February 3, 2017, 1:00 pm - 2:00 pm
February 3, 1:00 pm - 2:00 pm
The Near-Earth Magnetic Field and how it is Modeled within a Comprehensive Framework
Terence J. Sabaka (61A, Terence.J.Sabaka@nasa.gov)
The near-Earth magnetic field (< 1000-2000 km altitude) is comprised of a superposition of contributions from many different current sources located, for instance, in the core, lithosphere, ionosphere, magnetosphere, ocean, Earth's outer conductive layers, and even within satellite sampling shells. In order to study these sources it is necessary to separate these various fields using direct magnetic measurements by solving an inverse problem. Our group at GSFC has led the way in developing a modeling approach called 'Comprehensive Inversion' (CI) that parameterizes all of these sources and subsequently co-estimates them in order to achieve optimal separation. This has allowed us to extract fields that no other models have been able to do, such as that of the oceanic M2 tide. This has led to an exciting new concept called 'Dynamic Field Modeling' (DFM) that we hope to realize at GSFC where the CI empirical core parameterization is replaced with a dynamic representation from the MoSST geodynamo model that will hopefully allow for better field forecasting via data assimilation. This talk will discuss the CI approach, its benefits, and how it ties into the DFM idea.
MoSST and MoSST_DAS: CCM Tools for Solid Earth and Geomagnetic Forecast Research and Application
JWeijia Kuang (61A, Weijia.Kuang-1@nasa.gov)
The Earth's intrinsic magnetic field, i.e. the field that is generated and maintained by convection in the Earth's fluid outer core (geodynamo), has been in existence over much of the Earth's history. It changes over broad spatial and temporal scales, due to complex dynamical and chemical properties in the deep Earth. Therefore, it has remained one of the major sources to understand the solid Earth and its evolution history. Studies of geomagnetic field have been traditionally branched out in two distinct paths: (1) modeling, understanding and interpreting geomagnetic measurements from ground observatories and satellites in orbits; (2) understanding the origins and the mechanisms of geomagnetic secular variations (SV) via numerical geodynamo simulation. A more recent development, originated from Core and Crustal Magnetics (CCM) group in GSFC, is to use geomagnetic data assimilation to take advantages of both approaches for better modeling geomagnetic field and geodynamo, and for creating new opportunities in research and application, such as accurate geomagnetic forecasts (and hindcasts). In this presentation, I will describe MoSST and MoSST_DAS, the geodynamo model and the geomagnetic data assimilation system developed in house, and some of their results and applications.
Modeling global geomagnetic fluctuations due to near-surface sources
Robert H. Tyler (UMCP, Astronomy, and NASA GSFC 61A; email: robert.h.tyler@nasa.gov)
Fluctuations are observed in the geomagnetic field that are due to a variety of sources spanning a broad range of time and space scales. Interpretation of these fluctuations can provide monitoring of many processes occurring within the Earth System. Because many of the various signals involve overlap in time and space scales, sophisticated modeling is required to separate these various signals and invert to infer the associated underlying sources. Here I will primarily describe theoretical and numerical modeling of global-scale geomagnetic variations due to near-surface (upper mantle, ocean, atmosphere) electric current sources. A prominent component of these variations is due to solar and lunar tides in the oceans and atmosphere. Much progress has been made recently in modeling these fields: A very fast global electromagnetic induction model has been developed that is also dynamically consistent with ocean flow models as well as a recently-compiled global data set of ocean electrical conductivity. This forward-modeling capability together with geomagnetic data from land and satellite observatories provides an opportunity for remote sensing the near-surface sources and ultimately important parameters such as electrical conductivity, ocean heat content, and ocean flow.
