UPDATE TIME: 03/07/2019


Credit: Adrien Mauduit.

Figure 1. Preliminary observational results.

Figure 2. Predicted magnetic field overlaid on observations.

Various observational facilities recorded the view of the beautiful diamond ring structure during the Total solar eclipse of 2019 July 2 in South America. While we wait for the processed white-light images to be available, here are some premilinary observational results. Fig. 1 (left) is the white light corona observed by the MLSO K-cor instrument. Fig. 1 (right) is our predicted coronal structure. The two predicted streamers on the East and West Limb of the Sun were observed on the day of the eclipse.

UPDATE TIME: 21/06/2019

Figure 1. Prediction of the Sun's coronal magnetic field structure.

We predict two large-scale petal-like structures (known as helmet streamers) on each limb (side) of the Sun on the day of the eclipse. These petal-like streamers consist of closed magnetic loops that connect opposite magnetic polarities on the Sun's surface. Both the streamer structures would be cross-equatorial. The streamer on the right (west) limb of the Sun would be centered just north of the equator, and the streamer on the left (east) limb would be centered just south of the equator. The northern edge of the streamer on the left limb would be smoothed out by emission from closed magnetic field lines that lie adjacent to this edge. Open magnetic fields dominate the Sun's north and south pole which is expected at this time nearing the minimum activity level between two solar maxima. A plausible peudo-streamer like elongated structure exists in the north-east limb at high latitudes but close scrutiny shows that the relative configuration of the loops are unlikely to lead to a visible pseudo-streamer on the day of the eclipse (but may later mature in to one over solar rotational timescales well after the eclipse if favourable conditions arise). In large-angle coronagraph images acquired during the eclipse bright extended plumes (beyond the source surface) are expected to be aligned with the line joining the tips of closed magnetic field lines to the cusps of the predicted streamers.

Figure 2. Prediction of Sun's synthetic "white-light" coronal structure.

The predicted white light corona depicts what is expected to be seen during the totality phase of the eclipse in long- or multiple-exposure photographic images such as those acquired by expert eclipse photographers (see, e.g., http://www.zam.fme.vutbr.cz/~druck/) or by the MLSO-K coronagraph.

Figure 3. A movie of the predicted 3D solar coronal magnetic field structure as the viewpoint is rotated in the direction of rotation of the Sun. The 3D eclipse view is indicated with the date 2 July 2019. Note the presence of closed magnetic field lines near limb which connect opposite polarity patches on the solar disk facing Earth to the far side of the Sun (on the day of the eclipse). The presence of these structures become apparent in this rendering.


Figure 4. Plane of sky magnetic field vectors (red arrows) and linear polarization vectors (blue lines).
Figure 5. Degree of linear polarization, L/I.
Figure 6. The circular polarization (Stokes V/I).


The upcoming solar eclipse on 2 July 2019 will occur just 2.4 days after Moon's perigee, meaning the total duration of totality will be relatively long. The length of this eclipse will be 4 minutes 33 seconds. The maximum coverage during the eclipse will occur at 19:24:08 UTC in the South Pacific about 1080 kilometers north of Easter Island. It will be visible during sunset from a thin swath that passes the South Pacific Ocean and South America across the Andes, including parts of Chile and Argentina.

Path of totality (colored red) during the total solar eclipse of 2019 July 2 is shown where the black dot cporresponds to Moon's Shadow and the concentric patches are the penumbra. Credits: NASA GSFC.


Novel utilization of two disparate computational models based on a theoretical framework postulated in Nandy et al. (2018) allows long-term prediction of the Sun's coronal magnetic field structure. The Predictive Solar Surface Flux Transport (PSSFT) model developed at CESSI (Bhowmik & Nandy 2018) is forward run for 51 days (since the last observed active region emergence) to first predict the surface magnetic field distribution on the Sun's surface expected on 2 July 2019. Subsequently a potential field source surface model utilizes the predicted solar surface field as its boundary condition to extrapolate the coronal fields expected on the day of the eclipse.

The synthetic white light corona is generated from the predicted coronal fields by assigning more weight to closed field lines relative to the open field lines, and utilizing an inverse r2 filter to capture the density stratification of the magnetic loops expected in the corona.

Possibility of pseudo-streamers (visibly bright elongated collimated radial structures overlying double arcade loop-like structures) is evaluated based on examination of the underlying magnetic topology on the surface and low-lying arcade loops.

The forward modeling of the expected coronal polarization characteristics is performed utilizing the FORWARD model.


The prediction team was led by Dibyendu Nandi, Professor at the Department of Physical Sciences and the Center of Excellence in Space Sciences India at IISER Kolkata. The full team consists of:

*Dibyendu Nandi is an Associate of the Inter-University Centre for Astronomy and Astrophysics (Pune).



This eclipse prediction for 2 July 2019 has been conducted at CESSI – a multi-institutional Center of Excellence established at IISER Kolkata and funded by the Ministry of Human Resource Development, Government of India. We acknowledge funding from the DST-INSPIRE program. We acknowledge utilization of data from NASA's Solar Dynamics Observatory Helioseismic and Magnetic Imager (HMI) instrument maintained at Stanford University and the Royal Greenwich Observatory/United States Air Force-NOAA active region database compiled by David H. Hathaway. We acknowledge utilization of an open-source PFSS Extrapolation code developed by Anthony R. Yeates (Durham University, UK). We are grateful to Prosenjit Lahiri and the CESSI team for helping with content and the design of this website.


Dibyendu Nandi: dnandi @ iiserkol . ac . in


The solar corona is very faint compared to the bright solar surface. Thus it is extremely hard to observe the corona unless any object occults the bright solar disk. This occulting object can be the Moon while passing in front of the Sun or an artificial disk mounted on a satellite (a coronagraph). Currently, European Space Agency's Solar and Heliospehric Observatory has an instrument called LASCO which is a space-based coronagraph. India plans to launch the Aditya-L1 satellite which will also carry a coronagraph for observing the Sun's coronal structure. The Daniel K. Inouye Solar Telescope ( DIKIST ) and the Coronal Multichannel Polarimeter ( CoMP ) instruments are also expected to commission ground-based coronagraphs in the near future.

Apart from such instruments, solar eclipses during occultation by the Moon provide excellent opportunities to study the Sun's corona. But why do we need to study the corona at all and why do space agencies and countries make so much effort to deploy Sun observing instruments in space and on the ground?

The reason is that coronal magnetic field dynamics lead to solar flares, solar storms, and Coronal Mass Ejections (CMEs). The effect of the eruption of plasma and charged ions from the Sun during these events can be felt in the entire solar system. These events affect the Earth's outer atmosphere and our technologies leading to power outages and disruption of communication and GPS networks. They can also damage satellites and more importantly harm our astronauts orbiting around the Earth jeopardizing their health through doses of high radiation and energetic particles. As we get more and more dependent on space-reliant technologies with every passing day, it becomes imperative for us to study these solar phenomena and develop the understanding to be able to predict these events with a reasonable degree of accuracy.

Most of these eruptive events are associated with the magnetic field distribution of the corona. However, due to the scarcity of observation of the coronal magnetic field, scientists rely on computational models to constrain the magnetic nature of the corona. These scientific models, with an in-depth theoretical understanding of the dynamics of the solar corona can also provide a meaningful prediction of coronal magnetic field structures. Thus, observing the corona during an eclipse gives us an excellent opportunity to test the correctness of our models, and refine them leading to improved forecasting capabilities. The primary objective of CESSI is to develop advanced computational models for understanding solar activity and enabling space weather forecasting.


A solar eclipse occurs when the Moon is between the Sun and the Earth, so that the visible disk of the Sun, which is the photosphere, is 'occulted' or covered by the Moon. As is obvious, eclipses provide an excellent opportunity to study the Sun's 'crown'- its corona (otherwise invisible due to the blindingly bright photosphere), which has kept astrophysicists puzzled with its million-degree temperature since a long, long time! As the Moon comes between the Sun and the Earth only on a new moon day, a solar eclipse can only occur on a new moon day. The reason why a solar eclipse doesn't occur on every new moon day is that the orbit of the Moon is 5 degrees inclined to the ecliptic, which is the plane in which the Earth revolves around the Sun. Thus, at the least two and at the most five solar eclipses only can occur in a year. Solar eclipses can be observed from only a narrow strip on the Earth which falls in the shadow of the Moon, unlike lunar eclipses which can be observed from the entire hemisphere having night. Also, a total lunar eclipse can last up to 2 hours while the upper limit for any solar eclipse's totality is 8 minutes. This is because the Moon's shadow on the Earth is small. In fact, at least 92% of the sunlight usually received still reaches the Earth even during a solar eclipse. Seen from the Moon, the Earth would still look bright during a solar eclipse with only a small patch darkened by the shadow of the Moon. Solar eclipses can be total, partial, or annular. In a total solar eclipse, the entire visible disk of the Sun is occulted, turning day into night for a few minutes. Only the partial disc of the Sun appears to be 'eaten' by the Moon in a partial eclipse as the name suggests. Annular solar eclipse, on the other hand, is one in which the Moon is too far away to cover the entire disc of the Sun, and so a thin ring of the photosphere is visible in this one. It's obvious that an annular eclipse occurs when the apparent size of the Sun is larger than the Moon, whereas the total one occurs when the apparent size of the Moon is bigger than the Sun.

The predictive capability of the procedure employed by CESSI for the upcoming eclipse was also tested during 2017 August 21 Great American Solar eclipse. The predicted coronal magnetic field distribution along with the location and structure of the helmet streamers and pseudo-streamer had a remarkable resemblance with the observed white light image of the corona taken on the day of the eclipse.

People who chase eclipses around the globe and study them using astronomical tools are called 'umbraphiles'!


Eclipses have fascinated human civilizations since ancient times. Naturally, lunar and solar eclipses have spawned various myths and superstitions among the general populace since ages. To read more click here ( link).


One of the most historic solar eclipses was the total solar eclipse of 1919 May 29. By measuring the distance to background stars with and without the Sun, the gravitational lensing effect of the Sun as predicted by Einstein's General Theory of Relativity was confirmed by Arthur Eddington by taking down observations during this eclipse. Only a solar eclipse can facilitate the observation of stars with the Sun, making this eclipse a historic one! The last solar eclipse occurred on 2019 January 6. It was a partial solar eclipse which was visible from Asia and Alaska. Only total solar eclipses provide a natural condition suitable for coronal studies. The last total solar eclipse was "The Great American Eclipse" of 2017 August 21, which was also predicted by CESSI to a high degree of accuracy. Here is a list of eclipses for the year 2019.


  1. ISRO's Aditya L1 Mission
  2. Coronal Multi-channel Polarimeter (CoMP)
  3. Daniel K. Inouye Solar Telescope (DKIST)
  4. Website: The Great American Solar Eclipse
  5. Website: http://eclipsewise.com/oh/ec2019.html
  6. Website: https://en.wikipedia.org/wiki/Solar_eclipse_of_July_2,_2019
  7. Website: https://www.history.com/news/how-5-ancient-cultures-explained-solar-eclipses
  8. Website: https://www.britannica.com/list/the-sun-was-eaten-6-ways-cultures-have-explained-eclipses