[Baps] PLS 11/14 – Chi Yan - Planetary dynamos

[John B. Biersteker]

Hello planeteers,

We are very happy to announce that we will have Dr. Chi Yan<https://chiyan.me> from the Earth & Planets Laboratory at the Carnegie Institute joining us next week to talk about the planetary dynamos of Saturn and Mars. Please join us on Tuesday, November 14 @ 12:30 in 54-517 or on Zoom. As usual, lunch will be provided and we encourage arriving early to get food.

Chi will be visiting our department all day Tuesday and is available for meetings. If you’d like to sign up for an individual meeting, you can do so here<https://docs.google.com/spreadsheets/d/1TxdbkMat4Zp7lO6-JF1GH48wioLi0RBx4eX9VVM3lMc/edit?usp=sharing>.

Additional talk and Zoom information are below. We hope to see you there!

-John

=====
Planetary Dynamos: Case Studies for Saturn and Mars

Over the decades, space missions have revealed many planet/moons have or once had their own magnetic fields. These fields are generated deep within the planets’ interiors by a self-sustained dynamo process that involves complex motions of electrically conducting fluids in the presence of existing magnetic fields. Numerical simulations have shown that dynamo action is sensitive to variations of interior structures and boundary conditions (e.g., thermal perturbations) and would affect the resulting magnetic field we oversee beyond the surface. Diagnosis of the effect of specific properties and conditions are therefore useful for comparison to the observational data of planetary magnetic fields, providing information on their interior structures. Here I present two case studies:
      (1) the curious Saturnian dynamo
      For Saturn, the magnetic data from Cassini Grand Finale demonstrates that Saturn’s magnetic field is purely axisymmetric. This is problematic because Cowling’s theorem states that such a field cannot be maintained by dynamo action. Here I investigate that if the presence of a helium rainout layer at the top of Saturn’s dynamo region can resolve this dilemma by preferentially attenuating the non-axisymmetric magnetic field so that the field appears axisymmetric outside the planet. Using the characteristics of Saturn’s magnetic field, we are able to constrain properties of the deep interior of Saturn.
(2) the ancient Martian dynamo
Magnetic field observations from the MGS, MAVEN, and InSight missions reveal that a dynamo was active in Mars’ early history. The ancient martian dynamo is curious both spatially, i.e., the hemispheric dichotomy of the crustal magnetic fields, and temporally, i.e., the timeline of the martian dynamo history. Additionally, recent seismic measurements from the InSight mission revealed that Mars’ core has a relatively low density, implying the absence of a solid inner core throughout Mars’ history. Here I investigate the effects of thermal perturbations at the core mantle boundary on the morphology of the resulting field and compare those to dynamo models obtaining a small Earth-sized inner core.

=====
Zoom: https://mit.zoom.us/j/92448700577
PW: 54100
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.mit.edu/pipermail/baps/attachments/20231109/10f40a01/attachment.htm>