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Spectral imaging of proton aurora and twilight at Tromsø, Norway

Spectral imaging of proton aurora and twilight at Tromsø, Norway
Spectral imaging of proton aurora and twilight at Tromsø, Norway
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? (656.3 nm), H? (486.1 nm), N2+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? and H? emissions, which offers a unique opportunity to investigate the H? to H? 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 N2 1PG features in H? emission profiles. Comparison of H? 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? and H? line profiles preclude using the Balmer decrement as an indicator of the precipitating proton flux.
0148-0227
A07305
Galand, M.
bce54d89-783b-411e-b926-5c803f6a2a31
Baumgardner, J.
1a37df2b-4851-4292-80f8-4b31ccf56d1c
Pallamraju, D.
f0af5286-1376-45c6-8050-b050cee0b3cb
Chakrabarti, S.
d24f1907-514c-42f4-b3ce-285f8c7885e5
Løvhaug, U.P.
5bc61eb4-498e-4bef-8869-28344b9e7b48
Lummerzheim, D.
6432baa4-48ac-4203-bc2d-973de7f3efde
Lanchester, B.S.
e864533e-eea0-471f-a3f9-7c70c25be55b
Rees, M.H.
6ecc0166-51bf-4afd-9471-acbb415fd156
Galand, M.
bce54d89-783b-411e-b926-5c803f6a2a31
Baumgardner, J.
1a37df2b-4851-4292-80f8-4b31ccf56d1c
Pallamraju, D.
f0af5286-1376-45c6-8050-b050cee0b3cb
Chakrabarti, S.
d24f1907-514c-42f4-b3ce-285f8c7885e5
Løvhaug, U.P.
5bc61eb4-498e-4bef-8869-28344b9e7b48
Lummerzheim, D.
6432baa4-48ac-4203-bc2d-973de7f3efde
Lanchester, B.S.
e864533e-eea0-471f-a3f9-7c70c25be55b
Rees, M.H.
6ecc0166-51bf-4afd-9471-acbb415fd156

Galand, M., Baumgardner, J., Pallamraju, D., Chakrabarti, S., Løvhaug, U.P., Lummerzheim, D., Lanchester, B.S. and Rees, M.H. (2004) Spectral imaging of proton aurora and twilight at Tromsø, Norway. Journal of Geophysical Research, 109 (A7), A07305. (doi:10.1029/2003JA010033).

Record type: Article

Abstract

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? (656.3 nm), H? (486.1 nm), N2+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? and H? emissions, which offers a unique opportunity to investigate the H? to H? 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 N2 1PG features in H? emission profiles. Comparison of H? 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? and H? line profiles preclude using the Balmer decrement as an indicator of the precipitating proton flux.

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Published date: 2004

Identifiers

Local EPrints ID: 9124
URI: http://eprints.soton.ac.uk/id/eprint/9124
ISSN: 0148-0227
PURE UUID: 08c6e826-7776-4dbd-88d3-8a395f9958ec

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Date deposited: 21 Sep 2004
Last modified: 15 Mar 2024 04:55

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Contributors

Author: M. Galand
Author: J. Baumgardner
Author: D. Pallamraju
Author: S. Chakrabarti
Author: U.P. Løvhaug
Author: D. Lummerzheim
Author: B.S. Lanchester
Author: M.H. Rees

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