Calculations and ground-based observations of pulsed proton events in the dayside aurora

Sigernes, F.; Fasel, G. J.; Minow, Joseph I.; Deehr, C. S.; Smith, Roger W.; Lorentzen, D. A.; Wetjen, L.T; Henriksen, K.

doi:10.1016/0021-9169(95)00113-1

Cited by 15 publications

(16 citation statements)

References 24 publications

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“…The Balmer decrement, defined as the ratio of the total brightness of the H α to H β lines in proton aurora, has been the focus of both experimental and theoretical studies for the last 40 years [e.g., Eather , 1967; Rees , 1982; Van Zyl et al , 1984; Srivastava and Singh , 1987; Sigernes et al , 1994a, 1994b; Sigernes et al , 1996, and references therein]. This ratio could, in principle, yield information on the spectral characteristics of the incoming protons [ Sigernes et al , 1996].…”

Section: Introductionmentioning

confidence: 99%

Spectral imaging of proton aurora and twilight at Tromsø, Norway

et al. 2004

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[1] An imaging Echelle spectrograph designed for high-resolution studies of selected spectral features located in the visible spectrum was deployed from November 2001 until April 2003 in Tromsø, Norway. For moderately disturbed magnetic conditions, Tromsø is located on the equatorial edge of the evening auroral oval for several hours. Energetic protons are frequently the dominant particle energy source in this region. For this experiment, four spectral windows were selected, each around different emission features: H a (656.3 nm), H b (486.1 nm), N 2 + 1NG 427.8 nm, and OI 777.4 nm. The 8°long slit of the spectrograph was centered on the magnetic zenith. This instrument provided simultaneous, high-resolution ($0.1 nm) spectra of H a and H b emissions, which offers a unique opportunity to investigate the H a to H b Balmer decrement in proton aurora. Information on the cloud cover and on the overall auroral activity was provided by a large field of view (70°) conventional imaging spectrograph that spans the 350-800 nm spectral range. In this paper we describe both instruments and demonstrate their capabilities for the study of the H Balmer emissions in twilight and during auroral activity. Our high-resolution spectra taken in twilight could be used to observe the variability of the geocoronal component over time and to compare the derived variability with midlatitude sites. We conclude that the 0.1 nm spectral resolution is sufficient to identify and take into account contaminating OH and N 2 1PG features in H a emission profiles. Comparison of H b Doppler profiles observed at different locations (Tromsø, Poker Flat, Svalbard) in proton aurora is presented. Lummerzheim and Galand [2001] find that the shape of the violet wing of the Balmer profile is a more suitable indicator of the mean energy of the incident protons than the Doppler shift of the peak. Numerous uncertainties in measured and modeled H a and H b line profiles preclude using the Balmer decrement as an indicator of the precipitating proton flux.

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Section: Introductionmentioning

confidence: 99%

Spectral imaging of proton aurora and twilight at Tromsø, Norway

et al. 2004

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“…From the exit slit, a light pipe ducts the light to a thermoelectricallycooled GaAs photomultiplier tube that has a nearly uniform spectral response across the wavelength region of interest. Both spectrometers have a field of view of 4-5 • along the entrance slit and are aligned to the local magnetic zenith, which is approximately 8 • south of geographic zenith in the magnetic meridian plane [26].…”

Section: Optical Instrumentsmentioning

confidence: 99%

Dual site observations of dayside Doppler-shifted hydrogen profiles: preliminary results

Holmes¹,

Kozelov²,

Sigernes³

et al. 2008

Can. J. Phys.

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Simultaneous optical ground-based observations of auroral Balmer excited hydrogen atoms were performed during the boreal winters of 2002-2004 and Longyearbyen, Svalbard (LYR 75.31 • N 111.88 • E geomagnetic). Balmer α (H α ) with a natural wavelength of 6563Å was detected at Ny-Ålesund, while Balmer β (H β ) at 4861Å 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. PACS Nos.: 92.60.hw 94.20.Ac, 94.30.Aa Résumé : Nous avons effectué simultanément du sol des mesures optiques de l'excitation Balmer des atomes d'hydrogène dans des aurores boréales, pendant les hivers nordiques 2002-2003 et 2003-2004 à Ny-Ålesund, Svalbard (NYA 76.26 • N 110.98 • E géomagnétique) et à Longyearbyen, Svalbard (LYR 75.31 • N 111.88 • E géomagnétique). On a détecté la ligne Balmer α (H α ) de longueur d'onde 6563Å à Ny-Ålesund et la ligne Balmer β (H β ) de 4861Å à Longyearbyen. Nous savons que ces émissions proviennent d'une précipitation de protons qui cause un échange de charges dans l'atmosphère neutre, formant une zone d'émission diffuse avec déplacement Doppler. Les mesures utilisent des spectromètres EbertFastie séparés de 118 km sur une ligne de longitude géomagnétique à peu près constante, ce qui en fait une configuration appropriée à l'étude de la variation de l'énergie des protons avec la latitude géomagnétique, le soi-disant effet de filtre de vitesse. Dans le but de réduire les incertitudes sur les énergies mesurées à partir du profile Doppler, nous avons évalué nos différences en énergie en utilisant l'entière période de temps du phénomène pour chaque cas (jusqu'à 2 h).[Traduit par la Rédaction]

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“…As such, MSP measurements provide a crucial context on the latitude extent of the proton and electron aurora (e.g. Sigernes et al, 1996a;Deehr et al, 1998;Lorentzen and Moen, 2000;Lanchester et al, 2003). Photometric observations around auroral emissions including H emissions have also been used in support of rocket campaigns aimed at proton aurora studies to facilitate the launch decision and provide auroral context and conditions along the flight path (e.g.…”

Section: Scientific Achievementsmentioning

confidence: 99%

“…A profile was acquired every 16 s, but up to 15 scans are averaged together to improve the signal-to-noise ratio, yielding a time resolution of 4 min. Two EFS (0.5 and 1 m) measuring near H a or H b have been used for observing proton aurora from Svalbard (Sigernes et al, 1996a;Deehr et al, 1998;Lorentzen et al, 1998). For a 1 mm slit, the FWHM of the H Balmer spectrograph is between 0.2 and 0.6 nm.…”

Section: Instruments and Techniquesmentioning

confidence: 99%