pb_nov12_icon_movie.gif The November 13, 2012 Total Solar Eclipse:
Predicting the Structure of the Solar Corona
  Using ADAPT Maps
The Sun's magnetic field is a key ingredient to any predictive model of the corona and solar wind.  Full-disk measurements of the (LOS) line-of-sight component of the photospheric magnetic field are the most readily available measurements of the solar magnetic field.  "Synoptic" maps of the photospheric magnetic field are produced by a number of observatories, including the Wilcox Solar Observatory at Stanford University, the National Solar Observatory’s (NSO) SOLIS magnetograph at Kitt Peak, the NSO GONG network, the Solar Tower at Mount Wilson observatory, and the HMI magnetograph aboard NASA’s SDO spacecraft.  The name synoptic is a misnomer; the maps are filled with data over the course of a solar rotation and may contain data that is as much as 27 days old. In actuality, the Sun's magnetic flux is always evolving.  Ideally, a "synchonic" map, which captures the state of the Sun's field at a given time is desired.  Flux evolution models have been successful in reproducing many of the observed properties of photospheric fields, and they can estimate the likely state of the photospheric magnetic field on unobserved portions of the Sun.

The ADAPT flux transport model (Arge et al. 2010), based on the flux evolution model of Worden and Harvey (2000) accounts for the known transport processes in the solar photosphere  (differential rotation, meridional flow, supergranular diffusion, and random flux emergence).  ADAPT improves on the Worden and Harvey model by incorporating rigorous data assimilation methods into it.  SOLIS full-disk magnetograms are assimilated into the model.  The fields within about 25 degrees  of the poles are not assimilated; these fields arise entirely from the long term evolution in the model.   ADAPT is still undergoing testing and our prediction with the ADAPT maps is considered experimental.  Another prediction of the photospheric solar magnetic field using a flux evolution model is being carried out by Karel Schrijver and Marc DeRosa at Lockheed Martin.

The prediction presented on this page used an ADAPT map with data last ingested on November 05.  ADAPT was then run forward in time to predict the photospheric magnetic flux on November 13 at 20:00UT.  We used the same MHD model as for our primary prediction, but the resolution was lower:  a nonuniformly spaced 181 x 161 x 421 (r,theta,phi) grid was used.

The figure on the left shows the predicted polarization brightness (pB) in the solar corona for the eclipse expected on November 13, 2012 at 22:13 UTC (corresponding to the moment of greatest eclipse in the Pacific Ocean).  The state of the solar corona was computed using a 3D magnetohydrodynamic (MHD) simulation.  The pB signal is produced by white light scattered off electrons in the coronal plasma. The image has been radially detrended using the Newkirk vignetting function to account for the fall-off of coronal brightness with distance from the Sun.  Vertical (top) is terrestrial (geocentric) north.  This is the view of the Sun that would be seen by an observer on Earth with a camera aligned so that vertical is toward the Earth’s north pole.  To view this image in a coordinate system aligned with solar north, click here.  Click the image to see it in greater detail.

Predicted polarization brightness (top left) together with traces of the magnetic field lines in the solar corona (top right) for the eclipse expected on November 13, 2012 at 22:13 UTC (with terrestrial north up).  The Sun’s surface shows color contours of the radial component of the photospheric magnetic field as predicted by the ADAPT model. showing the location of active regions (strong magnetic fields).  Click the images for higher resolution pictures.  To view these images in a coordinate system aligned with solar north, click here.

Evolution of the Photospheric Magnetic Field

At this time of the cycle, the Sun is near it's activity maximum, and the Sun's magnetic flux frequently evolves rapidly.  The ADAPT model can account for the surface flows and diffusion of flux, but the emergence of signifcant new active regions can only be accounted for when they are observed on the earthward side of the Sun.  (ADAPT can in principle incorporate new flux estimated from helioseismic far side detections [Arge et al. 2012] but this technique was not employed here.)  Therefore, flux that emerges outside of the earth view will not be accounted for.  This is especially relevant for east limb observations on eclipse day.  Below are shown ADAPT MAPs with data ingested on November 2 and November 5, and the corresponding estimates for the magnetic flux on November 13.  These maps show the radial component of the magnetic field as a function of latitude (vertical axis) and Carrington longitude (horizontal axis). Red shows outward directed magnetic field, and blue shows inward directed field. A smoothed version of the map in the bottom right corner was used for the calculations shown here.  Click on each map to view a larger image.

ADAPT Br Map on 11/02/2012
ADAPT Br Image
11/02/2012 Map Evolved to 11/13/2012
ADAPT Br image
ADAPT Br Map on 11/05/2012
ADAPT Br Image
11/05/2012 Map Evolved to 11/13/2012
ADAPT Br Image

Images of Coronal Emission in EUV and X-Rays

Our 3D MHD model with realistic energy transport allows us to simulate the emission from the corona in extreme ultraviolet and X-ray wavelengths, which can be observed in space by instruments such as STEREO/EUVIHinode/EISHinode/XRT, and the AIA instrument aboard SDO.  To see a comparison of predicted emission for our model and observed EUV emission on November 4, 2012, click here.  To see predicted EUV and X-ray emission on eclipse day, click here.

Movies of Polarization Brightness

We have made movies of the polarization brightness (pB) from our MHD simulation.  This illustrates visually how the solar corona changes as a result of solar rotation. You can see a grayscale movie of pB with a black disk occulting the Sun: a GIF version (4.1 Mbytes, recommended), a QuickTime version (1.8 Mbytes), or a half-resolution GIF version (1.5 Mbytes). You can also see a movie of pB with a blue background and a black disk occulting the Sun: a GIF version (4.1 Mbytes, recommended), or a QuickTime version (3.6 Mbytes).

If your movie player can continuously loop a movie while playing it, set this option to "on" for the best effect. 

ADAPT Related Publications

C. N. Arge, C. J. Henney, J. Koller, C. R. Compeau, S. Young, D. MacKenzie, A. Fay, and J. W. Harvey, "Air Force Data Assimilative Photospheric Flux Transport (ADAPT) Model," Twelfth International Solar Wind Conference, 1216, 343 (2010).

C. N. Arge, C. J. Henney, I. G. Hernandez, W. A. Toussaint, J. Koller, and H. C. Godinez, "Modeling the Corona and Solar Wind using ADAPT Maps that Include Far Side Observations," Thirteenth International Solar Wind Conference, submitted,  (2012).

J. A. Linker,  Z. Mikić, P. Riley, C. Downs, R. Lionello, C. J. Henney, and C. N. Arge, "Coronal and Heliospheric Modeling Using Flux-Evolved Maps," Thirteenth International Solar Wind Conference, submitted,  (2012).

J. Worden and J. Harvey, "An Evolving Synoptic Magnetic Flux map and Implications for the Distribution of Photospheric Magnetic Flux," Sol. Phys., 195, 247 (2000).


Our work is supported by AFOSR, by NASA’s Heliophysics Theory Program (HTP) and NASA’s Living With a Star (LWS) Program, by the Center for Integrated Space Weather Modeling (an NSF Science and Technology Center), and by NSF's Frontiers in Earth System Dynamics Program.  We are grateful to NASA’s Advanced Supercomputing Division (NAS) for an allocation on the Pleiades supercomputer, and the Texas Advanced Computing Center (TACC) for an allocation on the Ranger supercomputer.  Our calculations for the eclipse prediction were performed on these computers.  We thank the Carl Henney and Nick Arge for running the ADAPT model and supplying maps in a timely fashion.

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