@article{oai:nipr.repo.nii.ac.jp:00002150,
 author = {Hirasima, Yo and Murakami, Hiroyuki and Nakamoto, Atsushi and Okudaira, Kiyoaki and Suzuki, Hiromu and Yamagami, Takamasa and Ohta, Shigeo and Namiki, Michiyoshi and Nishimura, Jun and Miyaoka, Hiroshi and Sato, Natsuo and Fujii, Ryoichi and Kodama, Masahiro},
 journal = {Memoirs of National Institute of Polar Research. Special issue},
 month = {Mar},
 note = {P(論文), A balloon observation of auroral X-rays has been carried out by using two kinds of X-ray imagers, i.e., a newly developed imager with 5×5 matrix array of Si(Li) semiconductor detectors (SSD's) and another one with one-dimen-sional array of 8 NaI (Tl) scintillation counters. Each of these two imagers has a pinhole collimator, which gives a resolution angle of 15°at the central detector (counter). The lower limits of X-ray energy measurable are 37 and 22keV for the SSD and NaI(Tl) imagers, respectively. The balloon carrying these imagers was launched from Abelver, Norway at 2117 UT on July 5,1985 and was flown toward lceland. An enhancement of auroral X-ray flux was observed in the location of L=5.2 at ∿ 2334 MLT near the geomagnetic midnight, during a geomagnetic substorm. Temporal variation of two-dimensional auroral X-ray images was derived with 3 s time resolution from SSD imager data. Also, another imager of NaI(Tl) counters confirmed the SSD results. It is shown that a sequence of auroral X-ray images obtained by two imagers are not like a stable arc structure but a localized structure with a rapid time variation. The present results suggest that localized intermittent precipitations of energetic electrons with several tens keV or greater are possible.},
 pages = {44--55},
 title = {A balloon observation of auroral X-ray images in the northern auroral zone},
 volume = {47},
 year = {1987}
}