TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 52 (No. 11), pp. 1073-1076, 2000


Characteristics of TEC variations observed at Chofu for geomagnetic storms

A. Yamamoto1, Y. Ohta2, T. Okuzawa2, S. Taguchi2, I. Tomizawa3, and T. Shibata2

1Japan Coast Guard Academy, Kure, Hiroshima 737-8512, Japan
2Department of Information and Communication Engineering, University of Electro-Communications, Chofu, Tokyo 182-8585, Japan
3Sugadaira Space Radio Observatory, University of Electro-Communications, Sugadaira, Nagano 386-2200, Japan

(Received January 14, 2000; Revised May 31, 2000; Accepted August 25, 2000)

Abstract: Since the middle of 1996, we have made a routine observation of TEC using GPS in Chofu (35.65°N, 139.54°E), Tokyo. We examine in this paper the relationship between the perturbation components of TEC and geomagnetic field variations during 11 storm events for 1997-1998 to clarify the mid-latitude characteristics of TEC variations at the time of magnetic storms. The perturbation components of TEC were derived every 20 seconds by subtracting quiet-time TEC values which are estimated as the average of both 3 days just before and after the storm period. The magnetic field data from Memambetsu Magnetic Observatory (45.92°N, 144.20°E) are used for the identification of the storm-time variations. Our results show that (1) the amplitude level of the TEC variation tends to increase during the first 24 hr of storm and then decrease below its usual-day level with recovery in one or two days later for the typical magnetic storm, and (2) during a negative-value phase of the TEC variation, which follows the initial positive hump structure, the perturbation amplitude of TEC shows a remarkable reduction in summer compared to in winter.

Corresponding author E-mail: yamamoto@msa.ac.jp

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