A. A. Norton

article

Observables Processing for the Helioseismic and Magnetic Imager Instrument on the Solar Dynamics Observatory

S. Couvidat, J. Schou, J. T. Hoeksema, R. S. Bogart, more

Solar Physics > 2016 > 291 > 7 > 1887-1938

NASA’s Solar Dynamics Observatory (SDO) spacecraft was launched 11 February 2010 with three instruments onboard, including the Helioseismic and Magnetic Imager (HMI). After commissioning, HMI began normal operations on 1 May 2010 and has subsequently observed the Sun’s entire visible disk almost continuously. HMI collects sequences of polarized filtergrams taken at a fixed cadence with two 4096...

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The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Magnetohydrodynamics Simulation Module for the Global Solar Corona

K. Hayashi, J. T. Hoeksema, Y. Liu, M. G. Bobra, more

Solar Physics > 2015 > 290 > 5 > 1507-1529

Time-dependent three-dimensional magnetohydrodynamics (MHD) simulation modules are implemented at the Joint Science Operation Center (JSOC) of the Solar Dynamics Observatory (SDO). The modules regularly produce three-dimensional data of the time-relaxed minimum-energy state of the solar corona using global solar-surface magnetic-field maps created from Helioseismic and Magnetic Imager (HMI) full-disk...

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Hemispheric Coupling: Comparing Dynamo Simulations and Observations

A. A. Norton, P. Charbonneau, D. Passos

Space Science Reviews > 2014 > 186 > 1-4 > 251-283

Numerical simulations that reproduce solar-like magnetic cycles can be used to generate long-term statistics. The variations in north-south hemispheric solar cycle synchronicity and amplitude produced in simulations has not been widely compared to observations. The observed limits on solar cycle amplitude and phase asymmetry show that hemispheric sunspot area production is no more than 20 % asymmetric...

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The Sun’s Interior Structure and Dynamics, and the Solar Cycle

A.-M. Broomhall, P. Chatterjee, R. Howe, A. A. Norton, more

Space Science Reviews > 2014 > 186 > 1-4 > 191-225

The Sun’s internal structure and dynamics can be studied with helioseismology, which uses the Sun’s natural acoustic oscillations to build up a profile of the solar interior. We discuss how solar acoustic oscillations are affected by the Sun’s magnetic field. Careful observations of these effects can be inverted to determine the variations in the structure and dynamics of the Sun’s interior as the...

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Recovering Joy’s Law as a Function of Solar Cycle, Hemisphere, and Longitude

B. H. McClintock, A. A. Norton

Solar Physics > 2013 > 287 > 1-2 > 215-227

Bipolar active regions in both hemispheres tend to be tilted with respect to the East–West Equator of the Sun in accordance with Joy’s law, which describes the average tilt angle as a function of latitude. Mt. Wilson Observatory data from 1917 – 1985 are used to analyze the active-region tilt angle as a function of solar cycle, hemisphere, and longitude, in addition to the more common dependence on...

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Polarization Calibration of the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO)

J. Schou, J. M. Borrero, A. A. Norton, S. Tomczyk, more

Solar Physics > 2012 > 275 > 1-2 > 327-355

As part of the overall ground-based calibration of the Helioseismic and Magnetic Imager (HMI) instrument an extensive set of polarimetric calibrations were performed. This paper describes the polarimetric design of the instrument, the test setup, the polarimetric model, the tests performed, and some results. It is demonstrated that HMI achieves an accuracy of 1% or better on the crosstalks between...

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Design and Ground Calibration of the Helioseismic and Magnetic Imager (HMI) Instrument on the Solar Dynamics Observatory (SDO)

J. Schou, P. H. Scherrer, R. I. Bush, R. Wachter, more

Solar Physics > 2012 > 275 > 1-2 > 229-259

The Helioseismic and Magnetic Imager (HMI) investigation (Solar Phys. doi: 10.1007/s11207-011-9834-2 , 2011) will study the solar interior using helioseismic techniques as well as the magnetic field near the solar surface. The HMI instrument is part of the Solar Dynamics Observatory (SDO) that was launched on 11 February 2010. The instrument is designed to measure the Doppler shift, intensity, and...

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Solar-Cycle Characteristics Examined in Separate Hemispheres: Phase, Gnevyshev Gap, and Length of Minimum

A. A. Norton, J. C. Gallagher

Solar Physics > 2010 > 261 > 1 > 193-207

According to research results from solar-dynamo models, the northern and southern hemispheres may evolve separately throughout the solar cycle. The observed phase lag between the northern and southern hemispheres provides information regarding how strongly the hemispheres are coupled. Using hemispheric sunspot-area and sunspot-number data from Cycles 12 – 23, we determine how out of phase the separate...

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A Note on Saturation Seen in the MDI/SOHO Magnetograms

Y. Liu, A. A. Norton, P. H. Scherrer

Solar Physics > 2007 > 241 > 1 > 185-193

A type of saturation is sometimes seen in sunspot umbrae in MDI/SOHO magnetograms. In this paper, we present the underlying cause of such saturation. By using a set of MDI circular polarization filtergrams taken during an MDI line profile campaign observation, we derive the MDI magnetograms using two different approaches: the on-board data processing and the ground data processing, respectively. The...

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Spectral Line Selection for HMI: A Comparison of Fe I 6173 Å and Ni I 6768 Å

A. A. Norton, J. Pietarila Graham, R. K. Ulrich, J. Schou, more

Solar Physics > 2006 > 239 > 1-2 > 69-91

We present a study of two spectral lines, Fe I 6173 Å and Ni I 6768 Å, that were candidates to be used in the Helioseismic and Magnetic Imager (HMI) for observing Doppler velocity and the vector magnetic field. The line profiles were studied using the Mt. Wilson Observatory, the Advanced Stokes Polarimeter and the Kitt Peak-McMath Pierce telescope and one-meter Fourier transform spectrometer atlas...

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Search results for: A. A. Norton

Observables Processing for the Helioseismic and Magnetic Imager Instrument on the Solar Dynamics Observatory

The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Magnetohydrodynamics Simulation Module for the Global Solar Corona

Hemispheric Coupling: Comparing Dynamo Simulations and Observations

The Sun’s Interior Structure and Dynamics, and the Solar Cycle

Recovering Joy’s Law as a Function of Solar Cycle, Hemisphere, and Longitude

Polarization Calibration of the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO)

Design and Ground Calibration of the Helioseismic and Magnetic Imager (HMI) Instrument on the Solar Dynamics Observatory (SDO)

Solar-Cycle Characteristics Examined in Separate Hemispheres: Phase, Gnevyshev Gap, and Length of Minimum

A Note on Saturation Seen in the MDI/SOHO Magnetograms

Spectral Line Selection for HMI: A Comparison of Fe I 6173 Å and Ni I 6768 Å

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