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Last Updated: 05/26/2022


Version: 1.0

FIDO is a tool that allows for comparison of a simple flux rope model with in situ observations. The user-provided the location, orientation, and size of the flux rope, which determines the trajectory of a spacecraft through the flux rope. A simple flux rope model, typically the Lundquist force-free flux rope, can be used to convert the spacecraft path through the torus into an in situ magnetic field profile. While the FIDO was designed to work with the coronal CME deflection model ForeCAT, the inputs can be taken from anywhere, but it does use the same torus shape as ForeCAT to represent the flux rope.


Here is a list of the parameters that can be passed to FIDO via the input text file, as well as a brief description of each. The value in brackets indicates the default value when the parameter is not included in the input file.

  • CME lat: The latitude of the nose of the CME, which is the center grid point and farthest point radially, given in degrees in Heliocentric coordinates. [0°]
  • CME lon: The longitude of the nose of the CME, given in degrees. Any Heliocentric longitude system can be use (Carrington or Stonyhurst) but it should be the same as used for the Earth's longitude. [0°]
  • CME tilt: The orientation (in degrees) of the CME torus ranging between ±180°. This is measured by the angle between the toroidal axis and the solar equator, with positive values measured counterclockwise from the west direction (i.e. pointing north is 90°). This direction corresponds to the direction typically used in the literature, but different authors may have different conventions. [0°]
  • CME AW: The angular width of the CME in degrees, measured from nose to flank. Technically this is half of the full angular width (i.e. from flank to flank), but is what is typically reported and matches the GCS reconstructions. FIDO cannot use angular widths greater than 90°. [45°]
  • CME Ashape: The ratio of the CME height to the CME width. Reasonable values would be between about 0.5 and 1.5, but there is no strict limit. [0.75]
  • CME Bshape: The ratio of the CME cross-sectional width to the CME width. This must be lower than 1. [0.35]
  • CME vr: The radial speed of the CME in km/s. This is equivalent to the speed of the CME nose, not the average speed over the full CME, which would vary depending on the trajectory through the CME. Caution should be applied when pulling values from observations to make sure that the appropriate value is used. [440 km/s]
  • CME B0: The magnitude used in the Lundquist flux rope model, in nT. The sign indicates the toroidal magnetic field direction, either parallel or antiparallel to the toroidal direction. If Autonormalize is selected then the magnitude is ignored but the direction still affects the results. [25]
  • CME pol: The handedness of the flux rope with 1 indicating right-handed and -1 indicating left-handed. [1]
  • tshift: An offset used to adjust the start time of the modeled CME. FIDO is set to automatically align the front of the modeled results with the value given in CME start. This parameter shifts the modeled CME by the given number of hours. This parameter is typically not needed or used, but is still included. [0 hours]
  • Earth lat: The latitude of the Earth in Heliocentric coordinates. If considering a target other than a near-Earth satellite then the latitude of that satellite. [0°]
  • Earth lon: The longitude of the Earth (or other target) in Heliocentric coordinates. As with the CME longitude, any reference point can be used for zero longitude, the important factor is the relative difference between the two longitudes. [0°]
  • CME start: Day of year corresponding to the start of the in situ CME. This can be updated from the initial value, the range of the plot window will not change but the vertical line will move and the calculations will reflect the change. FIDO will not run if it is set outside the plot range. FIDO automatically sets the plot range as three hours on either side of the initial start/stop times so if these values need to change more than this the initial text file should be updated. [none]
  • CME stop: Day of year corresponding to the end of the in situ CME. Same behavior as CME start: [none]
  • Autonormalize: Option to scale the total magnetic field strength to automatically match the observed magnetic field strength. The autonormalize value is chosen to match the average of the observed and simulated total magnetic field strength during the four hours in the center of the CME. This can be set to True or False. [False]
  • Launch GUI: An option not to launch the GUI and simply save the results automati- cally instead. This can be useful for running multiple simulations from a bash script. [True]
  • Save Profile: Only a text file option, there is no corresponding button in the GUI. When set to True it will output a simple text file with FIDO results. [False]
  • Expansion Model: The mode of expansion, this can be set only to "Self-Similar" or "None". [None]


FIDO returns the fractional day of year, and Bx, By, and Bz in GSE coordinates for the satellite's path through the CME. It also calculates a score describing the quality of fit of the model to to the observations.

Model is time-dependant.


  • Solar
  • Heliosphere / Inner Heliosphere

Space Weather Impacts

  • Near-earth radiation and plasma environment (aerospace assets functionality)


  • Coronal Mass Ejections
  • Coronal Mass Ejections Propagation



Code Languages: Python

Public Repository: https://github.com/ckay314/FIDO


Publication Policy

In addition to any model-specific policy, please refer to the General Publication Policy.