The imaging vector magnetograph at Haleakala

Mickey, D. L.; Canfield, R. C.; Labonte, B. J.; Leka, K. D.; Waterson, M.; Weber, H. M.

doi:10.1007/bf00148052

Cited by 121 publications

(89 citation statements)

References 19 publications

(1 reference statement)

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“…Characteristics of the IVM ("Imaging Vector Magnetograph") at Haleakala, as described by Mickey et al (1996), are equal or below those of THEMIS. Both instruments have the same polarimetric resolution (10 −3 ).…”

Section: Comparison With Other Instrumentsmentioning

confidence: 96%

Vector magnetic field map at the photospheric level below and around a solar filament (neutral line)

Bommier¹,

Rayrole²,

Eff-Darwich³

2005

A&A

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Abstract. We present a vector magnetic field map obtained on 7 December 2003, below and around a filament located not so far from the active region NOAA 517, whose one spot is also found on the map of 240 × 340 arcsec. This region was itself located near the disk center, so that the longitudinal (resp. transverse) field is nearly the vertical (resp. horizontal) one. The THEMIS telescope was used in its spectropolarimetric multiline mode MTR ("MulTiRaies"). The noise level is 5−10 Gauss in the longitudinal field and 50−100 Gauss in the transverse field, while the pixel size is 0.45 arcsec. Fundamental ambiguity is not solved, and the atmosphere is assumed to be homogeneous. The magnetic field derivation method described in this paper was validated on eight test points submitted to the UNNOFIT inversion code, and the results are found in agreement within 14% discrepancy. Two main results appear on the map: (i) a strong spatial correlation between the longitudinal and transverse field resulting in an inclined field vector (making a most probable angle of 60 • or 120 • with the line-of-sight in the filament region); and (ii) homogeneity of the field direction (inclination and azimuth) in the filament region. Parasitic polarities were also detected: first those located at the filament feet, as theoretically expected, on the one hand; and then weak opposite polarity regular patterns that appear between the network field (strong field at the frontiers of supergranules), on the other.The exact superimposition of the magnetic field map derived from the Fe  6302.5 Å line and of the Hα map, which enabled association of the parasitic polarities with the filament feet, was possible because these two maps were simultaneously obtained, thanks to a unique facility available in the multiline mode of THEMIS.

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Section: Comparison With Other Instrumentsmentioning

confidence: 96%

Vector magnetic field map at the photospheric level below and around a solar filament (neutral line)

Bommier¹,

Rayrole²,

Eff-Darwich³

2005

A&A

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“…Here we have created a database of 11 different AR vector magnetograms from the University of Hawaii Imaging Vector Magnetograph (IVM). IVM obtains Stokes images in photospheric lines with 7pm spectral resolution, 1.1 arcsec spatial resolution (∼0.55 arcsec per pixel) over a field of 4.7 arcmin 2 and polarimetric precision of 0.1% (Mickey et al 1996). We used both fully-inverted and quicklook IVM data.…”

Section: Datasetmentioning

confidence: 99%

Simulating flaring events in complex active regions driven by observed magnetograms

Dimitropoulou

Isliker

Vlahos

et al. 2011

A&A

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Context. We interpret solar flares as events originating in active regions that have reached the self organized critical state, by using a refined cellular automaton model with initial conditions derived from observations. Aims. We investigate whether the system, with its imposed physical elements, reaches a self organized critical state and whether well-known statistical properties of flares, such as scaling laws observed in the distribution functions of characteristic parameters, are reproduced after this state has been reached. Methods. To investigate whether the distribution functions of total energy, peak energy and event duration follow the expected scaling laws, we first applied a nonlinear force-free extrapolation that reconstructs the three-dimensional magnetic fields from twodimensional vector magnetograms. We then locate magnetic discontinuities exceeding a threshold in the Laplacian of the magnetic field. These discontinuities are relaxed in local diffusion events, implemented in the form of cellular automaton evolution rules. Subsequent loading and relaxation steps lead the system to self organized criticality, after which the statistical properties of the simulated events are examined. Physical requirements, such as the divergence-free condition for the magnetic field vector, are approximately imposed on all elements of the model. Results. Our results show that self organized criticality is indeed reached when applying specific loading and relaxation rules. Powerlaw indices obtained from the distribution functions of the modeled flaring events are in good agreement with observations. Single power laws (peak and total flare energy) are obtained, as are power laws with exponential cutoff and double power laws (flare duration). The results are also compared with observational X-ray data from the GOES satellite for our active-region sample. Conclusions. We conclude that well-known statistical properties of flares are reproduced after the system has reached self organized criticality. A significant enhancement of our refined cellular automaton model is that it commences the simulation from observed vector magnetograms, thus facilitating energy calculation in physical units. The model described in this study remains consistent with fundamental physical requirements, and imposes physically meaningful driving and redistribution rules.

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“…Photospheric vector magnetograms from the Imaging Vector Magnetograph ("IVM"; Mickey et al 1996;Labonte et al 1999) were used to perform our calculations. The magnetograms were taken at Mees Solar Observatory on Haleakalā, on 14 October 1995, at 00:20 UT and 17:55 UT.…”

Section: Photospheric Magnetic Fieldmentioning

confidence: 99%

Global budget for an eruptive active region

Bleybel¹,

Amari²,

Driel‐Gesztelyi³

et al. 2002

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Abstract. We present results on the magnetic structure of NOAA Active Region #7912 which was involved in a long duration flare on 14 October 1995, and was the source region for a magnetic cloud observed by the WIND spacecraft from October 18-20. Using vector magnetograms from the Imaging Vector Magnetograph ("IVM"), we reconstruct the magnetic field above this active region, assuming it is in a non-linear force-free state. This reconstruction is used to determine global properties of the active region magnetic field including topology, magnetic energy, and relative magnetic helicity. A comparison of some global quantities before and after the eruptive event is discussed. We show that the magnetic energy and relative helicity of the active region decreased after the eruption, consistent with the ejection of a large amount of helicity (in the magnetic cloud). We also show that the relaxed post-flare state still contains nonlinearities and is not consistent with a linear force-free state as predicted by Taylor's theory of relaxation. These results agree with those of recent numerical simulations concerning plasmoid ejection and helicity redistribution in the disruption of magnetic configurations. We propose as an explanation that the anchoring of field lines in the photosphere prevents a full cascade to the Taylor state, and that a variational formulation in which the action functional would describe this constraint should be derived.

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The imaging vector magnetograph at Haleakala

Cited by 121 publications

References 19 publications

Vector magnetic field map at the photospheric level below and around a solar filament (neutral line)

Vector magnetic field map at the photospheric level below and around a solar filament (neutral line)

Simulating flaring events in complex active regions driven by observed magnetograms

Global budget for an eruptive active region

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