| Vol. 27, Issue 9 |
Solar active regions, which appear suddenly and can last for months, act as search lights by illuminating hydrogen atoms in interplanetary space. In 1996, the SOHO spacecraft recorded excesses of illumination on both the near and far sides of the Sun. Based on these observations, Bertaux et al. suggest a technique that could improve the quality of space weather forecasting. They propose that if the birth of a solar active region is first detected from space on the far side of the sun, it could help predict the impact of solar activity on the Earth's atmosphere and satellite systems before the active region emerges into Earth's view. . Dense, cold plasma flows out from the polar cap of the Jovian satellite Ganymede. Vasiliunas and Eviatar propose that the observed positive ions in the plasma of the polar magnetosphere of Ganymede are singly charged oxygen ions rather than protons as is commonly believed. In contrast to the problems posed by the proton assumption (such as there being no plausible mechanism for ionization of hydrogen at the rate required), the interpretation of the ions as O+ makes sense in terms of understanding the processes that shape Ganymede's neutral atmosphere and ionosphere, which consist almost entirely of oxygen in various forms. It is often difficult to determine whether magnetospheric processes are causally related or simply contemporaneous. Russell et al. examine the solar wind conditions and magnetospheric response surrounding the geomagnetic storm of September 24-25, 1998, to illustrate the conditions that result in auroral zone activity and in the build up of the ring current that lies embedded in the magnetosphere. They find that the flux of mechanical kinetic energy constitutes a large power source for the magnetosphere and show that the auroral electrojets and ring current are weakly correlated with each other. The process that creates the ring current thus depends on steady-state solar-wind coupling and not on substorms or on time-varying convective electric fields. |
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