We present the general properties of the far-ultraviolet (FUV; 1370-1710 Å) continuum background over most of the sky, obtained with the Spectroscopy of Plasma Evolution from Astrophysical Radiation instrument (SPEAR, also known as FIMS), flown aboard the STSAT-1 satellite mission. We find that the diffuse FUV continuum intensity is well correlated with N HI , 100 µm, and Hα intensities but anti-correlated with soft X-ray intensity. The correlation of the diffuse background with the direct stellar flux is weaker than the correlation with other parameters. The continuum spectra are relatively flat. However, a weak softening of the FUV spectra toward some sight lines, mostly at high Galactic latitudes, is found not only in direct-stellar but also in diffuse background spectra. The diffuse background is relatively softer than the direct stellar spectrum. We also find that the diffuse FUV background averaged over the sky has a bit softer spectrum compared to direct stellar radiation. A map of the ratio of 1370-1520 Å to 1560-1710 Å band intensity shows that the sky is divided into roughly two parts. However, this map shows a lot of patchy structures on small scales. The spatial variation of the hardness ratio seems to be largely determined by the longitudinal distribution of OB-type stars in the Galactic plane. A correlation of the hardness ratio with the FUV intensity at high intensities is found but an anti-correlation at low intensities. We also find evidence that the FUV intensity distribution is log-normal in nature.

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[1] Substorms sometimes occur repetitively with a period of $1-4 hours. In this paper we examine repetitive substorms, identified using particle injections and positive H bays on the nightside, that we find to occur during corotating high-speed streams associated with coronal holes. The high-speed streams often last for several days and are accompanied by large amplitude Alfvén waves of the interplanetary magnetic field (IMF). We find that repetitive substorms occur every $1-4 hours, regardless of the solar cycle phase, whenever the Earth's magnetosphere is impinged by these high-speed streams. We further find that a significant number of these substorms are associated with repetitive northward turnings of the Alfvénic IMF, each northward turning preceded by weakly-to-moderately southward IMF, i.e., B z $ À3.6 nT for $29 min on the average. We present eight example intervals where most of the repetitive substorms were associated with a northward turning. Statistically, for 63.5% of 312 substorms we are able to identify a reasonable association with a northward turning. While limitations of the Weimer-mapped IMF used here and the spatial structure of the Alfvénic IMF prevent us from estimating a precise figure for the percentage of IMF triggered substorms, our results indicate that many of the repetitive substorms are likely due to repetitive triggering by the Alfvénic IMF.

Although many methods of detecting extra-solar planets have been proposed and successful implementation of some of these methods enabled a rapidly increasing number of exoplanet detections, little has been discussed about the method of detecting satellites around exoplanets. In this paper, we test the feasibility of detecting satellites of exoplanets via microlensing. For this purpose, we investigate the effect of satellites in the magnification pattern near the region of the planet-induced perturbations by performing realistic simulations of Galactic bulge microlensing events. From this investigation, we find that although satellites can often cause alterations of magnification patterns, detecting satellite signals in lensing light curves will be very difficult because the signals are seriously smeared out by the severe finite source effect even for events involved with source stars with small angular radii.