Frederik Dahl Madsen

It’s a beautiful place!

An unexpected benefit to visiting aforementioned supervisor is the scenic post-lunch runs around West Kirby

Despite train cancellations, I’m on my way to @liverpooluni.bsky.social to visit my geodesy-supervisor! Do quite enjoy working on the train these days

Do you need some WD40?

Are you an early career researcher in geophysics or astronomy? Come to our event in London in two weeks!

Give my supervisor a listen, as he excellently explains the south Atlantic anomaly in the geomagnetic field 🧲 🌍 @bgs.ac.uk

Very excited to be at the #DeepDyn dynamos in a nutshell workshop at @mpsgoettingen.bsky.social !

The most exciting thing, of course, is to learn how to use the #MagIC dynamo code. 🌍

Second most exciting thing is having vegan currywurst for lunch! 🌭

Disclaimer: It feels like the post description doesn’t match the article, but it was the article I wanted to repost!

Mosquitoes Discovered in Iceland for the First Time amid Rising Temperatures Bird flu surges and a government shutdown collide, complicating efforts to track cases and protect flocks.

Bird flu surges and a government shutdown collide, complicating efforts to track cases and protect flocks.

Graphic promoting the 'Early Career Event' Specialist Discussion Meeting arranged by the Royal Astronomical Society.

🧑‍🔬 Are you an early career researcher?🧑‍🔬

If so, we'd love for you to attend our early career event next month. It will feature a careers panel, networking opportunities and a discussion about the importance of effective communication for sharing research.

Book your spot at: ras.ac.uk/early-career...

Cycling out and home from the @bgs.ac.uk Lyell Centre is a pleasure this time of year 🌈🌅

Why is the Earth System Oscillating at a 6-Year Period? - Surveys in Geophysics A 6-year cycle has long been recognized to influence the Earth’s rotation, the internal magnetic field and motions in the fluid Earth’s core. Recent observations have revealed that a 6-year cycle also...

You are correct - the atmosphere also has 6-year periods - they co-exist with the ones we see from the core (which we would expect to exist, as per ex. Mound and Buffett 2003).

I can recommend this recent review that interprets all these signals holistically.
doi.org/10.1007/s10712-024-09874-4

The jury is still out as to why, but I suspect it arises from the gravitational coupling between the inner core and mantle

After that, the 6 year oscillation is still clear. It is well acknowledged that such a signal exists (see, for example, Holme and de Viron, 2013;Nature, or Rosat and Gillet, 2023;PEPI).

We remove the tidal contribution from the signal using the IERS reference tides, which do a very good job. We also clean the signal of atmospheric and oceanic contributions to length-of-day.

You are correct! That is why it’s very important to subtract the zonal tides before we do any analysis ☺️🌍

A graphic which says 'virtual program (Zoom) 27 - 31 October 2025), CTC x BAS BGS 2025, autumn virtual work experience week. Open to UK residents ages 14 - 19 (whether in school, college or not currently studying). Three logos are bottom right and to the left is a picture of safety goggles in a lab setting

Calling students from 14 - 19!

BGS & @bas.ac.uk are offering a 2 week virtual work experience event from 27 to 31 October.

We hope this will introduce students to the wonders of Earth sciences & the fascinating & varied careers available.

Apply:
sites.google.com/view/ctcport...

Variations in length of day (⁠ΔLOD) in milliseconds from modern data (1962 to 2025). (a) Tidally corrected LOD for the period 1962–2025 (referred to as raw ΔLOD), atmospheric angular momentum excitation functions (AAMF) for the period 1948–2025, and oceanic angular momentum functions (OAMF) from 1977 to 2025. Figure also shows ΔLOD corrected for AAMF, OAMF and tidal contributions, before and after a semiannual rolling mean is applied. (b) Power spectral density (PSD) for each curve shown in (a), showing energy in periods between 0 and 10 yr.

Published in #GJI Geophysical Journal International: "A recent interruption in the 6-year oscillation in length-of-day", Madsen & Holme. This is Fig. 1: read the paper at academic.oup.com/gji/article/... @oxfordacademic.bsky.social @royalastrosoc.bsky.social

Thanks for highlighting it! 🤩

This work was completed by me and one of my supervisors, Prof. Richard Holme from @liverpooluni.bsky.social

A recent interruption in the 6-year oscillation in length-of-day SUMMARY. Intradecadal variations in the length-of-day ($\Delta$LOD) can reveal changes in angular velocity interpreted as due to Earth’s core. Previous stu

🌍New Paper Alert🕰️

Our paper "A recent interruption in the 6-year oscillation in length-of-day" is finally out in #GJI @rasjournals.bsky.social.

Did you know that the length of a day changes every day?
We use this information to look at Earth's core.

#OpenAccess link here: doi.org/10.1093/gji/...

A little geodetic content from Lisbon for @hughpumphrey.bsky.social - found this pillar in the castle! Presumably a benchmark of some kind

We are expecting an increase in geomagnetic activity over the next few days due to increased solar activity.

A coronal mass ejection (CME) is expected to arrive this evening making STORM periods likely, potentially peaking at moderate (G3) or strong (G4) levels.

First day of #IAGAIASPEI25 done! It was so exciting hear about so much cool science today 🌏🧭🧲

And likewise, lovely to bump into you as well! What an unlikely place to meet a friendly face!

There’s no bag yet, but at least I’ve got fresh clothes now… see how long it’ll take KLM to find it!

Hope you’ll have a great rest-of-your holiday!

Arrived in Lisbon last night, super excited for #IAGAIASPEI25!

…now I’m just waiting for KLM to bring my luggage to Lisbon as well…
(Pastel de Nata to pass the time)

I missed this, but sounds good! Time-depending, I could definitely join, have not been there in a long time!

University of Aberdeen's Dr David Cornwell doing seismology-related outreach, which forms part of planned grant activities funded by the RAS.

Looking for funding for your outreach project or studies within astronomy and geophysics? We’re now accepting applications for our August grants round.

Learn more about the criteria and the application process at the link below ⤵️

ras.ac.uk/awards-and-g...

The amazing #Geophysics Treasure Hunt resource, developed by Esther Bull, is now available as an Open Educational Resource! It was a delight to supervise Esther, and I think the outcome was excellent!

#Outreach #OER #OpenEducation

📢 Leadership Update from SAGES!🌍

We’re thrilled to announce that Professor Brice Rea from the University of Aberdeen has been appointed as the new Director of SAGES, taking over in July 2025.