Gerdien condenser as an atmospheric conductivity measurement instrument. The instrument has new improvements to prevent the bias caused by the electrostatic lens. Furthermore, simultaneous measurement by two sets of coaxial tubes eliminates the voltage-switching surges. After functional tests, the double-tube Gerdien condenser is confirmed to be able to measure the atmospheric conductivity effectively.
Finally, double-tube Gerdien condenser measured a long-term air conductivity trend in an outdoor environment. It was found that the atmospheric conductivity is driven by several factors such as diurnal variation, human activities, and rainfall. In addition, a higher atmospheric conductivity was also identified when an earthquake occurred during this measurement.

Burt, D. A. (1967), The Development of a Gerdien Condenser for Sounding Rockets, Upper Air Research Laboratory, University of Utah, Scientific Reprot No. 8.
Gerdien, H. (1905), Demonstration eines Apparates zur absoluten Messung der electrischen Leitfáhigkeit der Luft, Phys. Z. 6: 800 – 801.
Gish, O. H. (1944), Evaluation and interpretation of the columnar resistance of the atmosphere. Journal of Geophysical Research, 49(3), 159-168.
Gish, O. H. (1951), Universal aspects of atmospheric electricity, In Compendium of Meteorology, edited by T. F. Malone, American Meteorological Society, Boston, 101-119.
Harrison, R. G. (2004), The global atmospheric electrical circuit and climate, Surveys in Geophysics, 25, 441-484.
Kamsali, N., B. S. N. Prasad, and J. Datta (2009), Atmospheric electrical conductivity measurements and modeling for application to air pollution studies, Advances in Space Research, 44, 1067-1078.
Kuo, C. , Ho, Y. and Lee, L. (2018), Electrical Coupling Between the Ionosphere and Surface Charges in the Earthquake Fault Zone, In Pre‐Earthquake Processes (eds D. Ouzounov, S. Pulinets, K. Hattori and P. Taylor), doi:10.1002/9781119156949.ch7
Riggio, A., and M. Santulin (2015), Earthquake forecasting: A review of radon as seismic precursor, Boll. Geofis. Teorica. Appl., 56(2), 95– 114, doi:10.4430/bgta0148.
Rosen, J. M., D. J. Hofmann, W. Gringel, J. Berlinski, S. Michnowski, Y. Morita, T. Ogawa, and D. Olson (1982), Results of an International Workshop on Atmopheric Elecrical Measurements, J. Geophys. Res., 87, 1219-1227.
Roubal, Z., Bartusek, K., Szabo, Z., Drexler, P., & Uberhuberova, J. (2017), Measuring light air ions in a speleotherapeutic cave, Measurement Science Review,17(1), 27–36.
Rycroft, M. J., and R. G. Harrison (2011), Electromagnetic atmosphere-plasma coupling the global atmospheric electric circuit., Space Sci. Rev., doi:10.1007/s11214-011-9830-8.
Siingh, D., Singh, R. P., Kamra, A. K., Gupta, P. N., Singh, R., Gopalakrishnan, V., & Singh, A. K. (2005) Review of electromagnetic coupling between the Earth's atmosphere and the space environment. Journal of atmospheric and solar terrestrial physics, 67(6), 637-658.
Singh, D. K., Singh, R. P., & Kamra, A. K. (2004),The electrical environment of the Earth’s atmosphere: A review. Space Science Reviews, 113(3-4), 375-408.
Swann, W. F. G. (1914), The theory of electrical dispersion into the free atmosphere, with a discussion of the theory of the Gerdien conductivity apparatus, and of the theory of the collection of radioactive deposit by a charged conductor, J. Terr. Mag. Atmos. Elect., 19, 81-92.
Thomson, J. J. (1928), Conduction of electricity through gases, 3rd edition, Cambridge University Press.
Woessner, R. H., W. E. Cobb, and H. Gunn (1958), Simultanenous measurements of the positive and negative light-ion conductivities to 26 km, J. Geophys. Res., 63, 171-180.
王宜傑(2019)，「自動化地表電場計研製與應用」，國立成功大學太空與電漿科學研究所碩士論文。
何旻潔(2018)，「高時間解析度地表導電率量測」，國立成功大學太空與電漿科學研究所碩士論文。
邱泰瑋(2017)，「使用探空氣球量測對流雲中的電荷垂直分布」，國立成功大學太空與電漿科學研究所碩士論文。
莊嘉文(2020)，Private communication.
葉爾君(2018)，「劇烈天氣與地震之地表垂直電場變化」，國立成功大學太空與電漿科學研究所碩士論文。
賴炫禎(2018)，「發展吉爾定電容器用於大氣導電率量測」，國立成功大學太空與電漿科學研究所碩士論文。