科研之友
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摘要
Simultaneous optical ground-based observations of auroral Balmer excited hydrogen atoms were performed during the boreal winters of 2002-2003 and 2003-2004 at Ny-angstrom lesund, Svalbard (NYA 76.26 degrees N 110.98 degrees E geornagnetic) and Longyearbyen, Svalbard (LYR 75.31'N 11 1.88'E geomagnetic). Balmer alpha (H-alpha) with a natural wavelength of 6563A was detected at Ny-Alesund, while Balmer beta (H-beta) at 4861 angstrom was measured at Longyearbyen. The emissions are well known to originate from precipitating protons whose charge exchanges with the neutral atmosphere lead to a diffuse, Doppler-shifted emission region. Measurements are made using Ebert-Fastie spectrometers that are located 118 km apart on a line of roughly constant geomagnetic longitude, thus making this configuration suitable for studying the variation of proton energy with geomagnetic latitude, the so-called "velocity filter" effect. For two different days, analysis of the spectrometer data sets was performed, yielding in both cases positive energy differences between LYR and NYA in support of the velocity filter concept. To reduce uncertainties in the determined energies obtained from the Doppler profile, distributions of energy difference were constructed using the entire time period (up to 2 h) for each case.
- 出版日期2008-5
