Other
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsm41b1726m&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #SM41B-1726
Other
[0310] Atmospheric Composition And Structure / Airglow And Aurora
Scientific paper
The proton auroras have significant differences from electron auroras in their spectral shape. They show Doppler-shifted and broadened spectra: the spectra have Doppler-shifted (~0.5 nm shorter) peak and both bluewing (~2-4 nm) and redwing (~1.5 nm) extending. Energy spectra of precipitating protons have been estimated from this shape. Recently it is found that the intensity in the extent of the blue wing reflects more effectively by the change of the mean energy of precipitating protons than the shift of peak wavelength [Lanchester et al., 2003]. Another character of the H-beta aurora is that it is diffuse form because a proton becomes hydrogen atom due to a charge-exchange reaction with atmospheric constituent and then possible to move across the magnetic field line. By using a scanning photometer, the movement of the proton auroral belt and change of a spectrum shape associated with the variation of proton source region due to storm and substorm were reported, however, not discussed in detail yet [Deehr and Lummerzheim, 2001]. The purpose of this study is to obtain the detail characteristics of H-beta aurora for understanding of source region of energetic protons in the magnetosphere. For this purpose, a new meridian-scanning photometer (SPM) was installed at Husafell station in Iceland in last summer season and Syowa Station, Antarctica. It will contribute to investigate the distribution of energetic protons and plasma waves which cause the pitch angle scattering in the magnetosphere. The meridian-scanning photometer is able to observe at five wavelengths for H-beta emission. One channel is to measure the background level. By analyzing the data obtained by the SPM, the H-beta spectrum can be estimated by fitting a model function with it. Then it is possible to obtain distribution of precipitating protons in north-south direction. It is also possible to estimate an energy spectrum of precipitating proton, simultaneously. The instrumental parameters of the SPM is defined by the transmission characteristics of the interference filters; they are 485.7 nm (FWHM: 3.0 nm), 484.5 nm (0.6 nm), 485.5 nm (0.6 nm), 486.5 nm (0.6 nm) and 487.5 nm (0.6 nm) for H-beta auroras, and OI 630 nm (0.6 nm), N_2 1PG 670.5 nm (5.0 nm) and OI 844.6 nm (0.6 nm) for electron auroras. We analyzed the event at 2100 UT 23rd June, 2009 observed at Syowa station. This is typical auroral breakup event. And in this event, breakup occurred in FOV of the photometer and expanded to poleward. Then NS aurora appeared and pulsating aurora occurred. We calculated Doppler profile and each parameter is below. The peak intensity is 80 R/nm, wavelength at peak intensity is 486.0 nm, HWHM of bluewing is 1.7 nm and HWHM of redwing is 0.9 nm. These value are within past studies, although the Doppler shift of peak intensity is 0.1 nm and shorter than the average of past studies (0.5 nm). And intensity and Doppler profile of proton aurora changed with eqatorward moving in substorm growth phase. This suggests that the source of precipitating proton moves Earthward and its energy increases, and correspond to the result of Deehr and Lummerzheim, 2001. We are going to report the more detailed result of this event and new events of proton aurora.
Kadokura Akira
Mochizuki Takuro
Ono Takafumi
Sato Naoko
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