[This paper is part of the Focused Collection on Gender in Physics.] We have investigated gender differences in performance over the past eight years on the Australian Science Olympiad Exam (ASOE) for physics, which is taken by nearly 1000 high school students each year. The ASOE, run by Australian Science Innovations (ASI), is the initial stage of the process of selection of teams to represent Australia at the Asian and International Physics Olympiads. Students taking the exam are generally in their penultimate year of school and selected by teachers as being high performing in physics. Together with the overall differences in facility, we have investigated how the content and presentation of multiple-choice questions (MCQs) affects the particular answers selected by male and female students. Differences in the patterns of responses by male and female students indicate that males and females might be modeling situations in different ways. Some strong patterns were found in the gender gaps when the questions were categorized in five broad dimensions: content, process required, difficulty, presentation, and context. Almost all questions saw male students performing better, although gender differences were relatively small for questions with a more abstract context. Male students performed significantly better on most questions with a concrete context, although notable exceptions were found, including two such questions where female students performed better. Other categories that showed consistently large gaps favoring male students include questions with projectile motion and other two-dimensional motion or forces content, and processes involving interpreting diagrams. Our results have important implications, suggesting that we should be able to reduce the gender gaps in performance on MCQ tests by changing the way information is presented and setting questions in contexts that are less likely to favor males over females. This is important as MCQ tests are frequently used as diagnostic tests and aptitude tests as well as to assess learning. DOI: 10.1103/PhysRevPhysEducRes.12.020111 I. MOTIVATIONEach September, nearly 1000 Australian high school students take the Australian Science Olympiad Exam (ASOE) for physics. On the basis of performance in the ASOE, approximately 24 students are chosen to attend a summer school "training camp" in January of the following year. The top eight students from the summer school make up the Australian team for the Asian Physics Olympiad (APhO) in April of that year, and five of these students go on to attend the International Physics Olympiad (IPhO) in July. The ASOE is the thus the first hurdle in an intensive selection and training process.The students who take the ASOE are selected by their teachers as being of high ability in physics, and are mainly in year 11 (the penultimate year of high school) and about 16 years old. Typically between a quarter and a third of these students are female, which is approximately the same fraction as the total year 11 physics cohort. How...

Lower hybrid (LH) waves can interact resonantly with both electrons and ions transferring energy between the species. For this reason the properties of LH waves are of interest. Most treatments of LH waves include either electromagnetic (EM) or warm plasma effects but not both. Here a new analytic dispersion relation for LH waves, including both EM and warm plasma effects, is derived and shown to be more consistent than the previous analytic dispersion relations with numerical results. These comparisons show a very good agreement of the real part of the frequency and reasonable agreement of the imaginary part for a wide range of parameters. It is found that ion magnetization effects, which have been neglected in all previous analytic treatments of LH waves, are surprisingly important. When ion magnetization effects become important the continuous LH mode breaks up into a series of segments of ion Bernstein modes.

Abstract. Most treatments of lower hybrid waves include either electromagnetic or warmplasma effects, but not both. Here we compare numerical dispersion curves for lower hybrid waves with a new analytic dispersion relation that includes both warm and electromagnetic effects. Very good agreement is obtained over significant ranges in wavenumber and plasma parameters, except where ion magnetization effects become important.

The resistive instabilities and dispersion of obliquely propagating waves near the lower hybrid (LH) frequency are studied in plasma carrying a current parallel to the magnetic field. Possible applications of these instabilities include magnetic reconnection regions where LH-like waves may accelerate and heat both ions and electrons. A resistive instability is found in one of the four LH-like wave modes for electron drift speeds several times greater than the electron thermal speed for representative parameters. Numerical fully electromagnetic kinetic calculations of the solutions to the linear dispersion equation are compared with more approximate analytic calculations and show good agreement. The analytic results indicate that ion magnetization effects play a critical role in the resistive instability.

The dispersion and reactive instabilities of obliquely propagating waves near the lower hybrid (LH) frequency are studied in plasma carrying a current parallel to the magnetic field. Possible applications of these instabilities include magnetic reconnection regions, where LH-like waves may accelerate and heat both ions and electrons. In plasmas with a bulk drift of electrons relative to the ions at speed vd along the magnetic field, the forward and backward propagating LH modes are shown to be replaced by four LH-like modes. Reactive instabilities are discovered here for a forward propagating mode with Re(ω)≈k∥vd/2 and a backward propagating mode with Re(ω) <~5Ωi. Numerical warm, fully electromagnetic, kinetic calculations are compared with cold plasma calculations and agree well, confirming that the discovered instabilities are reactive. In the cold plasma limit, the forward and backward propagating instabilities occur for vd below and above some thresholds, respectively.