The Solar Oscillations Investigation - Michelson Doppler Imager

Scherrer, P. H.; Bogart, R. S.; Bush, R. I.; Hoeksema, J. T.; Kosovichev, A. G.; Schou, J.; Rosenberg, W. J.; Springer, Larry; Tarbell, T. D.; Title, A. M.; Wolfson, C. J.; Zayer, I.

doi:10.1007/bf00733429

Cited by 2,300 publications

(1,394 citation statements)

References 23 publications

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“…Five instruments were involved in co-spatial observations on September 26, 2008: MDI (Scherrer et al 1995) on SoHO, the X-Ray Telescope (XRT, Golub et al 2007), the broad-band filter imager (BFI) and the narrow-band filter imager (NFI) of the solar optical telescope (SOT, Tsuneta et al 2008) onboard Hinode. Each of them provided an 8 hr time series of data, from 15:00 UT to 23:00 UT.…”

Section: Observationsmentioning

confidence: 99%

Relationship between supergranulation flows, magnetic cancellation and network flares

Attié

Innes

Solanki

et al. 2016

A&A

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Context. Photospheric flows create a network of often mixed-polarity magnetic field in the quiet Sun, where small-scale eruptions and network flares are commonly seen. Aims. The aim of this paper is (1) to describe the characteristics of the flows that lead to these energy releases, (2) to quantify the energy build up due to photospheric flows acting on the magnetic field, and (3) to assess its contribution to the energy of small-scale, short-lived X-ray flares in the quiet Sun. Methods. We used photospheric and X-ray data from the SoHO and Hinode spacecraft combined with tracking algorithms to analyse the evolution of five network flares. The energy of the X-ray emitting thermal plasma is compared with an estimate of the energy built up due to converging and sheared flux. Results. Quiet-Sun network flares occur above sites of converging opposite-polarity magnetic flux that are often found on the outskirts of network cell junctions, sometimes with observable vortex-like motion. In all studied flares the thermal energy was more than an order of magnitude higher than the magnetic free energy of the converging flux model. The energy in the sheared field was always higher than in the converging flux but still lower than the thermal energy. Conclusions. X-ray network flares occur at sites of magnetic energy dissipation. The energy is probably built up by supergranular flows causing systematic shearing of the magnetic field. This process appears more efficient near the junction of the network lanes. Since this work relies on 11 case studies, our results call for a follow-up statistical analysis to test our hypothesis throughout the quiet Sun.

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Section: Observationsmentioning

confidence: 99%

Relationship between supergranulation flows, magnetic cancellation and network flares

Attié

Innes

Solanki

et al. 2016

A&A

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“…We computed the FTEs and predicted the SWS for solar cycles23 and early24 (two years), i.e., from 1996 to 2010 (CRs: 1912-2104), using the SOHO/MDI synoptic maps (Scherrer et al 1995) as input to the models. These synoptic maps have their polar fields filled by interpolation (Sun et al 2011 In order to obtain the functional relationship between FTE and SWS, we need solar wind data at 1 au.…”

Section: Models and Datamentioning

confidence: 99%

Controlling Influence of Magnetic Field on Solar Wind Outflow: An Investigation Using Current Sheet Source Surface Model

Poduval

2016

ApJL

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This Letter presents the results of an investigation into the controlling influence of large-scale magnetic field of the Sun in determining the solar wind outflow using two magnetostatic coronal models: current sheet source surface (CSSS) and potential field source surface. For this, we made use of the Wang and Sheeley inverse correlation between magnetic flux expansion rate (FTE) and observed solar wind speed (SWS) at 1 au. During the period of study, extended over solar cycle23 and beginning of solar cycle24, we found that the coefficients of the fitted quadratic equation representing the FTE-SWS inverse relation exhibited significant temporal variation, implying the changing pattern of the influence of FTE on SWS over time. A particularly noteworthy feature is an anomaly in the behavior of the fitted coefficients during the extended minimum, 2008-2010 (CRs 2073 -2092, which is considered due to the particularly complex nature of the solar magnetic field during this period. However, this variation was significant only for the CSSS model, though not a systematic dependence on the phase of the solar cycle. Further, we noticed that the CSSS model demonstrated better solar wind prediction during the period of study, which we attribute to the treatment of volume and sheet currents throughout the corona and the more accurate tracing of footpoint locations resulting from the geometry of the model.

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“…magnetogram from SOHO/MDI (Scherrer et al 1995) in a wide region around the area of interest. The MDI signal in the quietest areas of our FOV is (1.…”

Section: Observations and Data Processingmentioning

confidence: 99%

Phase diversity restoration of sunspot images

Bonet¹,

Márquez

Müller

et al. 2005

A&A

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Abstract. Two time series, taken simultaneously in the G-band and in white-light, and corrected for telescope aberrations and turbulence perturbations using the method of phase diversity, are employed to study the motions of granules and G-band bright points (GBPs) in the moat of an old regular sunspot. Local correlation tracking and feature tracking have been utilized for this purpose. A large-scale radial outflow with a mean velocity of 0.51 km s −1 has been measured in the sunspot moat. Centres of diverging horizontal motions, identified with families of granules formed by repeatedly splitting granules, move away from the sunspot. Most of the GBPs in the moat also move outwards through radially orientated "channels" (confined between the borders of adjacent families) with velocities comparable to those of the adjacent granules. However, 6% of the GBPs move faster (>1.4 km s −1 ) than the neighbouring granules. GBPs in the moat are not regularly distributed but they are less frequent on its solar centre side.

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The Solar Oscillations Investigation - Michelson Doppler Imager

Cited by 2,300 publications

References 23 publications

Relationship between supergranulation flows, magnetic cancellation and network flares

Relationship between supergranulation flows, magnetic cancellation and network flares

Controlling Influence of Magnetic Field on Solar Wind Outflow: An Investigation Using Current Sheet Source Surface Model

Phase diversity restoration of sunspot images

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