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An Interdisciplinary Undergraduate Space Course

Understanding The Process of &ience Through One Field's Colorful History

Ramon E. Lopez

cience education in this country ence education have in general lagged vCtudents need to be aware is in its greatest period of fer- in implementing this philosophy. ment since the post-Sputnik However, many of the ideas solidly in that science h a human frenzy a generation ago. In that earlier the mainstream of precollege science time, however, educators' emphasis education reform (such as a creation. Although the was on producing more and constructivist, interdisciplinary ap- methods and ethics of engineers. Today we recognize that all proach) are now being advocated for Americans need a good science back- college science teaching (e.g., McIn- science mean that, in the ground. tosh, 1994, Redish, 1994). I believe The ability to observe, measure, that such ideas hold considerable long run, the truth will think quantitatively, and reach logical promise, that nontraditional courses win out, one cannot conclusions based on available evi- informed by advances in precollege dence is a set of skills that everyone education should be developed, and underestimate the power entering the workforce needs to ac- that information about such courses be quire if our country is to be competi- disseminated to a wider audience. of personalities when tive in a global economy. Moreover, as In order to develop this idea more considering how science public policy increasingly crystallizes fully, I proposed to teach a historically around scientific issues, it is critical based course about space physics as an is created. that citizens be educated in science so honors course at the University of that they may provide informed debate Maryland--College Park (UMCP). and consent on these issues. The honors program at UMCP was es- These issues are major driving fac- tablished to foster broad-based under- tors in the systemic reform of graduate courses that utilize in_,,vative precollege science education, which is teaching techniques to provide exem- seen the essential tool for not only de- veloping science content knowledge, Ramon E. Lopez isan associate re- but also "scientific habits of mind" search in the department of (Benchmarks for Science Literacy, astronomy, University of Maryland, 1994) Undergraduate and graduate sci- College Park, MD 20742.

February 1996 JCST 263 platy education to a select group of basic physics, especially those aspects upper atmosphere, where auro- students. Classes are small (no more that play a role in the near- space rae are commonly visible; the than 20 students) and draw from a di- environment. acts as the "television screen" for verse student population. Although processes occurring in space ul- space physics generally is presented in A CONTEXTUALOVERVIEW timately powered by the . advanced courses emphasizing on Space is not empty. It is filled with The sun produces a continuous out- plasma physics, I designed an intro- ionized gases, called plasmas, and elec- flow of plasma, known as the solar ductory course that would have four tromagnetic fields. Most of the visible , that fills interplanetary space. basic goals: universe is in the plasma state, al- When this plasma strikes Earth's ,nag- • To acquaint students with geomag- though on Earth we are more familiar netic field, a comet-shaped cavity netic and auroral phenomena and their with the other three states of matter-- called the is formed in the . The magnetosphere relationship to the space environment; solids, liquids and gases. In our envi- • To examine issues related to the his- ronment, plasmas are encountered boundary is located where the internal tory of science using the evolution of only in natural electrical discharges (mostly magnetic) and external (mostly one field as an example; such as lightning, in man-made objects plasma) pressures balance. On the day- • To develop familiarity with basic such as the plasmaspheres so prevalent side, the Earth's is com- skills such as describing and interpret- at novelty gift shops, or in devices at pressed and blunted into a bullet-head ing observations, analyzing scientific research centers in which experiments shape by the force of the solar wind papers, and communicating the results in controlled nuclear fusion are con- flow. On the nightside, the Earth's of their own research; and ducted. The most spectacular encoun- magnetic field is drawn out into a long • To provide some understanding of ter with natural plasmas is found in the magnetotail extending several hundred

Figure 1. A cutaway view of the magnetosphere, the comet-shaped region of space controlled by the Earth's magnetic field. Also indicated in the figure are several of the major regions and currents that comprise the magnetosphere. The Van Allen radiation belts, which are not labeled in this figure, generally lie within the .

Solar wind

264 JCST February 1996 earthradiiantisunward.Bycompari- Gauss, Edward Sabine and Richard among them studies of geomagnetic son, the moon orbits at 60 earth ra- Carrington, it was known that "mag- storms and a theory of the . dii. Figure 1 depicts a schematic netic storms" were a global phenom- He was a prolific writer and very per- model of the earth'k magnetosphere, enon (if a poorly understood one) and sonable, as well as being a brilliant sci- which itself contains many internal that they were in some way connected entist; in due course he came to domi- SEFLICtLIFCS. to the sun and solar activity (see nate the field. Chapman's and Large-scale plasma physics generally Chapman and Bartels, 1940, Chapter Birkeland's approaches to physics were employs the language of magnetohy- 26). very different, and Chapman did not d rodynamics--hydrodynamics in , a Norwegian accept much of anything that which the fluid is electrically conduct- physicist who studied under Henri Birkeland did (possible reasons for this ing. This is why we speak of balanc- Poincard, took up the study of geo- are discussed by Dessler, 1984). He felt ing magnetic and plasma pressure at magnetic perturbations and the aurora that Birkeland had misinterpreted his the magnetosphere's boundary. The at the turn of the century. Birkeland observations and he put no credence in balance is created through enormous was a fascinating character who raised Birkeland's concept of field-aligned elecuical currents that deform and money from a variety of sources to fi- currents. Because of Chapman's influ- confine the Earth's magnetic field to nance polar expeditions and establish ence, the scientific consensus was that the comet-like shape called the mag- magnetic observatories (Egeland, the currents associated with Birkeland's netosphere. These currents total be- 1984). Using data from these and disturbances were completely con- tween one and five million amperes. other magnetic observatories around tained in the ionosphere (Figure 3). Some of the currents flow down along the world, he came to the conclusion This was the state of affairs when the Earth's magnetic field into the po- that the electric currents during geo- Hannes Alfven entered the field. lar regions. If the currents are strong magnetic disturbances were "... driven Alfven's approach to physics was much enough, processes that are still not by a supply of electricity from with- like Birkeland's--intuitive and heavily completely understood create accelera- out." Birkeland envisioned solar elec- influenced by laboratory experiments. tion regions that energize upward- trons coming in streams from the sun, He felt that many of Birkeland's ideas, moving ions and downward-moving flowing down along the Earth's mag- such as the existence of field-aligned electrons. The accelerated electrons netic field, driving spatially-localized currents, were correct, though he strike the upper atmosphere and cause horizontal currents a couple of hun- agreed with Chapman that clouds of a glow like that in a neon tube, which dred kilometers above the Earth's sur- lionized gas, or plasma, emitted from is called the aurora. face, then flowing back out (see Fig- the sun would have to have equal The electrical energy that drives the ure 2). numbers of positive and negative currents comes from the flow of the Birkeland's ideas encountered some charges, unlike Birkeland's electron solar wind past the Earth's magnetic skepticism, and there were some prob- streams. Throughout his most of his field, which creates a cosmic dynamo. lems with his scenario. Critics pointed career he had to battle against The total current that is driven de- out that beams of electrons would dis- Chapman, the outstanding senior sci- pen& on how much solar-wind en- perse due to self-repulsion of like entist of the time. As a result Alfven ergy is coupled to the magnetosphere, charges, and that if the Sun emitted was forced to publish primarily in ob- which in turn is dependent on how negative charges it would itself become scure Swedish journals. In 1950 he much interconnection there is be- positively charged. These objections published Cosmical Electrodynamics, tween the interplanetary magnetic did not sway Birkeland, who was con- which was his attempt to reach (and field and the magnetospheric field. vinced that auroral magnetic distur- convince) a wider audience. However, When that energy input is especially bances were driven by current systems most of Alfven's ideas were not quickly large, the result is a disturbance in the that connected to space through a accepted by the community, and even Earth's magnetic field called a geo- magnetic fleld-aligned component. In those that in time were accepted were magnetic storm. the last few years of his life his health often not attributed to him (Dessler, The first person to report such geo- and the quality of his work suffered, 1970). Nevertheless, recognition of his magnetic disturbances was a well- perhaps as a result of mercury poison- contributions finally came in 1970 known London instrument maker and ing (Dessler, 1984). Birkeland died in when he was awarded the Royal Society Fellow, George Graham 1917 in trying to make his way in physics. (Graham, 1724). Shortly thereafter, it back to from Egypt the long When manmade satellites began to was noted that such disturbances were way via the Far East because of the orbit the Earth, a wealth of new phe- attended by auroral displays of un- war. nomena were discovered. The first usual activity and brilliance (Celsius, The next great figure in geomag- great discovery was the radiation belts, 1740). By the late 19th century, netism was Sidney Chapman, who en- named after their discoverer, James thanks to the work of scientists like tered the field in 1918. Chapman Van Allen. The discovery of the solar Alexander Humbolt, Carl Friedrich played a pivotal role in several areas, wind, theoretically predicted by Gene

February 1996 JCST 265 Parkerin 1958,andof differentre- (1970) discussed, science occasionally something about science when making gionsof themagnetosphere,soonfol- undergoes "paradigm shifts," in which the decisions that all citizens must lowed.The"geography"of space be- the existing order of things is over- make. It may also be important to Mve gan to be mapped. turned or severely modified to account some understanding of how science is One of the more curious discover- for new observations that cannot be created. ies was the magnetic perturbations ob- contained within the existing pattern, served by polar orbiting spacecraft. thus creating a new paradigm. This COURSEDESIGN Originally interpreted as standing hy- process is by no means a smooth one, dromagnetic waves, it turned out that An essential element of good science and early doubters of the old paradigm education revolves around skills that they were the signature of Birkeland's risk being marginalized within the ex- are often referred to as "scientific pro- field-aligned currents (see Dessler, isting community, as was Alfven. cess skills." These include the abilit 3, to 1984). Within just a few years field- This kind of story is one worth tell- observe, analyze those observations, aligned currents, also called Birkeland ing, since students need to be aware come to logical and defendable conclu- currents, were accepted as real by the that science is a human creation. Al- sions based on the evidence, and to entire scientific community. Not only though the methods and ethics of sci- is existence of Birkeland currents now communicate one's findings clearly to ence mean that, in the long run, the others. These skills are fairly indepen- acknowledged as a matter of course, truth will win out, one cannot under- but they are now seen as critical trans- dent of any particular field of science, estimate the power of personalities though common to all science. As mitters of information and energy when considering how science is cre- pointed out above, I strongly believe fi'om one point of the magnetosphere ated. Unfortunately, science is too of- that another important (and often to another, providing a direct electri- ten presented as a precise progression, overlooked) aspect of science education cal connection between Earth's iono- and scientists are portrayed as infallible revolves around the process of science sphere and the space environment. priests of that mysterious discipline. as a human endeavor. Although space physics might seem Such perceptions are unhealthy in a to many to be a rather esoteric field The honors course "The Space En- democratic society because they lead to vironment and the Solar-Terrestrial with little broader import, this kind of unrealistic expectations on one hand, Connection" attempts to address both sudden shift in scientific consensus is and mistrust engendered by the un- issues by approaching a scientific sub- an excellent case study for the evolu- fathomable on the other. In the real tion of science as a whole. As Kuhn ject historically, retracing the steps of world, it may not be enough to know the scientists who made the discover-

Figure 2. Birkeland's original figure showing his proposed path of solar electrons along the polar magnetic field, and the resulting current system.

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266 JCST February 1996 &_i_ix_thc1_to\\-,".to;;.'..-'_'_-":....'N_..... nedc fiel.ds, they" xx'ete introduce8 to ies.Sixstudentsregisteredfor the Stewart (,1861) and his coixc\us\ons, course,whichwastaughtaspartofthe records, or and an essay comparing how they de- 1994SpringSemesteratUniversityof magnetograms, presented by Stewart scribed the observations with what (1861). That paper is the first publi- Maryland.Theyrepi'esentedasurpris- Balfour Stewart wrote. cation of geomagnetic field data using This approach continued when we inglydiversegroupof studentsgiven the then-new photorecordation tech- thesmalltotalnumber,rangingfrom examined the magnetograms collected niques. The students were divided into by Kristian Birkeland during his polar ajuniorEnglishmajorwhohadnever research groups of two, and each pair studiedcalculus,to afreshmanphys- expeditions. After we reviewed as a was asked to select one magnetogram icsmajorwhohadastrongfoundation class the observations, and discussed of the seven days' worth presented in inbasicphysicsandmathematics. some conclusions that could be drawn Stewart (1861). All groups chose Sep- The pedagogicalapproachis in- from them, the students read what tember 1, 1859, which was the most quiry-basedandconstructivist.In their Birkeland (1908) had to say and wrote magnetically disturbed day of the first assignment,the studentswere a report about his conclusions. We group. Their task was to examine the askedtowrite a short essay about what then proceeded to examine some of the observations, then write a joint de- they know about space, how they work of Sidney Chapman, using ex- know it, and what more they would scription of those observations. I then like to learn. Students also were asked to write a similar essay about electro- magnetism. In addition, the first class Figure 3. A comparison between Birkeland's current system and that advocated by Chapman (lrom Akasofu, 1984). Both are capable of explaining the major features of geomagnetic perturbations re- was used as a general discussion to ex- corded on the ground. However, polar-orbiting spacecraft will encounter transverse magnetic distur- amine the students' understanding of bances in Birkeland's picture, while they will not in Chapman's. concepts like "force" and "gravity." These essays, and the results of that first class, were used to develop a i primer on basic physics and electro- magnetism that occupied the first few weeks of the class, it turned out that the concepts of "force" and "gravity" were reasonably well understood; these concepts served as templates for devel- oping understanding about electric and magnetic fields, their sources, and the forces associated with them. In teaching this subject matter I tried to be Socratic as possible, and my EQUATORIAL VIEW POLAR VIEW method was much enhanced by the BIRKELAND'S CURRENT SYSTEM small number of students. By posing the right question it was often possible to elicit the response needed to move the discussion forward. Still, I had to rely some of the time on traditional didactic presentation. In addition, we conducted investigations both in and out of class using simple materials (magnets, pins, strings, batteries, bulbs, wires). The purpose of these experi- ments was to use simple observations of electromagnetic forces to determine the essential attributes of those forces (such as that the magnetic force on an electric current flowing in a wire is per- pendicular to the direction of the cur- rent and to the line between the mag- EQUATORIAL VIEW POLAR VIEW net and the current). CURRENT Once the students had some con- CHAPMAN'S SYSTEM __J cept of electric currents creating mag- February 1996 JCST 267

. ,. fT_Y_*'-" cerpts from Geomagnetism (1940). Stu- Moreover, I explained to my students dents were able to see from the data amined several cases of such events that that it is the duty of every scientist to were very familiar to the students from how Chapman defined a magnetic honestly render judgment (when storm, and both the similarities and the ground magnetometer perspective, asked) on their colleagues' papers, and dissimilarities with the events pre- but unfamiliar from the satellite point that on occasion I have felt forced to of view. This allowed them to see how sented by Birkeland. We also reviewed render harsh judgements on work important Birkeland currents are to what Chapman had to say about done by people I consider to be per- our current understanding, since they Birkeland's classification of geomag- sonal friends. It just so happens that netic disturbances--a classification are the basic agents of the connection sometimes, for a variety of reasons, sci- that Chapman rejected. between space and the ionosphere. ence can go awry, and the peer-review Following Chapman, we discussed The students also had to write a pa- process, being inherently conservative, per on Kuhn (1970), which accounted excerpts from H. Alfven's Cosmical reinforces the mistaken view until new Electrodynamics (1950), as well as some for 20 percent of their grades. In gen- evidence or insight can break down eral, the students showed a good un- of the reaction to Birkeland's and barriers. Alfven's ideas in the scientific literature derstanding of the points that Kuhn We continued to follow the story makes in his book. They were able to draw heavily on their understanding of the development of space physics to il- Science occasionally undergoes lustrate certain points. Although I have no control group to which to compare, )aradigrn shifts," in which the existing order I think that the students' understand- ing of Kuhn's thesis was much en- of things is overturned or severelymodified to account hanced by their experiential study of for new observations that cannot be contained within one relatively small paradigm shift--as one student put it, "I could really see the existingpattern. what he was talking about." I based my assessment of the stu- dents on a mixture of traditional and alternative means. In addition to the of the forties and fifties. By that point into the space age. We began with an various writing assignments in the my students could not contain them- examination of radiation data from selves. "Who was right?" they asked. course, students were assigned some Explorer III taken in 1958 and pre- traditional problems in vector algebra "Birkeland and Alfven, or Chapman?" sented by Van Allen (1983) in a his- I would have preferred not to tell them and basic physics (10 percent of the torical account of the early days of and let them discover the answer from grade). This could be scored in a tra- space exploration. Those data show a the space-age observations we were ditional manner. Still, much of the as- curious "dropout region" where the ra- soon to encounter. However, due to a sessment was performance-based, diation flux seemed to go to zero. An- succession of winter storms in early '94 which was much enhanced given the other figure, also presented by Van small number of students in the class. that closed the university several times Allen (1983), showed that in the labo- and cut our total class time, I felt A large part of the grade (40 percent) ratory the response of the Geiger tube forced to take a shortcut. I told them depended on how well they performed dropped to zero if the incoming radia- that the field-aligned currents deduced on in-class analysis of data and in the tion was too great. The students con- by Birkeland are real. discussions that followed. duded that the dropout region was ac- This precipitated a marvelous dis- The final exam incorporated mod- tually a region of very high radiation els of some aspects of how a scientific cussion about personalities, the where the Geiger tubes became satu- progress of science, and the essential community functions. A week before rated. This was the same conclusion class ended, students were divided into nature of peer-review. Students initially reached by Van Allen and his assis- two research groups, with a careful bal- felt that Chapman was a bad person tants, and they announced the discov- ancing of individual strengths. Each for rejecting Alfven's papers, and saw ery of the radiation belts that bear his group was given a package of data plots Alfven as some kind of tragic hero. But nalTle. I explained to them that Chapman was representing a geophysical event simi- This was followed by a general dis- lar to one that had been examined in actually a wonderful human being by cussion of magnetospheric structure. all accounts, whereas Alfven could be class. Without discussing with the Using their understanding of ground somewhat irascible and cantankerous. other group, each group prepared a magnetometer measurements, the stu- in rereading Chapman's criticism of small paper based on their data and re- dents were able to examine spacecraft Birkeland the students realized that it turned it to me on the last day of class. data and connect what happens in The papers constituted 40 percent of was measured, not mean-spirited. space to events on the ground. We ex- the final exam grade (the final being 30 268 JCST February 1996 percent of the course grade). tegrate data in a meaningful fashion, On final exam day, the students and to solve problems. Finally, they weie individually given a copy of the learned something about the space en- vironment. At the end of the final research papers from the other group. They then wrote reviews of that paper, exam, I reinforced that learning by re- which constituted 60 percent of the fi- turning their initial essays on what nal exam grade. Asking students to re- they know about space. By reading view anonymously the results of other those, they realized how far they had students' research proved to be an ex- come in understanding the electrical cellent summative assessment tool. In connection between sun and earth, my own career, I have noted that when and the vision of a universe filled with read a referees revkew of a paper cosmic p\asmas, magnetic £_e_.ds, and have submitted, I have a good idea of electric currents, o how well tile referee understands the subject matter. Sometimes the com- Acknowledgement I acknowledgewith thanks M. Rowe and W. Mohllngfor encourag- ments show tremendous insight, ing me to write this ardde,and A. Desslerfor helpful valuablecom- whereas other times it is clear that the men_son the manuscript.I am especiallyi,debted to my studentsfor the insightstheyhavegivenme. This work wassupportedby a Space referee doesn't have a clue. PhysicsEducation Outreach Supplement to NASA grant NAGW- 3222. Since the data presented to the stu- dent groups incorporated all of the References major topics we had discussed in class, AAAS. 1993. Benchmarks for Science Literacy. New the students were forced to rely on the York: Oxford University Press. broad range of core content and pro- Akasofu, S.-I. 1984. The magnetospheric currents: cess skills in both the writing of the An introduction. In T.A. Potemra, ed. Magneto- spheric Currents. 29-48. Washington, D.C.: Ameri- paper and the review. The review was can Geophysical Union. an especially powerful tool in this re- Alfven, H. 1950. Cosmical Electrodynamics. The In- gard, and the students' comments were ternational Series of Monographs on Physics 13. London: Oxford University Press. surprisingly sophisticated. In one re- Birkeland, K. 1908. The Norwegian Aurora Polaris view a student pointed out "...that they 1902-1903. Volume 1. Christiana, Norway: associate characteristics of a general Aschdong. Chapman, S., and J. Barrels. 1940. Geomagnetism. magnetic storm, such as the existence New York: Oxford University Press. of a , with a . A Celsius, A. 1740. Bermerkungen uber der substorm, as we now know, may or Magnemadel stundliche Veranderungen in ihrer Abweichung. Svensk. Vet. Acad. Handl. 296-299. may not include a ring current." That Dessler, A. J. 1970. Swedish Iconoclast Recognized student also commended the paper for after Many Years of Rejection and Obscurity. &i- some " ... keen observations..." ", and ence 170: 604-606. Dessler, A. J. 1984. The evolution of arguments re- concluded that as a scientific paper it garding the existence of field-aligned currents. In ... would not have been published but T.A. Potemra, ed. Magnetospheric Currents. 22-28. it's [sic] good work for college fresh- Washington, D.C.: American Geophysical Union. Tom Smith has two Egeland, A. 1984. Kristian Birkeland: The man and men." Another review pointed out that the scientist. In T.A. Potemra, ed. Magnetospheric different roles in life. a particular argument was made based Currents. 29-48. Washington, D.C.: American on the simultaneity of a particle flux Geophysical Union. Then again, Graham, G. 1724. Phil. Trans. R. Soc., London. increase at two different spacecraft, yet 383: 96. so does Clark Kent. the data show "...a time delay of 3 Kuhn, T. 1970. The Structure of Scientific Revolutions. minutes," and that on the basis of that McIntosh, W.J. 1994. Systemic Reform and the Col- Like Superman, when Tom's not in lege Science Educator, J. Coll. Sci. Teaching 23: the office, he performs humanitarian delay the argument may be invalid. 265-266. relief efforts and support roles vital Such careful attention to detail and Redish, Edward S, Implications of cognitive studies to our military. That's because Tom analytic approach will serve these stu- for teaching physics. Am. J. Phys. 62: 796-803. dents well in the future. Stewart, B. 1861. On the Great Magnetic Distur- represents the National Guard & bance which extended from August 28 to Septem- Reservewho now make up over half of To conclude, I feel that this course ber 7, 1859, as recorded by Photography at the our defense. Sowhen Tom asksyou for Kew Observatory. Phil. Trans. R. Soc. London. achieved what I envisaged. My stu- time off to serve,you can be a hero. 151 : 428-433. Give him the freedom to protect ours. dents learned some physics--enough, Van Allen, J. 1983. Origins of Magnetospheric Physics. at any :ate, to understand the course s Washington, D.C.: Smithsonian Institution Press. subject matter. They gained insight Van Heuvelen, A. 1991. Learning to think like a physicist: A review of research-based instructional into how science really works. They strategies. Am. J. Phys. 59: 891-897, 1991. displayed an ability to analyze and in-

February 1996 JCST 269