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

On the connection between Martian global dust storms, waves, and water escape

Mars is the second most studied planet in the universe. Owing to great progress in observational and modeling techniques, fundamental atmospheric processes can be studied in great detail on Earth, which helps us study similar physical processes in other planetary atmospheres. On Earth, we take it for granted that there is plenty of water on the surface and atmosphere. On Mars, the question of what happened to (liquid) water is an exciting aspect of Martian climate science. It is thought that the early Mars used to have more habitable conditions with plenty of water on its surface and in its atmosphere. Studying habitability of a planet is to a large extent related to characterizing its atmospheric circulation patterns (winds) and thermal structure (temperature), which are important factors that control the presence and distribution of water. Probably one of the first things researchers seek to find on other planets in the Solar System and beyond is others forms of life. The common sense suggests that where there is a sufficient amount of liquid water, there could also be life. Why we look for life in the universe is, I guess, a philosophical question. 

On Mars, global dust storms are reoccurring phenomena and atmospheric gravity waves, generated by a variety of meteorological phenomena in the lower atmosphere, continuously populate the whole atmosphere system. Gravity (or buoyancy) waves are essentially small-scale short-period variations in atmospheric parameters such as winds, temperature, density, and pressure. A recent study based on (MAVEN) Mars Atmosphere Volatile Evolution Mission observation showed that during global dust storms, thermospheric gravity wave activity nearly doubles. It is quiet fascinating that processes taking place on the surface of a planet can influence upper layers of the atmosphere 200 km above the surface. This vertical coupling is meanwhile a major field of research in atmospheric sciences. This research finding immediately raises the question of how the processes of dust storms, gravity waves and Martian atmospheric escape are interrelated. 

This brings me to my main motivation to write this contribution in a recent science perspective article, in which I proposed that lower atmospheric gravity waves are a key player in shaping Martian water escape especially during global dust storms. Gravity waves are probably the missing puzzle piece in the context of Martian water cycle. Gravity waves shape the circulation and thermal structure of the Martian middle and upper atmosphere during all seasons. By influencing the mean meridional circulation (north-south winds) and upward winds on Mars, they can control the degree of water vapor transport from the mesosphere to the thermosphere, where water can be dissociated to hydrogen and oxygen. Hydrogen, the lighter species of the both, can easily escape to space. During global dust storms an increased amount of thermospheric gravity wave activity in form of increased temperature perturbations implies enhanced Jeans escape, since it is related to temperature variations. This can lead to an irreversible loss of hydrogen into space, depleting the atmosphere of water constituents. Over the course of many million years, global dust storms together with enhanced atmospheric wave activity could have diminished Martian atmospheric water reservoirs. Coordinated observational and modeling studies are needed to provide further insight into the complexity of water transport and loss on Mars.

After receiving his Ph.D. in physics from the University College London, UK, in 2009 in physics, Erdal Yiğit worked as a researcher at the University of Michigan (2009-2012) and UC Berkeley (2012-2013). He joined George Mason University as a faculty member in 2013; was granted tenure in 2018, and is currently working as an Associate Professor of Physics. He is the recipient of the 2016 Zeldovich Medal jointly presented by COSPAR and the Russian Academy of Sciences for his significant contributions to the study of coupling between the lower and upper atmospheres on Earth and Mars by gravity waves.


PhD in IAGA #1

IAGA has a lot of different scientists working on various topics. In this series of blogs, we will introduce some topics that are being worked on by PhD students. Hopefully this will give a better picture of the work being done in the field and encourage more early career researchers.

Paweł Jujeczko is a PhD candidate working in the Space Research Centre at the Polish Academy of Sciences. He says:

My research topic concerns the physics of Transient Luminous Events (TLEs). For those not familiar with that abbreviation, TLEs are some various phenomena that occur over very powerful thunderclouds (~10 to 100 km above the ground). In my research I model the behaviour of a TLE called "sprite" with a multi-processor code which works within the kinetic plasma theory. I try to model an instability that is possibly present in a plasma of TLE conditions or in simpler words, I try to tell why sprites look like these on the picture here.

Credit : https://apod.nasa.gov/apod/ap191008.html

Magnetic Field : Sun

Just like a planetary dynamo generates a magnetic field inside the planet, solar dynamo is responsible for the solar magnetic field. The Sun is composed of plasma, i.e, charged particles, which in motion produce magnetic fields. This field is carried away from the sun towards the planets in all directions by the solar wind, and is called the interplanetary magnetic field (IMF). Two interesting phenomena related to the field are its variation and shape.  

Interplanetary magnetic field extending out from the Sun. Credit: Vallée, J 1998

The solar magnetic field acts as a bar magnet with two poles. These poles are observed to flip regularly every 11 years. This variation is termed as a solar cycle. The solar minimum, when the field is weak, is considered the start of a solar cycle. The sunspots are lowest during this time. Sunspots are dark spots observed on the surface where the magnetic flux is very high (over 0.2 Teslas).

Number of sunspots vs time depicting solar cycles. Credit: ESA/NOAA.

The IMF extending out from the sun with the solar wind travels as a rotating spiral due to the spinning of the sun. This shape is known as the Parker spiral. The sun rotates around every 24 days at the equator and every 35 days at the pole. On average, this is taken to be 27 days and is known as the Carrington rotation.

Image Credit: NASA

The solar magnetic field and its related phenomena are active topics of research. There is still a lot to find and understand! 

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.



EGU Early Career Scientist Award (EMRP): Richard Bono

I am a Leverhulme Early Career Fellow working on research questions which bridge core processes, such as the geodynamo, to crust-to-space effects, including magnetic shielding and the evolution of life. Currently, I work in the Geomagnetism Laboratory at the University of Liverpool and in January 2022, I will be joining the Earth, Ocean and Atmospheric Science Department at Florida State University in Tallahassee, Florida. I earned my PhD in 2016 at the University of Rochester advised by Prof. John Tarduno, where I also earned my bachelor’s and master's degrees. In addition to pursuing my research, I also currently help to maintain the PINTdb.org paleointensity database and assist in organizing MagNetZ, an online seminar for the paleomagnetic community. 

My passion for geology is centred on the field of palaeomagnetism – the recognition that the magnetic record stored in rocks could act as a compass or a clock going back through geologic time inspired my pursuit in addressing questions about Earth’s interior across deep time. Through field work, careful laboratory experiments, statistical modelling and numerical simulation, I try to understand the fundamental properties and behaviour of Earth’s liquid outer core. 

As part of the DEEP group, I develop statistical paleomagnetic field models as part of a multidisciplinary team of geophysicists, geologists and dynamo modelers. These statistical models are used to characterize and test hypotheses related to long term geomagnetic field evolution, and aid comparisons between observational data to numerical dynamo simulations using Earth-like configurations. 

Field Work, Arctic, 2012. Credit : https://www.richardkbono.org/
Prior research focused on using single crystal palaeomagnetism and electron microscopy to investigate questions about how terrestrial planetary interiors evolved over time, the impact of this evolution on planetary surfaces, potential implications for the evolution of life and habitability, and fundamental capabilities of single crystals as magnetic recorders. This work resulted in some of the oldest magnetic records sampling the Hadean using zircons from the Jack Hills in Australia, the weakest magnetic records sampling the Ediacaran, as well as extra-terrestrial materials from pallasites and lunar samples. 

My work has involved a wide range of disciplines, with collaborators from geochronology, mantle modelling, plate reconstructions, mineral physics, electron microscopy, and numerical modelling communities. The broad implications of the research are as follows: the habitability of a planetary body is largely understood to be determined by its ability to retain liquid water on its surface. To maintain the physical conditions required to preserve liquid water on the surface, the planet must host an atmosphere, which is vulnerable to solar erosion over geologic timescales. Preserving the atmosphere from cosmic radiation requires a planetary magnetic field which shields the atmosphere, allowing liquid water to remain present on the surface. Therefore, understanding the conditions required to generate and maintain a dynamo in planetary bodies is crucial to gaining insight in the dual evolutions of Earth’s life and dynamo.

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;


    {  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.