7,161 research outputs found
Electrodynamic effects of Jupiter's satellite Io
Electrodynamic effects of Jupiters satellite I
An investigation of Fe XVI emission lines in solar and stellar EUV and soft X-ray spectra
New fully relativistic calculations of radiative rates and electron impact
excitation cross sections for Fe XVI are used to determine theoretical
emission-line ratios applicable to the 251 - 361 A and 32 - 77 A portions of
the extreme-ultraviolet (EUV) and soft X-ray spectral regions, respectively. A
comparison of the EUV results with observations from the Solar
Extreme-Ultraviolet Research Telescope and Spectrograph (SERTS) reveals
excellent agreement between theory and experiment. However, for emission lines
in the 32 - 49 A portion of the soft X-ray spectral region, there are large
discrepancies between theory and measurement for both a solar flare spectrum
obtained with the X-Ray Spectrometer/Spectrograph Telescope (XSST) and
observations of Capella from the Low Energy Transmission Grating Spectrometer
(LETGS) on the Chandra X-ray Observatory. These are probably due to blending in
the solar flare and Capella data from both first order lines and from shorter
wavelength transitions detected in second and third order. By contrast, there
is very good agreement between our theoretical results and the XSST and LETGS
observations in the 50 - 77 A wavelength range, contrary to previous results.
In particular, there is no evidence that the Fe XVI emission from the XSST
flare arises from plasma at a much higher temperature than that expected for Fe
XVI in ionization equilibrium, as suggested by earlier work.Comment: 6 pages, 4 tables, 1 figure, MNRAS in pres
Spacelab data analysis and interactive control study
The study consisted of two main tasks, a series of interviews of Spacelab users and a survey of data processing and display equipment. Findings from the user interviews on questions of interactive control, downlink data formats, and Spacelab computer software development are presented. Equipment for quick look processing and display of scientific data in the Spacelab Payload Operations Control Center (POCC) was surveyed. Results of this survey effort are discussed in detail, along with recommendations for NASA development of several specific display systems which meet common requirements of many Spacelab experiments
Coronal Electron Confinement by Double Layers
In observations of flare-heated electrons in the solar corona, a longstanding
problem is the unexplained prolonged lifetime of the electrons compared to
their transit time across the source. This suggests confinement. Recent
particle-in-cell (PIC) simulations, which explored the transport of
pre-accelerated hot electrons through ambient cold plasma, showed that the
formation of a highly localized electrostatic potential drop, in the form of a
double layer (DL), significantly inhibited the transport of hot electrons (T.C.
Li, J.F. Drake, and M. Swisdak, 2012, ApJ, 757, 20). The effectiveness of
confinement by a DL is linked to the strength of the DL as defined by its
potential drop. In this work, we investigate the scaling of the DL strength
with the hot electron temperature by PIC simulations, and find a linear
scaling. We demonstrate that the strength is limited by the formation of
parallel shocks. Based on this, we analytically determine the maximum DL
strength, and find also a linear scaling with the hot electron temperature. The
DL strength obtained from the analytic calculation is comparable to that from
the simulations. At the maximum strength, the DL is capable of confining a
significant fraction of hot electrons in the source
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