A model based method for obtaining the open/closed field line boundary from the cusp auroral 6300 Å[OI] red line

Johnsen, Magnar Gullikstad; Lorentzen, D. A.; Holmes, J. M.; Løvhaug, U. P.

doi:10.1029/2011ja016980

Cited by 19 publications

(41 citation statements)

References 85 publications

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“…See their work for a thorough discussion on mapping heights, errors and the use of MSP data for cusp auroral studies. Johnsen et al [2012]shows that the OCB as obtained from the energetic particle instrumentation onboard the NOAA‐16 satellite fits well within the calculated uncertainties of the MSP method.…”

Section: Data Processing and Resultssupporting

confidence: 59%

A statistical analysis of the optical dayside open/closed field line boundary

Johnsen¹,

Lorentzen²

2012

J. Geophys. Res.

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[1] In the cusp, the equatorward boundary of the auroral 6300 Å[OI] red line emission can be used as a proxy for the dayside open/closed field line boundary (OCB). In this paper we perform a statistical study based on ground-based optical data from Longyearbyen, Svalbard, covering a period of 15 auroral seasons from 1995 to 2009 (northern hemisphere, winter conditions), concentrating on the time period close to magnetic noon in the dayside part of the auroral oval. Acquiring the OCB latitude from these data, we have compared it to a variety of solar wind coupling functions and geomagnetic indices. The OCB is, according to our findings, located at 75.4 degrees MLAT. The diurnal movement of the OCB latitude follows the poleward edge of the Feldstein auroral oval, confirming the notion that its poleward part is on open field lines. A causal relationship between the latitudinal location of the OCB and the solar cycle is demonstrated. A dependency is clearly seen between the negative Bz component of the interplanetary magnetic field and the OCB latitude. However, when plotting the OCB latitude as function of coupling functions where the solar wind velocity also is taken into account, better correlations are obtained. We are in this work not able to find previously used coupling functions that clearly distinguishes themselves from the others with respect to correlation coefficients. Good correlations with geomagnetic indices such as AE, PC and SYM/H, suggests that both processes at the magnetopause and in the magnetotail are needed in order to best understand the latitudinal location of the dayside OCB.

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Section: Data Processing and Resultssupporting

confidence: 59%

A statistical analysis of the optical dayside open/closed field line boundary

Johnsen¹,

Lorentzen²

2012

J. Geophys. Res.

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“…It was placed in a 1000 km × 46 000 km orbit around the Earth, with an inclination of 90 • (passing over the poles). Onboard of IM-AGE, the far ultraviolet (FUV) imaging system instrument employs three detectors, among which the Wideband Imaging Camera (WIC) is designed to view the whole Earth and the auroral oval at satellite distances greater than 4 R E (Frey et al, 2001 (Johnsen et al, 2012). Figure 10 presents an example from 17 March 2007, when CHAMP and DMSP F15 flew across the northern polar region almost at the same time.…”

Section: Comparison With Dmsp Image and Msp Observationsmentioning

confidence: 99%

“…The emission was mapped to MLat using an altitude of 268 km. This corresponds to the peak altitude of the reference cusp aurora defined by Johnsen et al (2012), which is based on precipitation characteristics and atmospheric and ionospheric conditions considered by them to be close to average. The open-closed field line boundary (OCB) deduced from optical features is indicated as a solid black line, with error margins indicated by dashed black lines.…”

Section: Comparison With Dmsp Image and Msp Observationsmentioning

confidence: 99%

Determining the boundaries of the auroral oval from CHAMP field-aligned current signatures – Part 1

et al. 2014

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Abstract. In this paper we present the first statistical study on auroral oval boundaries derived from small-and mediumscale field-aligned currents (FACs, < 150 km). The dynamics of both the equatorward and poleward boundaries is deduced from 10 years of CHAMP (CHAllenging Minisatellite Payload) magnetic field data (August 2000-August 2010). The approach for detecting the boundaries from FACs works well under dark conditions. For a given activity level the boundaries form well-defined ellipses around the magnetic pole. The latitudes of the equatorward and poleward boundaries both depend, but in different ways, on magnetic activity. With increasing magnetic activity the equatorward boundary expands everywhere, while the poleward boundary shows on average no dependence on activity around midnight, which seems to be stationary at a value of about 72 • Mlat. Functional relations between the latitudes of the boundaries and different magnetic activity indices have been tested. Best results for a linear dependence are derived for both boundaries with the dayside merging electric field. The other indices, like the auroral electrojet (AE) and disturbance storm time (Dst) index, also provide good linear relations but with some caveats. Toward high activity a saturation of equatorwards expansion seems to set in. The locations of the auroral boundaries are practically independent of the level of the solar EUV flux and show no dependence on season.

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“…In a previous paper (Lilensten et al 2006), prevision, it was foreseen that the angle of polarization should be perpendicular to the line of sight when looking perpendicular to the magnetic field. Morever, 210 km corresponds to the altitude where the red line is expected to be the most intense (Johnsen et al (2012) and reference therein). During the following campaigns, we were able to demonstrate that a southward or a parallel to the magnetic field (B) pointing reduces drastically the degree of linear polarization (Barthélemy et al 2011).…”

Section: Introductionmentioning

confidence: 99%

The thermospheric auroral red line polarization: confirmation of detection and first quantitative analysis

Lilensten

Barthélemy

Amblard

et al. 2013

J. Space Weather Space Clim.

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The thermospheric atomic oxygen red line is among the brightest in the auroral spectrum. Previous observations in Longyearbyen, Svalbard, indicated that it may be intrinsically polarized, but a possible contamination by light pollution could not be ruled out. During the winter 2010/2011, the polarization of the red line was measured for the first time at the Polish Hornsund polar base without contamination. Two methods of data analysis are presented to compute the degree of linear polarization (DoLP) and angle of linear polarization (AoLP): one is based on averaging and the other one on filtering. Results are compared and are in qualitative agreement. For solar zenith angles (SZA) larger than 108°(with no contribution from Rayleigh scattering), the DoLP ranges between 2 and 7%. The AoLP is more or less aligned with the direction of the magnetic field line, in agreement with the theoretical predictions of Bommier et al. (2010). However, the AoLP values range between ±20°around this direction, depending on the auroral conditions. Correlations between the polarization parameters and the red line intensity I were considered. The DoLP decreases when I increases, confirming a trend observed during the observations in Longyearbyen. However, for small values of I, DoLP varies within a large range of values, while for large values of I, DoLP is always small. The AoLP also varies with the red line intensity, slightly rotating around the magnetic field line.

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A model based method for obtaining the open/closed field line boundary from the cusp auroral 6300 Å[OI] red line

Cited by 19 publications

References 85 publications

A statistical analysis of the optical dayside open/closed field line boundary

A statistical analysis of the optical dayside open/closed field line boundary

Determining the boundaries of the auroral oval from CHAMP field-aligned current signatures – Part 1

The thermospheric auroral red line polarization: confirmation of detection and first quantitative analysis

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