排序方式: 共有33条查询结果,搜索用时 31 毫秒
31.
H. A. Thronson T. G. Hawarden J. Bally S. J. Bell Burnell A. J. Penny D. Rapp 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1993,13(12):531-534
Radiative cooling of IR space telescopes is an alternative to embedding within massive cryostats and should offer advantages for future missions, including longer life, larger aperture for a fixed spacecraft size, lower cost due to less complex engineering, and easier ground handling. Relatively simple analyses of conventional designs show that it is possible to achieve telescope temperatures in the range of 25 to 40 K at distances from the sun of about 1 AU. Lower temperatures may be possible with “open” designs or distant orbits. At 25 K, an observatory will be limited by the celestial thermal background in the near- and mid-IR and by the confusion limit in the far-IR. We outline here our concept for a moderate aperture ( 1.75 m; Ariane 4 or Atlas launch) international space observatory for the next decade. 相似文献
32.
From solar nanoflares to stellar giant flares: Scaling laws and non-implications for coronal heating
Markus J. Aschwanden 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2007,39(12):1867-1875
In this study we explore physical scaling laws applied to solar nanoflares, microflares, and large flares, as well as to stellar giant flares. Solar flare phenomena exhibit a fractal volume scaling, V(L) L1.9, with L being the flare loop length scale, which explains the observed correlation between the total emission measure EMp and flare peak temperature Tp in both solar and stellar flares. However, the detected stellar flares have higher emission measures EMp than solar flares at the same flare peak temperature Tp, which can be explained by a higher electron density that is caused by shorter heating scale height ratios sH/L ≈ 0.04–0.1. Using these scaling laws we calculate the total radiated flare energies EX and thermal flare energies ET and find that the total counts C are a good proxy for both parameters. Comparing the energies of solar and stellar flares we find that even the smallest observed stellar flares exceed the largest solar flares, and thus their observed frequency distributions are hypothetically affected by an upper cutoff caused by the maximum active region size limit. The powerlaw slopes fitted near the upper cutoff can then not reliably be extrapolated to the microflare regime to evaluate their contribution to coronal heating. 相似文献
33.
Markus J. Aschwanden 《Space Science Reviews》2009,149(1-4):31-64
We transition from two-dimensional (2D) imaging observations of kink-mode loop oscillations in the solar corona to three-dimensional (3D) reconstructions by exploring two new methods: (1) De-projection of 2D loop tracings using the strategy of curvature radius maximization in 3D space, based on the assumption of force-free magnetic fields; and (2) stereoscopic triangulation of epipolar loop coordinates using coaligned images from the STEREO EUVI/A and B spacecraft. Both methods reveal new features of oscillating loops: non-circularity, non-planarity, and helical geometries. We extend the 3D reconstruction techniques into the time domain and find indications of circularly polarized (helical) kink-mode oscillations, in contrast to linearly polarized modes assumed previously. We discuss also hydrodynamic effects of coronal loops in non-equilibrium state that are essential for the detection and modeling of kink-mode oscillations. 相似文献