HAO 2011 Profiles In Science: Dr. Rebecca Centeno

 

Contact
303-497-1581
rce@ucar.edu

Area of expertise: Magnetic properties of the solar atmosphere

Specialties: Spectropolarimetry; theoretical radiative transfer; chromospheric magnetism and wave propagation

Profile:

Rebeca Centeno has a background in spectropolarimetry as a tool to infer the magnetic properties of the solar atmosphere. She is currently working for the Helioseismic and Magnetic Imager (HMI) investigation on the NASA Solar Dynamics Observatory (SDO) mission. Other interests include: theoretical radiative transfer, chromospheric magnetism and wave propagation in the solar atmosphere.

SDO/HMI produces data that help determine what the sources and mechanisms of variability in the Sun's interior are. The instrument measures the Doppler shift and the polarization of the Fe I 6173 Å line, on the entire solar disk at a relatively-high cadence, in order to study the oscillations and the evolution of the full vector magnetic field of the solar Photosphere. After the data are properly calibrated, they are passed to a Milne-Eddington inversion code whose purpose is to infer certain aspects of the physical conditions in the Sun's Photosphere, such as the full 3-D topology of the magnetic field and the line-of-sight velocity at the solar surface. Despite the trade-offs that an ambitious project that wants to measure "all the Sun, all the time" has to make (i.e. limited spectral resolution and polarimetric sensitivity), HMI data produce results that are quantitatively comparable to those of state-of-the art, high resolution instruments, like the Spectro-Polarimeter on board Hinode.

Publications:

(1) HMI: First Results:
Centeno, R.; Tomczyk, S.; Borrero, J. M.; Couvidat, S. Hayashi, K.; Hoeksema, T.; Liu, Y.; Schou, J. 2011: In Solar Polarization 6. Proceedings of a conference held in Maui, Hawaii, USA on May 30 to June 4, 2010. Edited by J. R. Kuhn, D. M. Harrington, H. Lin, S. V. Berdyugina, J. Trujillo-Bueno, S. L. Keil, and T. Rimmele. San Francisco: Astronomical Society of the Pacific, p.147.

Abstract: The Helioseismic and Magnetic Imager (HMI) has just started producing data that will help determine what the sources and mechanisms of variability in the Sun's interior are. The instrument measures the Doppler shift and the polarization of the Fe I 6173 Å line, on the entire solar disk at a relatively-high cadence, in order to study the oscillations and the evolution of the full vector magnetic field of the solar Photosphere. After the data are properly calibrated, they are given to a Milne-Eddington inversion code (VFISV, Borrero et al. 2010) whose purpose is to infer certain aspects of the physical conditions in the Sun's Photosphere, such as the full 3-D topology of the magnetic field and the line-of-sight velocity at the solar surface. We will briefly describe the characteristics of the inversion code, its advantages and limitations -both in the context of the model atmosphere and the actual nature of the data-, and other aspects of its performance on such a remarkable data load. Also, a cross-comparison with near-simultaneous maps from the Spectro-Polarimeter (SP) onboard Hinode will be made.

(2) Continuous Upflow of Material in an Active Region Filament from the Photosphere to the Corona:
Kuckein, C.; Centeno, R.; Martínez Pillet, V. 2011: In Solar Polarization 6. Proceedings of a conference held in Maui, Hawaii, USA on May 30 to June 4, 2010. Edited by J. R. Kuhn, D. M. Harrington, H. Lin, S. V. Berdyugina, J. Trujillo-Bueno, S. L. Keil, and T. Rimmele. San Francisco: Astronomical Society of the Pacific, p.275.

Abstract: Using spectropolarimetric data of an Active Region (AR) filament we have carried out inversions in order to infer vector magnetic fields in the photosphere (Si I line) and in the chromosphere (He I line). Our filament lies above the polarity inversion line (PIL) situated close to disk center and presents strong Zeeman-like signatures in both photospheric and chromospheric lines. Pore-like formations with both polarities are identified in the continuum under the PIL. The azimuth ambiguity is solved at both heights using the AZAM code. A comparison between the photospheric and chromospheric vector magnetic fields revealed that they are well aligned in some areas of the filament. However, especially at chromospheric heights, the magnetic field is mostly aligned with the dark threads of the filament. Velocity signatures indicating upflows of field lines are found at both heights. The combination of all these findings strongly suggests an emerging flux rope scenario.