Work Description

Research Overview: Global Ionosphere Thermosphere Model (GITM) was used to simulate the geomagnetic storm on Sep 7, 2017 and study the segmentation of storm-enhanced plasma density (SED) plume into polar cap patches. GITM is driven by high-resolution coupled Block-Adaptive-Tree-Solar Wind-Roe-Upwind-Scheme (BATSRUS) and Rice Convection models (RCM) within the Space Weather Modeling Framework (SWMF). The simulation was done by Zihan Wang on NCAR's Cheyenne (https://www2.cisl.ucar.edu/resources/computational-systems/cheyenne) on January 2019. This work is supported by NASA Grant NNX14AF31G and NSF Grant AGS1400998.

Methods: GITM is a three-dimensional spherical grid that models the Earth's global ionosphere and thermosphere system self-consistently. In this study, the spatial resolution of GITM is set to 1 degree in latitude and 2 degree in longitude with 50 vertical levels (from 100 to 700 km). GITM allows different models of high-latitude electric fields, auroral particle precipitation, and solar radiation as inputs. In this study, the Flare Irradiance Spectral Model (FISM) is used to provide solar irradiance input for the whole simulation (http://lasp.colorado.edu/lisird/data/fism). FISM is an empirical model of the solar irradiance spectrum covering from 0.1 to 190 nm with 1 nm resolution and 1-minute temporal resolution. Using the high-resolution FISM model, the solar flare impact on the ionosphere and thermosphere can be captured. Various models of high-latitude electric fields and auroral particle precipitation can be used in GITM. The latest version of GITM is available at https://github.com/aaronjridley/GITM.

At first, GITM was run for two quiet days (Sep 4-5) to achieve steady state. During this stage, the Fuller-Rowell and Evans empirical model and Weimer empirical electric field model (https://ccmc.gsfc.nasa.gov/models/modelinfo.php?model=Weimer) are used as the precipitation and electric field input, respectively. The Fuller-Rowell and Evans model (Fuller-Rowell&Evans, 1987) is driven by Hemispheric Power (HP), which is found to be linearly related with auroral electrojet lower boundary (AL index) in empirical model. We use the observed AL index from the Kyoto World Data Center for Geomagnetism (http://wdc.kugi.kyoto-u.ac.jp/) to calculate the hemispheric power. The Weimer model is driven by the observed solar wind data from OMNIWeb. Starting from Sep 6 00 UT, the high-latitude driver is switched to the electric field and precipitation from the 2-way coupled BATSRUS and RCM models, as part of the University of Michigan Space Weather Modeling Framework (SWMF) (http://csem.engin.umich.edu/tools/swmf/). The coupled model is driven by the real solar wind data from OMNIWeb (https://omniweb.gsfc.nasa.gov/html/HROdocum.html). High resolution grid (1/8 RE) in the inner magnetosphere, magnetopause and current sheet has been implemented to better capture dynamic field-aligned currents (FACs) and precipitation structures.

File Inventory:
-3DALL*.bin files (4 total) - Output from GITM. binary files describing the neutral parameters in the ionosphere-thermosphere system; can be read with thermo_batch_new.pro and procedures within.
-3DION*.bin files (4 total) - Output from GITM. binary files describing the plasma parameters in the ionosphere-thermosphere system; can be read with thermo_batch_new.pro and procedures within.
-3d_mhd*.plt - Output from BATSRUS describing the plasma parameters, electric field and magnetic field in the whole 3D magnetosphere; can be opened with Tecplot (https://www.tecplot.com)
-it17*.idl files (3 total) - Output from the Ionospheric Electrodynamics module of SWMF. describe the 2D electrodynamics in the ionosphere; can be opened with Spacepy (https://pythonhosted.org/SpacePy)
-*.pro files (6 total) - Procedures used to open and read 3DALL and 3DION files. thermo_batch_new.pro is the main program. Other .pro files are functions in thermo_batch_new.pro.

Dataset citation:
Wang, Z. (2019). Space Weather Modeling Framework (SWMF) Simulation of Sep 7 2017 Geomagnetic Storm [Data set]. University of Michigan Deep Blue Data Repository. https://doi.org/10.7302/9097-z311

Reference:
Fuller-Rowell, T. J., & Evans, D. S.(1987).Height-integrated Pedersen and Hall conductivity patterns inferred from the TIROS-NOAA satellite data. Journal of Geophysical Research,92(A7), 7606.Retrieved from http://doi.wiley.com/10.1029/JA092iA07p07606.