Mount Wilson Synoptic Magnetic Fields: Improved Instrumentation, Calibration, and Analysis Applied to the 2000 July 14 Flare and to the Evolution of the Dipole Field

Ulrich, R. K.; Evans, Scott; Boyden, J. E.; Webster, Leslie T.

doi:10.1086/337948

Cited by 91 publications

(67 citation statements)

References 54 publications

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“…The EMD has been applied to the radial, meridional, and east-west components of the magnetic field. We underline that B merid and B EW can provide information on the dynamo-generated poloidal and toroidal components, although they are just a distant reflection and that there is no way to further resolve these two components without a true vector magnetograph (Ulrich et al 2002;Hoeksema & Scherrer 2010). In particular, the EW component (superficial toroidal field) is found to be confined primarily in the range [−35 • , +35 • ] and shows an antisymmetric behavior with respect to the equator, as also happens for the theoretical toroidal field as derived from dynamo models (e.g., Dikpati et al 2004) at the tachocline level (∼0.7 R ).…”

Section: Discussionmentioning

confidence: 97%

“…In order to obtain complete information on the magnetic field vector, synoptic maps of the meridional and east-west components can be derived from B LOS , combined with the differential solar rotation, by applying the method described in Ulrich et al (2002). Briefly, this method works as follows.…”

Section: Data Usedmentioning

confidence: 99%

“…This allows us to identify the set of points having the same position on the solar surface to be combined to form a single synoptic chart point. Then, the magnetic field components B merid and B EW are obtained by weighting the observed B LOS values with both sin(L) and cos(L) (Ulrich et al 2002;Ulrich & Boyden 2005). For each point i on the solar surface, the LOS, the meridional, and the EW components are related as…”

Section: Data Usedmentioning

confidence: 99%

“…Following Ulrich et al (2002), L is taken negative to the west in a way that the field projected in the east-west direction is positive toward the west. Earth's orbit.…”

Section: Data Usedmentioning

confidence: 99%

See 3 more Smart Citations

The Dynamics of the Solar Magnetic Field: Polarity Reversals, Butterfly Diagram, and Quasi-Biennial Oscillations

Vecchio

Laurenza

Meduri

et al. 2012

ApJ

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The spatio-temporal dynamics of the solar magnetic field has been investigated by using NSO/Kitt Peak magnetic synoptic maps covering the period 1976 August-2003 September. The field radial component, for each heliographic latitude, has been decomposed in intrinsic mode functions through the Empirical Mode Decomposition in order to investigate the time evolution of the various characteristic oscillating modes at different latitudes. The same technique has also been applied on synoptic maps of the meridional and east-west components, which were derived from the observed line-of-sight projection of the field by using the differential rotation. Results obtained for the ∼22 yr cycle, related to the polarity inversions of the large-scale dipolar field, show an antisymmetric behavior with respect to the equator in all the field components and a marked poleward flux migration in the radial and meridional components (from about −35 • and +35 • in the southern and northern hemispheres, respectively). The quasi-biennial oscillations (QBOs) are also identified as a fundamental timescale of variability of the magnetic field and associated with poleward magnetic flux migration from low latitudes around the maximum and descending phase of the solar cycle. Moreover, signs of an equatorward drift, at a ∼2 yr rate, seem to appear in the radial and toroidal components. Hence, the QBO patterns suggest a link to a dynamo action. Finally, the high-frequency component of the magnetic field, at timescales less than 1 yr, provides the most energetic contribution and it is associated with the outbreaks of the bipolar regions on the solar surface.

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Section: Discussionmentioning

confidence: 97%

Section: Data Usedmentioning

confidence: 99%

Section: Data Usedmentioning

confidence: 99%

“…Following Ulrich et al (2002), L is taken negative to the west in a way that the field projected in the east-west direction is positive toward the west. Earth's orbit.…”

Section: Data Usedmentioning

confidence: 99%

See 2 more Smart Citations

The Dynamics of the Solar Magnetic Field: Polarity Reversals, Butterfly Diagram, and Quasi-Biennial Oscillations

Vecchio

Laurenza

Meduri

et al. 2012

ApJ

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“…An exception is Ulrich's (2001), which proposes that a hydrodynamic mode of the solar envelope must play an essential role, since the flow is already present at activity minimum, when no active regions are present. The energy in the oscillation is small, however, compared with the inferred magnetic energy of the cycle, hence the suggestion in Ulrich et al (2002) that the oscillation is in step with the cycle because it triggers the eruption of active regions.…”

Section: Introductionmentioning

confidence: 92%

Untitled

2003

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Abstract.A model is presented that explains the 'torsional oscillation' pattern of deviations in the solar rotation rate as a geostrophic flow. The flow is driven by temperature variations near the surface due to the enhanced emission of radiation by the small scale magnetic field. The model explains the sign of the flow, its amplitude and the fact that the maxima occur near the boundaries of the main activity belts. The amplitude of the flow decreases with depth from its maximum at the surface but penetrates over much of the depth of the convection zone, in agreement with the data from helioseismology. It predicts that the flow is axisymmetric only on average, and in reality consists of a superposition of circulations around areas of enhanced magnetic activity. It must be accompanied by a meridional flow component, which declines more rapidly with depth.

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Data‐driven modeling of the solar wind from 1 R_s to 1 AU

Feng

Xiang

2015

JGR Space Physics

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We present here a time‐dependent three‐dimensional magnetohydrodynamic (MHD) solar wind simulation from the solar surface to the Earth's orbit driven by time‐varying line‐of‐sight solar magnetic field data. The simulation is based on the three‐dimensional (3‐D) solar‐interplanetary (SIP) adaptive mesh refinement (AMR) space‐time conservation element and solution element (CESE) MHD (SIP‐AMR‐CESE MHD) model. In this simulation, we first achieve the initial solar wind background with the time‐relaxation method by inputting a potential field obtained from the synoptic photospheric magnetic field and then generate the time‐evolving solar wind by advancing the initial 3‐D solar wind background with continuously varying photospheric magnetic field. The model updates the inner boundary conditions by using the projected normal characteristic method, inputting the high‐cadence photospheric magnetic field data corrected by solar differential rotation, and limiting the mass flux escaping from the solar photosphere. We investigate the solar wind evolution from 1 July to 11 August 2008 with the model driven by the consecutive synoptic maps from the Global Oscillation Network Group. We compare the numerical results with the previous studies on the solar wind, the solar coronal observations from the Extreme ultraviolet Imaging Telescope board on Solar and Heliospheric Observatory, and the measurements from OMNI at 1 astronomical unit (AU). Comparisons show that the present data‐driven MHD model's results have overall good agreement with the large‐scale dynamical coronal and interplanetary structures, including the sizes and distributions of the coronal holes, the positions and shapes of the streamer belts, the heliocentric distances of the Alfvénic surface, and the transitions of the solar wind speeds. However, the model fails to capture the small‐sized equatorial holes, and the modeled solar wind near 1 AU has a somewhat higher density and weaker magnetic field strength than observed. Perhaps better preprocessing of high‐cadence observed photospheric magnetic field (particularly 3‐D global measurements), combined with plasma measurements and higher resolution grids, will enable the data‐driven model to more accurately capture the time‐dependent changes of the ambient solar wind for further improvements. In addition, other measures may also be needed when the model is employed in the period of high solar activity.

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Mount Wilson Synoptic Magnetic Fields: Improved Instrumentation, Calibration, and Analysis Applied to the 2000 July 14 Flare and to the Evolution of the Dipole Field

Cited by 91 publications

References 54 publications

The Dynamics of the Solar Magnetic Field: Polarity Reversals, Butterfly Diagram, and Quasi-Biennial Oscillations

The Dynamics of the Solar Magnetic Field: Polarity Reversals, Butterfly Diagram, and Quasi-Biennial Oscillations

Untitled

Data‐driven modeling of the solar wind from 1 R_s to 1 AU

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Mount Wilson Synoptic Magnetic Fields: Improved Instrumentation, Calibration, and Analysis Applied to the 2000 July 14 Flare and to the Evolution of the Dipole Field

Cited by 91 publications

References 54 publications

The Dynamics of the Solar Magnetic Field: Polarity Reversals, Butterfly Diagram, and Quasi-Biennial Oscillations

The Dynamics of the Solar Magnetic Field: Polarity Reversals, Butterfly Diagram, and Quasi-Biennial Oscillations

Untitled

Data‐driven modeling of the solar wind from 1 Rs to 1 AU

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Product

Resources

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Data‐driven modeling of the solar wind from 1 R_s to 1 AU