Author: M. Wiltberger
Date: 08/01/2003
Note: Initial presentation using SPDX

Modified-By: M. Wiltberger
Date: 08/01/2004
Note: Integrated into CISM_DX

Modified-By: R.S. Weigel
Date: 06/01/2005
Note: Added Keywords and Acronyms and Test Your Knowledge sections. Modified test for consistency with Introduction labs.

Keywords and Acronyms:

MHD: Magnetohydrodynamics

LFM: Lyon-Fedder-Mobary MHD code

Control Panel: An interaction menu - see the list in the Interactor category in the Tools column.

Physics Background:
The following links were excerpted from the AFWA Space Weather Forecasting training material.

Magnetosphere: for an overview over its structure click here ; and its activities click here .

Geomagnetic Coordinate Systems: for an overview click here .

We are now going to use OpenDX to examine the configuration of the magnetosphere by visualizing results from the LFM for three different directions of the interplanetary magnetic field (IMF) in a solar wind with constant parameters. The network we have created will allow you place Cut Planes at various locations within the magnetosphere. On these cut planes you can place a variety of scalar parameters, e.g. Density, Vx, J.E, etc. In addition to the cut planes we have provided an interface which will allow to select points from which magnetic field lines can be traced throughout the computational domain.

Loading the network

To start Lab04 with CISM_DX extensions, click here ; this will cause a Visual Program Editor window to open.

Once the new network is loaded we need to open the Main Control Panel. In OpenDX, control panels are used to allow for user interaction with a network. You can design a network so that the user does not need to interact with the VPE. Instead, the user modifies parameters in a control panel and manipulates an image with the mouse.

Main Control Panel

In the top menu bar, select Windows, Open Control Panel by Name, and then Main Control Panel. The Main Control Panel contains several dialog boxes which we will use to investigate the structure of the magnetosphere.

Here is a summary of the dialog boxes and their functionality.

• HDF Data Filename: This dialog box allows you choose the data file from which data is imported. The button on the right with the three dots will bring up a File Selector which you can use to choose between files with data under three IMF directions.
• Cut Plane: This dialog box allows you to choose between three different cut plane directions, e.g., XY, XZ, and YZ.
• CutPlane Scalar: In this dialog box you can chose the scalar parameter to be plotted on the Cut Plane. In addition to the MHD parameters, e.g. Density, Vx, Bx, etc., you can also plot the magnitudes of the vectors and the dot products J.B and J.E.
• CutPlane Location: Here you can set the value for constant direction of the cut plane.
• CutPlane Transparency: In this dialog box you can set the transparency of the Cut Plane. A transparency of 1 makes the cut plane a solid object. A value around 0.8 will allow you to see through the cut plane which can be very helpful in examining field lines.
• Vector: In the final dialog box you can choose the Vector quantity used to drive the field line tracing. In this lab we will leave this set on B, but after the lab is complete you are welcome to try tracing field lines for other vector parameters.

This network allows you to set the starting location for a set of magnetic field lines. In order to understand this process, we need to execute the network once with CTRL-E. Once you have the image window visible go ahead and bring up the View Control Panel by typing CTRL-V when the image window is in focus or by selecting Options, View Control from the image menu bar. In the Mode dialog box choose Pick. At the bottom of the View Control Panel you will see a Pick(s) scroll list with Red Field Lines visible.

Use the mouse to select three points inside the magnetosphere as origins for field lines and then Execute the network. It's important to point out here that the Pick module is designed to set the points on the Cut Plane that you can see in the Image Window. After these field lines are visible in the Image window change the Pick(s) scroll list to White Field Lines and choose a few points outside the magnetosphere as points for new field lines which will appear after you Execute the network. NB: In order for both colors of field lines to appear in the Image window at the same time, you must first set the locations the Red Field Lines and then Execute network. After red field lines are visible, you can then create the White Field Lines.

Southward IMF

Lets begin by examining how the magnetosphere is structured during southward IMF. The HDF Data File should be already set to "south-imf.hdf". Get a XY Cut Plane of |J| at z = 0 and set the View to Front Now use Pick to set some Red Field Lines on the inside of current peak and Execute. Once those field lines are visible set some White Field Lines on the outside current peak and Execute. Go ahead and Rotate the view and what do you notice about these field lines? Try looking for the magnetopause in some of the other scalars, e.g. Density, Ey, and |B|. Pay close attention to the |B| plot in a Front View.

Test your knowledge:

• What do you think the dark line near the magnetopause boundary is?

Now Get a XY Cut Plane of |J| at z = 5 and set the View to Front Now use Pick to set some Red Field Lines on the inside of current peak and Execute. Once those field lines are visible set some White Field Lines on the outside current peak and Execute. Go ahead and Rotate the view. What do you notice about these field lines? How do these field lines differ from those you choose at the z=0 plane?

Northward IMF

Now lets look at the structure for northward IMF. Set the HDF Data File to north-imf.hdf. Get a XY Cut Plane of |J| at z = 5 and set the View to Front from th View Control panel . Use Pick to set some Red Field Lines on the inside of location of peak current and then Execute. Once those field lines are visible, set some White Field Lines on the outside current peak and Execute. How are these field lines different from those you looked at for Southward IMF? Now get a YZ Cut Plane of |J| at X =2 and set the View to Right. The +z direction with be pointing left. You can use the 2d rotation mode (right mouse button) to get the z direction up. Now use Pick to set some Red Field Lines at the maximum of the upper current peak and Execute. Once those field lines are visible set some White Field Lines at the maximum of the lower current peak and Execute. Go ahead and Rotate the view. How are these field lines connected to solar wind?

Test your knowledge:

• Is the magnetosphere closed for Northward IMF?

Westward IMF

Now lets look at the structure for westward IMF. Set the HDF Data File to west-imf.hdf Get a XY Cut Plane of |J| at z = 0 and set the View to Front Now use Pick to set some Red Field Lines on the inside of the current sheet and Execute. Once those field lines are visible set some White Field Lines on the outside current sheet and Execute. Go ahead and Rotate the view and what do you notice about these field lines? Now get a YZ Cut Plane of |J| at x = 5 and set the View to Right. The +z direction with be pointing left. You can use the 2d rotation mode (right mouse button) to get the z direction up. Now use Pick to set some Red Field Lines on the inside of the upper current sheet and Execute. Once those field lines are visible set some White Field Lines on the inside of lower current sheet and Execute. Go ahead and Rotate the view and what do you notice about these field lines? Return to the Right View and see if you can find the reconnection location by setting the Red Field Lines inside the upper current sheet and a matching set of White Field Lines on the outside of the current sheet.