The July 11, 2010 Total Solar Eclipse

On Sunday, July 11, 2010, a total eclipse of the Sun was visible in the southern hemisphere. The total eclipse followed a path through the South Pacific Ocean crossing only the Cook Islands and Easter Island. A partial eclipse was visible over a much larger path, including the southern portion of South America. The eclipse began at 18:15 UT, when the Moon’s shadow first touched the Earth. The track was 179 km wide, and totality lasted initially for 2 min 42 sec along the central line. By the time it reached the Cook Islands, totality lasted for 3 min 18 sec. Easter Island enjoyed 4 min 41 sec of totality. Totality finally ended 2 hours and 39 minutes later as the shadow crossed the Andes, into Argentina. For a detailed description of the eclipse path, see NASA’s Eclipse page; for useful information about eclipse photography, see Fred Espenak’s Eclipse web site. Detailed information concerning all eclipses occurring in 2010 can be found in this PDF document.

On July 2, 2010, we started an MHD computation of the solar corona, in preparation for our prediction of what the solar corona would look like during this eclipse. We used photospheric magnetic field data for Carrington rotation 2097, measured up to June 16, 2010, using the MDI magnetograph aboard the SOHO spacecraft. We typically also use magnetic field measurements from the Wilcox Solar Observatory at Stanford University and the National Solar Observatory SOLIS vector magnetograph at Kitt Peak.

A preliminary prediction of the state of the solar corona during the eclipse based on this data was posted on this web site on July 5, 2010. (This prediction was updated slightly on July 6 to correct an error in the solar viewing parameters for the moment of greatest eclipse.) This preliminary prediction can be found here. On July 6, 2010 we started a new calculation with updated magnetic field data that was measured with MDI up to July 3, 2010. This page has the updated (and final) prediction, which was posted on July 8, 2010.

Our prediction is based on a magnetohydrodynamic model of the solar corona with improved energy transport. We used this model for the first time to predict the structure of the corona prior to the March 29, 2006 total solar eclipse. Since then, we have predicted a number of other total eclipses. The improved energy equation model includes the effects of coronal heating, the conduction of heat parallel to the magnetic field lines, radiative losses, and the effect of Alfvén waves. This produces a significantly better estimate of the plasma temperature and density in the corona. For technical details about our improved model, please see the publications below.

If you are curious, you can see the milestones in achieving our prediction.

Predicted polarization brightness, terrestrial north up — Predicted polarization brightness (pB) in the solar corona for the eclipse expected on July 11, 2010 at 19:33 UT (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. Views aligned with solar north are on the original solar-north page.

Predicted polarization brightness with photospheric field contours — Predicted polarization brightness (left) together with traces of the magnetic field lines in the solar corona (right) for the eclipse expected on July 11, 2010 at 19:33 UT (with terrestrial north up). The Sun’s surface shows color contours of the radial component of the measured photospheric magnetic field from the MDI magnetograph, showing the location of active regions (strong magnetic fields).

Traces of the magnetic field lines with photospheric field contours — Predicted polarization brightness (left) together with traces of the magnetic field lines in the solar corona (right) for the eclipse expected on July 11, 2010 at 19:33 UT (with terrestrial north up). The Sun’s surface shows color contours of the radial component of the measured photospheric magnetic field from the MDI magnetograph, showing the location of active regions (strong magnetic fields).

Evolution of the Photospheric Magnetic Field

The photospheric magnetic field maps we use for our calculations are built up from daily observations of the Sun during a solar rotation. These maps give a good approximation of the Sun’s magnetic flux if the large-scale flux does not change much throughout a rotation. Previously, we have computed coronal models for an eclipse during the declining phase of the last solar cycle (November 3, 1994), for eclipses during solar minimum (October 24, 1995, March 9, 1997, March 29, 2006, August 1, 2008, and July 22, 2009), one eclipse during the early rising phase of solar cycle 23 (February 26, 1998), one eclipse approaching solar maximum (August 11, 1999), and two eclipses near solar maximum (June 21, 2001 and December 4, 2002).

The July 11, 2010 eclipse occurred during the rising phase of solar cycle 24, so the solar corona had a more complex structure than at solar minimum.

These figures show the evolution of the radial component (Br) of the solar photospheric magnetic field for three Carrington rotations preceding the eclipse, as measured by the MDI magnetograph aboard the SOHO spacecraft. We use smoothed versions of these magnetic field maps in our calculations. We used the data for Carrington rotation (CR) 2097 in our calculation for our preliminary eclipse prediction, which was posted on our web site on July 5, 2010. The last panel shows the magnetic field data that was used for the final eclipse prediction, which is shown on this page.

Photospheric magnetic field map for CR2096 — These maps show the radial component of the magnetic field deduced from the measured photospheric 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. The dark regions near the top and bottom indicate areas near the solar poles where it is not possible to estimate the radial component of the magnetic field due to projection effects.

Photospheric magnetic field map for CR2097 — These maps show the radial component of the magnetic field deduced from the measured photospheric 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. The dark regions near the top and bottom indicate areas near the solar poles where it is not possible to estimate the radial component of the magnetic field due to projection effects.

Images and Movies of Coronal Emission in EUV and X-Rays

Our 3D MHD model with improved energy transport allows us to simulate the emission from the corona in extreme ultraviolet and X-ray wavelengths. The Sun can be observed in these wavelengths from space. In particular, the SOHO/EIT, TRACE, STEREO/EUVI, and Hinode/EIS telescopes routinely take EUV images of the solar corona, and the Yohkoh/SXT (no longer operating) and Hinode/XRT telescopes image the soft X-ray Sun. Our simulated coronal emission is available on the original emission page.

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. The left movie shows pB in grayscale with a black disk occulting the Sun; the right shows pB with a blue background.

Polarization Brightness(grayscale)

Polarization Brightness(blue background)

Movies of Magnetic Field Lines

We have made movies of magnetic field lines and simulated emission from the Hinode XRT (Al mesh filter) and the SOHO EIT (195 Å) instruments. These are simulated “synoptic” emission images wrapped on the sphere, so emission on the limbs is not visible. Blue field lines are closed in both sets of movies. Green field lines are open for the XRT images, red field lines are open for the EIT images. The movies illustrate the relationship of closed and open structures to features in emission.

Field Lines and Hinode XRT Emission

Field Lines and EIT 195 Å Emission

Publications

For technical details about our model, please see the following publications:

Z. Mikić, J. A. Linker, D. D. Schnack, R. Lionello, and A. Tarditi, “Magnetohydrodynamic Modeling of the Global Solar Corona,” Physics of Plasmas, 6, 2217 (1999).
Z. Mikić, J. A. Linker, P. Riley, and R. Lionello, “Predicting the Structure of the Solar Corona During the 11 August 1999 Total Solar Eclipse,” in The Last Total Solar Eclipse of the Millennium (W. Livingston and A. Ozguc, eds.), ASP Conference Series, Vol. 205, p. 162 (2000). Download PDF
Z. Mikić, J. A. Linker, R. Lionello, P. Riley, and V. Titov, “Predicting the Structure of the Solar Corona for the Total Solar Eclipse of March 29, 2006,” in Solar and Stellar Physics Through Eclipses (O. Demircan, S. O. Selam, and B. Albayrak, eds.), ASP Conference Series, Vol. 370, p. 299 (2007). Download PDF
R. Lionello, J. A. Linker, and Z. Mikić, “Multispectral Emission of the Sun During the First Whole Sun Month: Magnetohydrodynamic Simulations,” Astrophys. J., 690, 902 (2009). Access Article
V. Rušin, M. Druckmüller, P. Aniol, M. Minarovjech, M. Saniga, Z. Mikić, J. A. Linker, R. Lionello, P. Riley, and V. S. Titov, “Comparing Eclipse Observations of the 2008 August 1 Solar Corona with an MHD Model Prediction,” Astron. Astrophys., 513, A45 (2010). Access Article

Acknowledgments

Our work is supported by NASA, AFOSR, and NSF through the Strategic Capabilities program, by NASA’s Heliophysics Theory Program (HTP), by the Center for Integrated Space Weather Modeling (an NSF Science & Technology Center), by NASA’s Supporting Research & Technology (SR&T) Program, and by NASA’s Living With a Star (LWS) Program. We thank the staff at the Texas Advanced Computing Center (TACC) for graciously providing us with dedicated time on their massively parallel supercomputer Ranger, and NASA’s Advanced Supercomputing Division (NAS) for an allocation on the Pleiades supercomputer. Our calculations for the eclipse prediction were performed on these computers. We thank Yang Liu, Todd Hoeksema, and Jeneen Sommers of the Solar Physics Group at Stanford University for providing us with timely access to MDI magnetograph data and for sharing the latest calibrated data with us.

Archived prediction, converted from the original 2010 page. Movies originally offered as GIF/QuickTime downloads are embedded above.