• Photo by Nicolas J Leclercq on Unsplash
  • Photo by Nicolas Tissot on Unsplash
  • Photo by NASA on Unsplash
  • Photo by USGS on Unsplash

From scientists to everyone: the IGRF Model

In IAGA there is a group called V-MOD: Geomagnetic Field Modeling, part of Division V. The aim of this group is "to promote and coordinate international efforts to model and analyze the internal geomagnetic field and its secular variation on both global and regional scales". 

The main result of their efforts is the IGRF model. IGRF stands for International Geomagnetic Reference Field, and is a standard mathematical description of the Earth's main magnetic field and its temporal variation, called secular variation. IGRF is widely used in a multitude of different studies, such as the Earth's interior, the crust, the ionosphere and magnetosphere. It is also used in satellite attitude determination and control systems and other applications requiring orientation information. 

The model is the product of a collaborative effort between magnetic field modellers and the institutes involved in collecting and disseminating magnetic field data from satellites and from observatories and surveys around the world. It is a voluntary work for the benefit of all. Each time a new model is to be obtained, different teams of scientists come together and propose different candidate models. The final model is usually a mean or median of all candidate models and some kind of weighting scheme may also be applied. The overall process is described in papers for each one of the candidate models, the evaluation process and finally a paper describing the final model. 

Map of the declination at 2020.0 as given by IGRF-13 (Alken et al., 2021)
The Earth's field changes continuously and in order to account for temporal changes on timescales of a few years, the IGRF is regularly revised, typically every 5 years. The years for which coefficients are provided are called model epochs. The coefficients of a certain epoch represent a snapshot of the geomagnetic field at that time, and can be labeled either as a Definitive Geomagnetic Reference Model (DGRF, which are unlikely to be improved in future IGRF revisions) or as an IGRF. 

The last generation, IGRF-13, was finalized in December 2019 by a task force of group V-MOD. It provides a DGRF model for epoch 2015.0, an IGRF model for epoch 2020.0, and a predictive IGRF secular variation model for the 5-year time interval 2020.0 to 2025.0. The main field coefficients describe the spatial variation of the field to a maximum spherical harmonic degree and order of 13, while the secular variation extend to a maximum degree and order of 8. 

Satellite data, such as the one provided by the ESA Swarm mission and the ground observatory network were crucial to the latest IGRF generations. Data from other satellite missions were also used. 

The coefficients to calculate the model may be found in the designated paper (Alken et al, 2021) and also online in digital form along with the software to compute magnetic field components at different times and spatial locations. 

Where to find the model and other information:

- model IGRF-13 paper: https://doi.org/10.1186/s40623-020-01288-x 

- model issue, with candidate models' papers and evaluation process paper: https://earth-planets-space.springeropen.com/igrf13 

- working group V-MOD webpage and model: https://www.ngdc.noaa.gov/IAGA/vmod/igrf.html

 



After a master in Geophysics from Portugal, Diana Saturnino got a PhD in Geomagnetism and continued working on the subject for a few more years in Denmark and France. Now she's looking for different adventures. She can be contacted via e-mail here.



 

 

 

Code for writing an Academic Article

start writing; 

revision_new = 0;

do

    {  revision_old = revision_new;

        if  ( (mind == full) || (mind == blocked) )    procrastinate ++;

        prepare draft;

        send to co-authors;

        address all comments and revise;

        revision_new = revise; 

    } while  (revision_new < satisfied);

submit paper;


for  (paper = submit; paper <= final; paper ++)

    {  paper submitted in journal;

        editor assigned;


        if  ( paper == rejected ) 

            printf ("\n The paper was rejected. Revise and submit to another journal. \n"); 


        else if  ( paper == passed to reviewers )

            { wait for eternity;

               address reviewer1;

               address reviewer2;

               don't hate reviewers; address reviewer3;

               revise for the billionth time;

               submit paper; 


               if  ( paper == still rejected ) 

                    printf ("\n The paper was rejected. Add more data, revise and submit to another journal. Try not to overthink about your life and curse your luck. \n");

               

               else if  ( paper == accepted )

                    wait for eternity;

                       pay fees to publish your own work;

                       printf("\n Celebrate. Go back to work on another paper. \n");  }

    } }



Shivangi Sharan is a second year PhD student at the Laboratory of Planetology and Geodynamics in France. Her research focusses on the study of the magnetic field of Mars and to infer its internal structure from it. She is an active member of the IAGA Blog Team and can be contacted via e-mail here.



  

                                                  

Aurorae Events of November 3-4, 2021 : A Summary

People up and down the United Kingdom have been able to see the northern lights this month- a rare occurrence, considering that the aurora borealis are only usually visible at higher latitudes (think Iceland, or northern Finland!)

So, what has been happening up there in space? For those of you readers that do not know about the origins of the northern lights, what causes them is what is commonly known as the solar wind- a string of charged particles which stream outwards from the sun constantly in all directions. These particles then interact with the Earth’s magnetic field, causing them to curve to higher latitudes where the magnetic field lines pass through the Earth’s atmosphere. As these particles enter the upper atmosphere, they excite and ionise the upper layers of gases, which in turn causes light emission- the aurora borealis in northern latitudes, or aurora australis in southern latitudes. This is not unique to our planet- Jupiter has aurora as well, for example.

Demonstrating how the aurora form. Particles from the Sun are deflected towards the poles. The early November event also saw enhanced aurora in the southern hemisphere, including sightings in New Zealand. Credit: NOAA

The widespread aurora seen on the week of the 1st of November was caused by exciting solar activity. The sun released an X class flare (the highest class) on Thursday 28th October, and we saw some geomagnetic activity here on Earth on the 30th-31st October (though, according to the British Geological Survey, most of the effects of the flare and the associated coronal mass ejection missed the Earth to the south). The 03-04 November event was mostly due to a coronal mass ejection and M-class flares (the second highest class) which occurred on the 2nd of November on the surface of the sun. Though the speed of propagation through the solar system is very fast (hundreds of km per second, in fact), it still takes several days for the effects to reach us on Earth. The effects were strong and did interact with the Earth’s magnetic field rather than missing it (in 3D space, it is very likely that any given event will not interact with us, considering the Earth is so small). In addition, the direction of the IMF (interplanetary magnetic field) was in the direction of the Earth’s magnetic field, leading to a strong connection between the two and stronger space weather impacts.

Photo of Northern Lights over Derwent Water, Cumbria, early November 2021. Image Credit: Owen Humphries (PA).

On Earth, we experienced large differences in the geomagnetic field compared to quiet periods, which produced a high value of the Kp index (which we use to quantify the changes in the magnetic field).

The northern lights are, however, hit and miss. If there is cloud cover, or you are looking at the wrong time or in an area with a lot of light pollution, you may not see the aurora even if they are directly overhead. I found this, to my chagrin, when I went looking for this particular event with another colleague working in geomagnetism. However, when this happens to you, you simply need to come back another time. Aurora are rare at lower latitudes, but there will be another opportunity. Sometime in the future, you may yet see a faint, translucent green light on the northern horizon.

 

 


Samuel Fielding is a first year PhD candidate at the University of Edinburgh, working on the real-time forecasting of space weather using machine learning and satellite data. He can be contacted via e-mail here.

 




WDC archive - Preservation of Old data

In 2020, the World Data Centers for Solid Earth Physics and Solar‐Terrestrial Physics (Moscow, Russia) continued the work on the “Preservation of Old Data” project, aimed at digitizing analog data from observatories into electronic documents by in‐line scanning. 

 

 

 

The data of the 8 ionospheric stations (43,500 documents) were transferred to a digital form. This includes the results of a vertical sounding of the ionosphere (tables and graphs of hourly mean values of the ionospheric parameters), measurements of absorption, ionospheric winds, atmospheric radio noise, parameters of electronic density of the ionosphere. 

 

 

Digital documents have been verified and edited. For the data in PDF format, the catalog and metadata have been compiled, a data archive has been formed and published on the website. The data archive for the hourly average values of the elements of the geomagnetic field, recorded by the former USSR observatories from 1957 to the beginning of the 90s, that had been previously fully scanned and translated into PDF files, has undergone verification process and editing. 

In 2020, 82 annual datasets of 4 observatories were checked, edited and added to the archive. Currently the time tables of the 26 observatories containing hourly average values of the elements of the geomagnetic field are ready and located in the WDC archive.




Contributed by the Chair of the Interdivisional Commission on History, Dr. Anatoly Soloviev, from the Geophysical Center, Russian Academy of Sciences, Moscow. The Commission encourages historical geophysical research and preservation of IAGA's history.

IAGA-IAPS Memorandum


 

IAGA and the International Association of Physics Students (IAPS) are taking joint efforts for academic growth by signing a Memorandum of Understanding. This has been done with the aim to establish future collaborations and to expand both the communities.


IAPS is an international, student-run educational association, which aims to encourage physics students in their academic and professional growth by developing an ever-growing worldwide community within which peaceful relations are established in a collaborative, diverse and friendly social environment.

The Naming Game : Moon Edition

What are moons? Moons are satellites that orbit around a planet. So, technically they'd be 'natural satellites of the planets' because "Moon" is just one, but, practically, don't we all just call them "moons"?! Currently, there are over 200 moons in our Solar System, and that's excluding the ones orbiting the dwarf or minor planets. 

Some moons have atmospheres, some have volcanic activities going on them and some even have oceans. Some moons orbit in direction of the rotation of planet and some orbit in opposite direction. But do you know how or what they are named?


The official names of celestial bodies are taken care of by the International Astronomical Union. Most of them are named after Greek and Roman mythology characters, but some are also named after literary characters.

While Mercury and Venus don't have any moons, our moon has many different names in different languages. The word "Moon" was named after two Latin words meaning 'to measure' and 'month'.

Mars, named after the Greek mythological God of war, Ares, has two moons -  Phobos and Deimos - named after the sons of Ares meaning 'fear' and 'dread'.

Jupiter has a plethora - 53 named moons and 26 unnamed ones. The planet is named after the Greek God, Zeus, and its moons are named after his lovers or descendants. Galileo first discovered the moons of Jupiter and hence the four biggest moons - Ganymede, Callisto, Io and Europa - are called the Galilean moons.

Saturn has such a large family of moons - around 82 which we know of - that there was a shortage for names. They were named after the Titans (children of Greek Gods Uranus and Gaia) and their descendants, but are now named also after the giants of the Norse, Gallic and Inuit mythology.


Uranus has 27 moons and they are named after Shakespeare's characters. A few are named after Alexander Pope's characters. Look them up to know if your favorite character made the cut; the maximum number coming from 'The Tempest'.

And finally, Neptune has 14 moons. Neptune, named after the Roman God of sea has its moons named after other Roman and Greek sea gods and nymphs.

Moons that are yet to be confirmed are named with a letter and year. 

Images : (1) Kevin Gill on Flickr. (2) Hubble. (3) Adobe Stock.



Shivangi Sharan is a second year PhD student at the Laboratory of Planetology and Geodynamics in France. Her research focusses on the study of the magnetic field of Mars and to infer its internal structure from it. She is an active member of the IAGA Blog Team and can be contacted via e-mail here.



  

IGY by ICH

A thorough insight into the International Geophysical Year (IGY) project from a 60‐year later perspective has been depicted by Y. Lyubovtseva, A. Gvishiani, A. Soloviev et al. in “Sixtieth anniversary of the International Geophysical Year (1957–2017) – contribution of the Soviet Union” published in the History of Geo‐ and Space Sciences journal (https://doi.org/10.5194/hgss‐11‐ 157‐2020). 

The IGY was the most significant international scientific event in geophysical sciences in the history of mankind. This was the largest international experiment that brought together about 300 000 scientists from 67 countries. Well‐planned activity of national and international committees was organized for the first time.


Read also about the "The IGY and Me" blogs published in our last blog here.



Contributed by the Chair of the Interdivisional Commission on History, Dr. Anatoly Soloviev, from the Geophysical Center, Russian Academy of Sciences, Moscow. The Commission encourages historical geophysical research and preservation of IAGA's history.