CGEM’s Summary

What is CGEM? Coronal Global Evolutionary Model or CGEM is a NASA/NSF funded Project between UC Berkeley, Stanford University and Lockheed Martin Space and Astrophysics Laboratory.

What is CGEM’s Goal? CGEM’s goal is to improve our understanding of the corona of the Sun — to develop and evaluate a model for the evolution of its magnetic field.

Why do CGEM? The most violent space weather events such as eruptive solar flares and coronal mass ejections are driven by the release of free magnetic energy stored in the solar corona. Once released this energy propagates through interplanetary space, frequently impacting the Earth’s space environment. How this energy  is stored? This is a fundamental question to predict space weather. Yet current data-driven space-weather models have been unable to realistically answer that.

Why now?

  • Recent  launch  of SDO/HMI makes  the  data  necessary  to  construct  better  coronal  models  regularly  available
  • Recent  theoretical  developments  make  it  possible  to  derive  electric  fields  from  HMI  data  sequences  using  Faraday’s  law  and  Doppler  data
  • Recent  computational  methods  for  evolving  the  coronal  magnetic  field  using  a  magneto-frictional  model  make  it  practical  to  evolve  the  coronal  magnetic  field  on  spatial  and  temporal  scales  that  are  useful

CGEM Components

  1. Develop enhanced processing and analysis of vector magnetic field and Doppler velocity data taken with the HMI instrument on NASA’s SDO Mission
  2. Use these processed data to derive the electric field in the solar photosphere (NOAA 11158 dataset)
  3. Using the photospheric magnetic and electric field vectors, evolve the overlying coronal magnetic field, using a ‘magnetofrictional’ model for its quasi-static evolution as energy builds up
  4. For magnetic field configurations that become unstable, use MHD models to evolve the solar corona, using output from the magnetofrictional model as an initial condition. For parts of the Sun for which no magnetic field data are available, a flux transport model will be developed and used to estimate the evolution of the magnetic and electric fields for the global version of the magnetic field model discussed below.

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