A Novel Physics-Based Functional Form for the Magnetopause Shape
Abstract
We present a new model for the shape of the magnetopause using a closed-form analytic function known as a tractrix. We derive this shape from several physics-based underpinnings, eliminating the need for fitting ad-hoc functional forms that, while convenient, are not physically motivated. One feature of the magnetopause that our model predicts is that the magnetotail flares outward until it reaches a constant width, a fact that has significant observational evidence but is seldom represented in functional forms of the magnetopause shape. To optimize the parameters of this model, a dataset of over 13,000 magnetopause crossings from THEMIS/ARTEMIS, Cluster, Geotail, Interball, and several other spacecraft is utilized. Using a Bayesian approach combined with a Markov Chain Monte Carlo (MCMC) method to estimate the posterior probability distribution in parameter space, we determine the maximum likelihood parameters for our model that optimize its performance for our dataset. We compare our model's performance to that of other popular models of the magnetopause, with a focus on their relative performances along the magnetotail, and show that it outperforms models that assume the tail flares outward to infinity at far distances. Our optimized model more accurately predicts magnetopause position along the tail than other popular static analytic magnetopause models, while still being easy to implement for a variety of applications.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMSM0180009O
- Keywords:
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- 2736 Magnetosphere/ionosphere interactions;
- MAGNETOSPHERIC PHYSICS;
- 2740 Magnetospheric configuration and dynamics;
- MAGNETOSPHERIC PHYSICS;
- 2756 Planetary magnetospheres;
- MAGNETOSPHERIC PHYSICS;
- 2794 Instruments and techniques;
- MAGNETOSPHERIC PHYSICS