Student interpretations of space science imagery and

visualizations: 2-D vs. 3-D images of the substorm current wedge

Ramon Lopez, Niescja Turner, and Kastro Hamed Dept. of Physics

University of Texas at El Paso

Conclusions• 2-D drawings of 3-D systems, even with several

minutes of explanations, can still leave students with misconceptions

• Spatial rotation of mental images [e.g. Kosslyn et al., 1995] is a issue when novices are trying to determine the implications of 3-D current systems

• All magnetic field/electric current systems are inherently 3-D, so the apparent inability many students have in applying concepts in such setting may stem from difficulties in visualizing and manipulating visual images, rather than basic difficulties with concepts like the “right-hand rule”

The substorm current wedge

• The Substorm Current Wedge is a current system that forms in Earth’s magnetotail during periods of magnetic activity called substorms

• A portion of the cross tail current that flows across the center of the magnetopshere is diverted into the ionosphere along the magnetic field, where it flows horizontally (to the ground), then returns along the magnetic field to the magnetotail

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Vpython

• Open-source package (www.vpython.org) that runs on top of python - available for many platforms

• Can produce wide range of 3-D diagrams that can be displayed in perspective, using color stereo separation, or be used in a GeoWall

• Objects can be rotated and you can zoom in and out.

• We used Vpython to create renderings of the substorm current wedge

Students

• All students have had some experience with space physics and the magnetosphere

• One student (#6) has had significant exposure to the magnetosphere and its current systems, including the substorm current wedge

• None of the students has done research involving substorms

Students• Student 1 - Senior physics major. Has done space science

research for 2 years.• Student 2 - Junior physics major. Has done space science

research for 6 months.• Student 3 - Junior physics major. Has done space science

research for 1 year.• Student 4 - Junior physics major. Has done space science

research for 18 months.• Student 5 - Sophomore physics major. Has done space science

research for 1 year. • Student 6 - Grad student. Has done space science research for

2.5 years• Student 7 - Sophomore physics major. Has done space science

research for 9 months.• Student 8 - Junior physics major. Has done astronomy research

for 1 year.

Methodology 1• Students were asked to describe how one can determine

the direction of a magnetic field produced by a current• Students were then presented with the standard 2-D

rendering of substorm current wedge used in “Introduction to Space Physics” by Kivelson and Russell [1995] and given an explanation of the diagram

• Students were interviewed about the diagram and asked to determine the magnetic perturbations in the north-south and east-west component of the magnetic field at an observation point inside the wedge, to the east of the center, in the northern hemisphere

Methodology 2• Students were then presented with a stereo rendering of the current

wedge (a Vpython image using red-cyan color separation) on a laptop [see below for perspective rendered current wedge]

• Students were interviewed about the image and asked to determine the magnetic perturbations in the north-south and east-west component of the magnetic field at an observation point inside the wedge, to the east of the center, in the northern hemisphere.

• Students were also asked to compare and contrast the two images• One student was given the 3-D image before seeing the 2-D image to

control for the “seeing it again” effect• All interviews were videotaped and analyzed to determine conclusions

Findings• All students correctly described and demonstrated the “right-

hand rule”• All students had great difficulty determining the magnetic

perturbations from the 2-D drawing - none got them all correct - even in cases where the student was clear on the basic structure of the wedge

• All students were able to determine all the magnetic perturbations from the 3-D rendering of substorm current wedge

• Three students developed incorrect ideas about the circulation of the currents from the 2-D drawing, but revised their pictures after seeing the 3-D image

• One student was shown the 3-D drawing without benefit of the 2-D drawing - he got the magnetic perturbations without much difficulty. Student success is not a “see it a second time” issue.

FindingsTable 2 – Interview results

Student Right-Hand-Rule

δB from2- D SCW

δB from3- D SCW

Misinterpretationof 2- D drawing

Im agerotationiss (ue explic )it

1 yes no yes no no2 yes no yes yes no3 yes no yes yes yes4 yes no yes no no5 yes N/A yes N/A yes6 yes no yes no yes7 yes no yes yes yes8 yes no yes no no

Student Comments: 2D v.s 3D• Student 7 - I am used to seeing these [2-D images] in

textbooks all the time, but they don’t help and I can’t actually describe to you why they don’t help. But those [pointing to the 3-D rendering] help a lot more.

• Interviewer - …So you thought that this current came out of the north and down into the south? [incorrect]

• Student 7 - [student nods yes] And there was a complete loss of current in the wedge…and [referring to the correct explanation] you did tell me that, but I couldn’t see it after you told me.

Student Comments: Mental rotations - Too much cognitive load?

• Interviewer: When you first started describing all of this…you gave a very good description of the substorm current wedge and did not have much problem in understanding how that produced the positive H component, but you were struggling with the East-West. But when you saw this [pointed to the 3D computer animation] something changed. What can you say about that?

• Student 6 - I guess being able to not focus so much on seeing it 3D and more focus on what the current is going to produce—frees up some brain width… In the 2 dimensional image you have to figure out what is this like in 3D. The image in the book is from one perspective. You have to also rotate it…around and figure things out.

Student Comments: cont.• Interviewer: When you looked at it in 3D, how did it match what

you were thinking when you were looking at the 2D picture in the book?

• Student 6: The current, it matched very well. It is very much what I expected. But being able to rotate the image in the simulation and not having to do it in my mind…you can look at the picture and say what is going to happen from this picture, whereas in the book you have to keep that in mind then from that figure out the effect.

• Interviewer: So, you were having some difficulty with envisioning it in 3D and rotating it in your mind?

• Student 6: Yes, having to switch back and forth between what it looks like and what is it going to do. It takes a lot more effort than if you can just focus on what is it going to do and the effects it is going to have. Whereas in 3D image, you can set up the situation you want and then ask what is it going to do. So, it is one thing to think about at the time.

Student Comments: Incorrect rotation at the root of 2-D misinterpretation

• Interviewer: What about the southern hemisphere in this figure?

• Student 3: Well, you can’t see it. I can flip it in my mind, but it was different in the simulation [3-D rendering] because I didn’t think about…I flipped it all the way over so I thought that the bottom current here was coming out this direction on this side [pointing to the diagram and indicating the incorrect direction]…like, I turned these currents in the opposite direction.

Conclusions• 2-D drawings of 3-D systems, even with several

minutes of explanations, can still leave students with misconceptions

• Spatial rotation of mental images [e.g. Kosslyn et al., 1995] is a issue when novices are trying to determine the implications of 3-D current systems

• All magnetic field/electric current systems are inherently 3-D, so the apparent inability many students have in applying concepts in such setting may stem from difficulties in visualizing and manipulating visual images, rather than basic difficulties with concepts like the “right-hand rule”