Global Assimilation of Ionospheric Measurements (GAIM)

Abstract

Our primary goal is to construct a real-time data assimilation model for the ionosphere-plasmasphere system that will provide reliable specifications and forecasts. A secondary goal is to validate the model for a wide range of geophysical conditions, including different solar cycle, seasonal, storm, and substorm conditions. OBJECTIVES We propose to develop a software program that will provide for a Global Assimilation of Ionospheric Measurements (GAIM). GAIM will use a physics-based ionosphere-plasmasphere model as a basis for assimilating a diverse set of real-time (or near real-time) measurements. The program will provide specifications and forecasts on a specified spatial grid that can be global, regional, or local (50 km x 50 km). The specifications/forecasts will be in the form of 3-dimensional electron density distributions from 90 km to geosynchronous altitudes (35,000 km). Auxiliary plasma parameters will also be provided, such as N m F 2 , h m F 2 , N m E, h m E, and slant and vertical TEC. In its specification mode, GAIM will provide quantitative estimates for the accuracy of the reconstructed ionospheric densities. The measurements GAIM will assimilate include: (1) Slant path TECs between 80-90 ground receivers and the Global Positioning System (GPS) satellites; (2) Occultation data from a satellite constellation such as COSMIC; (3) TECs associated with the CIT network; (4) Bottomside N e profiles from digisondes associated with the Air Force DISS network; (5) In situ plasma parameters from the SSIES instrument package on the DMSP satellites; and (6) Line-of-sight UV emissions and deduced plasma parameters from the Naval Research Laboratory's SSUSI and SSULI instruments. GAIM will have a modular construction, so that new data types can be readily assimilated when they become available. APPROACH Our approach is to use a two-step process to obtain a 3-D ionospheric reconstruction. First, certain data sets will be assimilated so that the inputs (neutral parameters, electric fields, precipitation) to the physics-based ionosphere-plasmasphere model can be adjusted, within expected errors, to match observations, and then the physics-based model will be run in order to obtain a 3-D N e distribution that is consistent with the measured inputs. This first step should result in realistic ionospheric density features. Next, this simulated ionosphere-plasmasphere system will be used as a starting point for an electron density reconstruction using all of the different data types that pertain to N e and a Kalman filter assimilation technique. The use of a simulated ionosphere-plasmasphere system will provide

Comparative Studies of Theoretical Models in the Equatorial Ionosphere

“…The first set is the non-self-consistent models that include the Space Environment Corporation (SEC) Ionospheric Forecast Model (IFM) [Schunk et al, 1997;Schunk and Sojka, 1998], the SEC Ionosphere-Plasmasphere Model (IPM) [Scherliess et al, 2004;Schunk et al, 2004], the SEC Low Latitude Ionosphere Sector Model (LLIONS) [Anderson, 1981;Schunk et al, 1997], the Air Force Research Laboratory physics-based model (PBMOD) [Retterer, 2005;Retterer et al, 2005], the GIP [Fang et al, 2009], and the NRL SAMI2 is Another Model of the Ionosphere (SAMI2) [Huba et al, 2000]. Important parameters of these non-self-consistent models are listed in Table 1.…”

Ionosphere‐Thermosphere Physics

“…The current global ionosphere and ionosphere-plasmasphere models [Bailey and Sellek, 1990;Millward et al, 1996;Richards and Torr, 1996;Schunk et al, 2004] are based on relatively simple mathematical formulations. Specifically, the adopted continuity, momentum, and energy equations are simplified by ignoring nonlinear and/or complicated terms.…”

“…As noted above, the four well-known physics-based global models of the coupled ionosphere-plasmasphere are based on a relatively simple diffusion formulation, which means that the nonlinear inertial term in the momentum equation (∂u/∂t + u&∇u) is not included [Bailey and Sellek, 1990;Richards and Torr, 1996;Millward et al, 1996;Schunk et al, 2004;Scherliess et al, 2004]. The neglect of this term is useful for numerical reasons, but there are two negative consequences.…”

“…Typically, the temperatures in the outer plasmasphere obtained from the global I-P models are too low (~4000-5000 K), whereas measurements indicate they are typically 8000-10,000 K [Titheridge, 1998]. To circumvent this problem, Schunk et al [2004] adopted the empirical plasmasphere temperature model developed by Titheridge [1998]. Although this temperature model is based on an extensive satellite database, it is simplified in that it is a static empirical model.…”

Integrated acoustics systems for ocean observatories

“…The atmospheric community demonstrated as early as 1993 the benefits of this data type in data assimilating models 13) . The U.S. Department of Defense is actively pursuing ionospheric data assimilation that will be using this and other GPS data 14) . Geodosists use a global array of GPS receivers to track the motion of tectonic plates in real time (millimeters per year).…”