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

A paleomagnetist on board the JOIDES Resolution ocean drilling vessel

I was having a shower at the beginning of our last day on the ship- warm and comfort shower- and suddenly I smell something different, something like mold. I come out to the deck to realise that we have docked in Reykjavik, that it was the smell of land, the smell of the end of our two months expedition spent in the middle of the North Atlantic Ocean. A turmoil of feelings where silence would prevail. The entire scientist staff, the technical staff, some of the crew, the Capitan, we were all standing still, under a Nordic cold sun, watching the docking operations. The ever-changing colour of the Ocean turned to dark green port-like waters, full of birds, docks and ducks, land all around! It has been two months without seeing (and smelling) land.

We were coming back from our two months sailing in the legendary ship, the JOIDES Resolution (JR), for the International Ocean Discovery Program (IODP), Expedition 395 “Reykjanes Mantle Convection and Climate: Mantle Dynamics, Paleoceanography and Climate Evolution in the North Atlantic Ocean” with Ross Parnell-Turner from Scripps, California, Anne Briais from Toulouse in France as Chiefs, and Leah LeVay from IODP Texas A&M University as Project Manager/ Staff Scientists. We should have sailed in 2020 but because of the global Covid-19 pandemic, the JR Expedition sailed with only a few technical staff and became Expedition 384; one year later the expedition was postponed, becoming Expedition 395C, with only Leah as a Science Staff. Finally, this year, the entire Science Staff could sail. After a good amount of last-minute shopping, including chocolate, tea, biscuits and a hard disk, we set sail from the Ponta Delgata port in Sao Miguel (Azores, Portugal) on the 12th of June to drill a transect of 4 out of the 6 sites originally planned (2 were completed during Expedition 395C) from the East to West in the North Atlantic Ocean, south of Iceland. 

My job as a shipboard paleomagnetist was to measure all the sediment and hard rock cores in the Superconducting Rock Magnetometer to reconstruct the Earth's magnetic field changes in polarity to provide an age of the sediments. We compare these polarity changes recorded in the oceanic sediments (normal polarity is like the present day setting while the reverse polarity is when the North pole flips to the South Pole) with a global reference scale (called Geomagnetic Polarity Time Scale; Ogg 2020) to estimate the age of the sediments, and then we combine the paleomagnetic observations with the encounters of microfossils which also provide an independent age. We had 12 hours shifts and at the end of each shift (at noon and at midnight), we had a crossover meeting with all the other groups of scientists- the sedimentologists, the physical properties scientists, the geochemists, the stratigraphic correlators, the palaeontologists, us the paleomagnetists, the outreach officer, the staff scientists and the two chiefs. 

My typical day started with a one hour gym session in the morning, breakfast/lunch (which was always delicious), crossover meeting with my counterpart in the same role, Sarah, and then here we go, measuring all day meters and meters of ‘boring’ muds. I say ‘boring’ as their properties, colour, granulometry did not change much, but what I really mean was ‘amazing’ and ‘ideal’ for paleomagnetic studies as they require homogenous lithology and continuous sedimentation to capture with a clean signal all the polarity changes! Do not think that Sarah and I did all by ourselves... An amazing team of technicians was always there, ready to help answer questions and fix some mistakes (yes, we make mistakes and it’s ok). For every week there was a weekly report, for every completed site there was a site report and site summary and a meeting with everyone else to share the fresh off the measurements and interpretation results. Yes, hard work! In a hectic around the clock pace of laboratory work, data interpretation and report-writing, science was unveiling under our amazed eyes. Fuelled by coffee, music and peer comfort with frequent and short breaks (and a longer one for lunch/dinner), we made it! We drilled all the sites, exceeding the expectations, drilling more than 4 km of sediment cores, and 120m of basalts, nearly breaking the record of the deepest site ever drilled in one expedition. The Ocean was clement, calm for most of the time, blue, grey, silver, black, flock of birds were around us and some cetaceous visited us. It was simply an amazing experience, for the amazing group of scientists bringing their different expertise to the table, to achieve the expedition's goals and advance science…but I am sad that this program will end in just nine months.

That’s it. The JR needed repairs, but the main funding body cut the expenses out and none of the other international contributors stepped up to challenge. Nobody else will be able to sail on the legendary JR, breaking the boundaries of science by deep ocean drilling. We take comfort that the legacy remains for future scientists, of many kilometers of rock in the Core repositories of College Station in Texas and in Bremen but the specialised expertise to conduct a state of art floating laboratory are sadly lost, forever.

by Dr. Anita Di Chiara (she/her)


INGV - Rome

One of the crew on the JR Expedition 395




Photo Credits-
1 and 2: Jen Field, Outreach Officer
3: Dr. Sevi Modestou, shipboard sedimentologist

'Goescience Connections' in Braga Science Film Fest

The IUGG funded short documentary 'Geoscience Connections' that showcases the evolution of Earth with an analogy of human growth is all set to premier at the Braga Science Film Festival. The movie focusses on the science that is covered under the IUGG umbrella by its 8 different associations.

The festival is online from 18th to 26th November and free! Also, don't forget to vote for Geoscience Connections for the Audience Award! The movie can be found online at the IUGG channel as well.

Keep a look out at the IAGA and IUGG YouTube channels for an updated version of the movie where early career scientists from the 8 associations talk about the science that happens in the interior and on the surface and beyond.

Learn more about this outreach project as well as others here.

Debunking a Pillar of Ionospheric Science, and Building a New One: Episode I

Dear reader, I’m excited to try this non-traditional strategy, the thing they call a blog (honestly!), to tell you about my research into the foundations of ionospheric physics. But I suppose I should first tell you who is talking. After listening to Joan Baez sing at my elementary school, protesting the war in San Francisco with my mother, climbing over a fence because she was scared of the batons, swimming naked in a river with my entire 8th grade class, shocking the head of the math department at Palo Alto High School, working as a carpenter, out of a Volkswagen Bug, having my Fiat pulled out of a ditch by the man who made the first computer mouse (Figure 2 below) in his garage, designing my own religion, seeing people die who shouldn’t have died, working as a microwave engineer, marrying a much more conservative Chinese woman, having it work out, earning a Ph.D. in quantum gravity, and becoming the father of two hims, each amazing in their own way, I found myself trying to break into the field of ionospheric physics as a compromise approach to earning a living— at that same research lab where that wooden computer mouse arrived the next morning for testing (SRI International, where I have worked for 23 years).

Although I didn’t have time to worry about it back then, I noticed that while the magnetospheric people were all about MHD waves, there was no talk of what became of these waves when they entered the ionosphere. In the ionosphere, it was all about electrostatic theory, which made things very simple and easy. After spending a little while looking for an explanation, I quickly gave up. Quite a few years passed before I realized that I might actually be able to bridge this gap. My 2016 paper got great reviews, but was met with a deafening silence. My second paper did not get great reviews. I suspect a few of those referees had to be rushed directly to the hospital. Thank you to those few who supported me! But since I am given confidence by my rigorous education in physics and mathematics, and since the negative reviews were just sour grapes, it’s blogs away. You might now notice a slight change in tone.

The interaction of the magnetosphere with the ionosphere and atmosphere involves electromagnetic energy incident from the magnetosphere (for example as shown in Figure 1 on top left), which is output from an empirical Poynting flux model made from FAST satellite data (Cosgrove et al., 2014). The energy is dissipated by means of currents that flow through the ionospheric conductance, which arises because of the high rate of collisions with the neutral atmosphere, so that the currents cause heating and acceleration of the atmosphere. Various effects flow from this, with a particularly notable one being disruption of satellite orbits. Thus, it is important that we understand the physics that gives rise to the ionospheric conductance, which forms the inner boundary for magnetospheric modelling.

The ionospheric conductance has heretofore been calculated using a form of electrostatic theory that is very close to the textbook theory, where all time derivatives are set to zero and what remains of the equations of motion are applied to a boundary value problem. But since electrostatic theory is not valid in all cases, it is important to ask if we can show that it is valid for this ionospheric application, or, if not, to derive an electromagnetic calculation that can replace it.

The transition between electromagnetics and electrostatics is addressed in the transmission line theory of electrical engineering. Consider the simple “lumped element” circuit shown in the top panel of Figure 3, consisting of a switched harmonic source with internal resistance, driving a capacitor. In order to be properly causal, this circuit is generally analyzed by taking the Laplace transform in time, which provides a solution as a sum of steady-state and transient terms. In many cases we are only interested in the steady-state part, which leaves the usual idea of a capacitive admittance operating in a harmonic circuit (Yin iω0C, a positive imaginary number).

The terminology “lumped element” indicates that we are considering the capacitor to be very small, so that it doesn’t matter where the electrical connections are made to the parallel plates, and we can assume that the capacitor energizes everywhere all-at-once. But in reality when the switch is flipped, there is an electromagnetic signal that enters the capacitor on the side with the electrical leads, and then propagates across to the other edges, and bounces around until a steady state is reached. And depending on the size of the capacitor, there may be a portion of a wavelength inside the capacitor. When this happens the lumped element (electrostatic) analysis is too idealized to be of use.

To understand how this effect can be accommodated, consider the case of a capacitor that is long and thin, with the leads attached at the near end. Assuming that the signal cannot leak out and radiate away, this long and thin structure is a transmission line that is open-circuited at the far end. The signal propagates from the electrical leads to the far end where it reflects back, and then continues bouncing back and forth until a steady state is reached. Assuming there is only one propagating electromagnetic mode, the steady-state amounts to a superposition of two oppositely propagating waves, which are phased so that the current is zero at the open-circuited end.

From this description can be derived the well known formula for the steady-state input admittance seen by the source, which may be found, for example, in equation 3.88 from Collin (1966), and setting the load admittance to zero,where l is the length of the transmission line, Y0 is the characteristic admittance of the wave mode, and kz is the wavevector in the direction along the line (i.e., in the “parallel” or z direction). A schematic for the circuit with the open-circuited transmission line replacing the lumped-element capacitor is shown in the middle panel of Figure 3.

Since Y0 is usually a real number, the formula (1) provides that when the transmission line is short and the waves are not too lossy (i.e., kz is strongly real), then it does in fact function as a capacitor with admittance iY0kzl. But as the line gets longer the tangent function causes an oscillation between capacitive and inductive behavior, with near singularities where real(kz)l is a multiple of 90°. The singularities arise when the electric field of the reflected wave cancels that of the incident wave, where wave dissipation makes the cancelation imperfect, and is reflected in the imaginary part of kz. The famous “Smith chart” provides a graphical representation for lossless transmission lines that was a staple of microwave laboratories in the days before computers were widely available, which, by the way, was really not very long ago (bottom panel of Figure 3).

The ionosphere is not long and thin like this hypothetical capacitor. The capacitor was made thin to ensure that we do not question the coherence of the excitation produced by the electrical connections at the end. But as long as we stipulate that the excitation is coherent the capacitor can be made very wide, with electrical connections spread along its width. For example, the electrical connections could be phased so that they excite a simple plane wave, with some chosen transverse wavelength. In fact, assuming this very-wide geometry actually removes an approximation that we had swept under the rug, which is that to properly analyze the thin capacitor we should form a wavepacket in the transverse direction. If the capacitor is very wide, like, for example, the ionosphere, then there is no such approximation, and we can analyze one transverse wavelength at a time.

Thus, consider the gedankenexperiment shown in Figure 4, where the ionosphere is simplified to be a uniform slab of collisional plasma, with empty space below. The middle panel of Figure 3 is now the electromagnetic equivalent circuit for this simplified version of magnetosphere-ionosphere coupling, with the ionosphere represented by the open-circuited transmission line. The downward looking input admittance for an incident plane wave is given by the same transmission line formula (1), where Y0 and kz depend on the frequency and transverse wavelength of the plane wave.

The real part of the input admittance is, of course, the ionospheric conductance. We can compare the input admittance to the well known electrostatic approximation, which is the field line integrated conductivity, σPl, where σP is the (zero frequency) Pedersen conductivity. Doing this we derive some preliminary criteria for electrostatic theory,where kz 2π/λz − i/ldzλz is the wavelength, and ldz is the dissipation scale length for the propagating electromagnetic mode.

To my knowledge, the last of the three criteria (2) was first derived by Cosgrove (2016), who named iY0kz the wave-Pedersen conductivity, since it replaces the usual (zero-frequency) Pedersen conductivity in an electromagnetic calculation of ionospheric conductance. Cosgrove (2016) also found that Y0 is strongly imaginary, while kz is strongly real, so that iY0kz is in fact strongly real, as expected for the ionospheric admittance. An important corollary comes from the tangent function dependence (1), which suggests the unexpected possibility that the ionospheric conductance could contain (near) singularities and change sign, if the parallel wavelength is ever comparable to the thickness of the ionosphere.

Does this ever happen? Does iY0kz equal σP? Is there really only one propagating electromagnetic mode in the ionosphere? What happens when the ionosphere is vertically inhomogeneous? Stay tuned for the next episode. But I’ll give you a hint, the answer is not boring, just ask those referees who are recovering in the hospital— on second thought, don’t ask them (Cosgrove, 2022).



by Russell Bonner Cosgrove





Collin, R. E. (1966), Foundations for Microwave Engineering, McGraw-Hill.

Cosgrove, R. B. (2016), Does a localized plasma disturbance in the ionosphere evolve to electrostatic equilibrium? evidence to the contrary, J. Geophys. Res., 121, doi: https://doi.org/10.1002/2015JA021672.

Cosgrove, R. B. (2022), An electromagnetic calculation of ionospheric conductance that seems to override the field line integrated con- ductivity, Zenodo and ArXiv, doi: 10.48550/ARXIV.2211.10818, 10.5281/Zenodo.7416494.

Cosgrove, R. B., H. Bahcivan, S. Chen, R. J. Strangeway, J. Ortega, M. Alhassan, Y. Xu, M. V. Welie, J. Rehberger, S. Musielak, and N. Cahill (2014), Empirical model of poynting flux derived from fast data and a cusp signature, J. Geophys. Res., 119, 411–430, doi: https://doi.org/10.1002/2013JA019105.