Wavelength Dependence of the Helioseismic and Magnetic Imager (HMI) Instrument onboard the Solar Dynamics Observatory (SDO)

Couvidat, S.; Schou, J.; Shine, R. A.; Bush, R. I.; Miles, John W.; Scherrer, P. H.; Rairden, R. L.

doi:10.1007/s11207-011-9723-8

Cited by 112 publications

(108 citation statements)

References 10 publications

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“…SDO spacecraft is located in a geosynchronous, inclined (28.5 • ) orbit, and it completes the orbit in 24 h Schou & Larson 2011;Schou et al 2012;Wachter et al 2012;Couvidat et al 2012). Also, as seen from the ground the spacecraft traces an "eight" spanning 57 degrees in latitude at an altitude of 36 000 km along the meridian 102…”

Section: Sdo/hmi Magnetograms With 45 and 720-s Cadencementioning

confidence: 99%

Artifacts of SDO/HMI data and long-period oscillations of sunspots

Smirnova

Efremov

Parfinenko

et al. 2013

A&A

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Aims. The artifacts of SDO/HMI magnetograms that may affect the low-frequency power spectrum of sunspot oscillations are analyzed. Methods. Several examples are given that present false (artificial) harmonics, which are produced by Doppler shifts in the power spectra of long-period oscillations of sunspots. This arises from peculiarities in the orbital movements of SDO. Results. It was found that those artifacts with periods of 12 and 24 h, as revealed even in variations of weak background magnetic fields, are actually present in SDO/HMI magnetograms. However, the quantitative impact of artifacts remains quite weak and does not change the picture of sunspot oscillations dramatically for as long as the magnetic field in the spot is less than about of 2000 Gauss. When the magnetic field strength is greater than 2000 G, the influence of these artifacts increases sharply to become the dominant factor. One can suggest that the amplification of noise components of these artifacts has a highly nonlinear character with the growth of the magnetic field, and the field strength of about 2000 G then takes on meaning of a threshold value.

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Section: Sdo/hmi Magnetograms With 45 and 720-s Cadencementioning

confidence: 99%

Artifacts of SDO/HMI data and long-period oscillations of sunspots

Smirnova

Efremov

Parfinenko

et al. 2013

A&A

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“…It provides one-arcsecond-resolution full-disk Doppler velocity images and the line-of-sight component of the magnetic field every 45 s . A detailed description of the HMI instrument and the data processing is presented in Schou & Larson (2011, Wachter et al (2012), and Couvidat et al (2012).…”

Section: Sdo/hmi Instrument and Magnetic Field Datamentioning

confidence: 99%

Long quasi-periodic oscillations of sunspots and nearby magnetic structures

Smirnova

Riehokainen

Соловьев

et al. 2013

A&A

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Aims. Simultaneous study of long quasi-periodic oscillations in sunspots (using line-of-sight magnetic field data) and nearby magnetic structures located above them (using radio emission data at 37 GHz) was the basic aim of this work. Methods. Data from the ground-based radio-telescope (Metsähovi Radio Observatory, Aalto University, Finland) and the Helioseismic and Magnetic Imager instrument on-board the Solar Dynamics Observatory spacecraft were obtained and analyzed. We used the wavelet (Morlet) analysis and the fast Fourier transform (FFT) method to obtain the oscillation periods. Results. Long-period oscillations in intervals of 200-400 min were found both in radio and in magnetic field data. The interpretation of these oscillations and their propagation to higher levels of the solar atmosphere are discussed in the context of a "shallow sunspot" model.

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“…The discussion of the temporal evolution and morphology of the active region NOAA 11126 is based on full-disk images and line-of-sight (LOS) magnetograms obtained with the Helioseismic and Magnetic Imager (HMI, Schou et al 2012;Couvidat et al 2012;Wachter et al 2012) on board the Solar Dynamics Observatory (SDO). Since the Hinode FOV is too small to cover the entire active region and provide an overview of the magnetic field topology, we show in Fig.…”

Section: Sdo/hmi Full-disk Imagesmentioning

confidence: 99%

Horizontal flow fields observed in Hinode G-band images

Verma

Balthasar

Deng

et al. 2012

A&A

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Context. Generation and dissipation of magnetic fields is a fundamental physical process on the Sun. In comparison to flux emergence and the initial stages of sunspot formation, the demise of sunspots still lacks a comprehensive description. Aims. The evolution of sunspots is most commonly discussed in terms of their intensity and magnetic field. Here, we present additional information about the three-dimensional flow field in the vicinity of sunspots towards the end of their existence. Methods. We present a subset of multi-wavelengths observations obtained with the Japanese Hinode mission, the Solar Dynamics Observatory (SDO), and the Vacuum Tower Telescope (VTT) at Observatorio del Teide, Tenerife, Spain during the time period 2010 November 18−23. Horizontal proper motions were derived from G-band and Ca ii H images, whereas line-of-sight velocities were extracted from VTT echelle Hα λ656.28 nm spectra and Fe i λ630.25 nm spectral data of the Hinode/Spectro-Polarimeter, which also provided three-dimensional magnetic field information. The Helioseismic and Magnetic Imager on board SDO provided continuum images and line-of-sight magnetograms, in addition to the high-resolution observations for the entire disk passage of the active region. Results. We perform a quantitative study of photospheric and chromospheric flow fields in and around decaying sunspots. In one of the trailing sunspots of active region NOAA 11126, we observe moat flow and moving magnetic features (MMFs), even after its penumbra had decayed. We also detect a superpenumbral structure around this pore. We find that MMFs follow well-defined, radial paths from the spot all the way to the border of a supergranular cell surrounding the spot. In contrast, flux emergence near the other sunspot prevents the establishment of similar well ordered flow patterns, which could be discerned around a tiny pore of merely 2 Mm diameter. After the disappearance of the sunspots/pores, a coherent patch of abnormal granulation remained at their location, which was characterized by more uniform horizontal proper motions, low divergence values, and smaller photospheric Doppler velocities. This region, thus, differs significantly from granulation and other areas covered by G-band bright points. We conclude that this peculiar flow pattern is a signature of sunspot decay and the dispersal of magnetic flux.

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Wavelength Dependence of the Helioseismic and Magnetic Imager (HMI) Instrument onboard the Solar Dynamics Observatory (SDO)

Cited by 112 publications

References 10 publications

Artifacts of SDO/HMI data and long-period oscillations of sunspots

Artifacts of SDO/HMI data and long-period oscillations of sunspots

Long quasi-periodic oscillations of sunspots and nearby magnetic structures

Horizontal flow fields observed in Hinode G-band images

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