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1.
New values of hydrogen photoionization rates for subordinate continua arising from bound levels with the principal quantum number i = 2–5 have been evaluated numerically, using an extensive compilation of the observed photospheric radiation fields. These rates can be directly incorporated into the equations of statistical equilibrium as so-called fixed rates. We tabulate the photoionization rates and equivalent radiation temperatures for various heights above the photosphere, which is particularly useful for chromospheric and prominence non-LTE modeling. Finally, we compare our results with those previously obtained by other authors. 相似文献
2.
Phillips K.J.H. Read P.D. Gallagher P.T. Keenan F.P. Rudawy P. Rompolt B. Berlicki A. Buczylko A. Diego F. Barnsley R. Smartt R.N. Pasachoff J.M. Babcock B.A. 《Solar physics》2000,193(1-2):259-271
The Solar Eclipse Coronal Imaging System (SECIS) is an instrument designed to search for short-period modulations in the solar corona seen either during a total eclipse or with a coronagraph. The CCD cameras used in SECIS have the capability of imaging the corona at a rate of up to 70 frames a second, with the intensities in each pixel digitised in 12-bit levels. The data are captured and stored on a modified PC. With suitable optics it is thus possible to search for fast changes or short-period wave motions in the corona that will have important implications for the coronal heating mechanism. The equipment has been successfully tested using the Evans Solar Facility coronagraph at National Solar Observatory/Sacramento Peak and during the 11 August 1999 eclipse at a site in north-eastern Bulgaria. The instrument is described and preliminary results are outlined. 相似文献
3.
In this paper we present a new method of restoration of the true three-dimensional (3D) trajectories of prominence knots using
ground-based observations taken with a single telescope that is equipped with a Multi-Channel Subtractive Double Pass imaging
spectrograph. Our method allows us to evaluate the true 3D trajectories of the prominence knots without any assumptions concerning
the shape of the trajectories or the dynamics of the motion. The reconstructed trajectories of several knots observed in three
prominences are presented. 相似文献
4.
A quiescent prominence was observed in June 1997 by instruments onboard the SOHO spacecraft: the Solar Ultraviolet Measurements of Emitted Radiation (SUMER), Coronal Diagnostic Spectrometer (CDS) and Extreme-Ultraviolet Imaging Telescope (EIT), along with the coronagraph of the Wrocaw University Observatory at Bialków and the spectrograph of the Ondejov Observatory. We present prominence observations in higher lines of the hydrogen Lyman series (from L to L-9), together with some other UV lines obtained by SUMER. We extract the basic characteristics of the calibrated line profiles of these Lyman lines and compare them with the theoretical profiles computed from three kinds of NLTE models which also include prominence filamentation. Our principal result is that the current NLTE models are in principle capable of explaining the SUMER calibrated intensities in the observed Lyman lines. We also find that in order to fit all these lines, one has to consider a prominence-corona transition region (PCTR) with a temperature gradient. At low pressures, higher Lyman lines are still rather sensitive to the incident radiation which must be carefully taken into account in the modeling. From PCTR models, which also take into account the effect of ambipolar diffusion on the heating, we have derived the formation depths for the Lyman series lines. High Lyman lines seem to be formed just at the base of the PCTR. 相似文献
5.
D.R. Williams K.J.H. Phillips P. Rudawy M. Mathioudakis P.T. Gallagher E. O'Shea F.P. Keenan P. Read B. Rompolt 《Monthly notices of the Royal Astronomical Society》2001,326(2):428-436
The Solar Eclipse Corona Imaging System (SECIS) was used to record high-cadence observations of the solar corona during the total solar eclipse of 1999 August 11. During the 2 min 23.5 s of totality, 6364 images were recorded simultaneously in each of the two channels: a white light channel, and the Fe xiv (5303 Å) 'green line' channel ( T ∼2 MK) . Here we report initial results from the SECIS experiment, including the discovery of a 6-s intensity oscillation in an active region coronal loop. 相似文献
6.
We present the results of the analysis of thirteen events consisting of dm-spikes observed in Toruń between 15 March 2000
and 30 October 2001. The events were obtained with a very high time resolution (80 microseconds) radio spectrograph in the
1352 – 1490 MHz range. These data were complemented with observations from the radio spectrograph at Ondřejov in the 0.8 – 2.0 GHz
band. We evaluated the basic characteristics of the individual spikes (duration, spectral width, and frequency drifts), as
well as their groups and chains, the location of their emission sources, and the temporal correlations of the emissions with
various phases of the associated solar flares. We found that the mean duration and spectral width of the radio spikes are
equal to 0.036 s and 9.96 MHz, respectively. Distributions of the duration and spectral widths of the spikes have positive
skewness for all investigated events. Each spike shows positive or negative frequency drift. The mean negative and positive
drifts of the investigated spikes are equal to −776 MHz s−1 and 1608 MHz s−1, respectively. The emission sources of the dm-spikes are located mainly at disk center. We have noticed two kinds of chains,
with and without frequency drifts. The mean durations of the chains vary between 0.067 s and 0.509 s, while their spectral
widths vary between 7.2 MHz and 17.25 MHz. The mean duration of an individual spike observed in a chain was equal to 0.03 s.
While we found some agreement between the global characteristics of the groups of spikes recorded with the two instruments
located in Toruń and Ondřejov, we did not find any one-to-one relation between individual spikes. 相似文献
7.
We present an estimation of the lower limits of local magnetic field strengths in quiescent, activated, and active (surges) prominences, based on reconstructed three-dimensional (3D) trajectories of individual prominence knots. The 3D trajectories, velocities, tangential and centripetal accelerations of the knots were reconstructed using observational data collected with a single ground-based telescope equipped with a Multi-channel Subtractive Double Pass imaging spectrograph. Lower limits of magnetic fields channeling observed plasma flows were estimated under assumption of the equipartition principle. Assuming approximate electron densities of the plasma n e=5×1011?cm?3 in surges and n e=5×1010?cm?3 in quiescent/activated prominences, we found that the magnetic fields channeling two observed surges range from 16 to 40?Gauss, while in quiescent and activated prominences they were less than 10?Gauss. Our results are consistent with previous detections of weak local magnetic fields in the solar prominences. 相似文献
8.
Series of H spectra and slit-jaw H filtergrams of a quiescent prominence taken at Pic du Midi Observatory on 7 November 1977 are studied. The observations have been digitized by means of an automated Joyce Loebl microdensitometer. The image processing of the H filtergrams reveals an internal structure of the prominence consisting of several arches. Series of high-resolution H spectra obtained with the slit position located on a selected part of one of the prominence arches have been chosen for Doppler-shift analysis. The obtained time series of the line-of-sight velocity reveal large velocity variations near the periphery of the arch and a strong dependence of the velocity (in sign and magnitude) on the position along the slit. The prominence arch shows also cyclic displacements along the line-of-sight direction implying Alfvén string-mode oscillations. 相似文献
9.
10.
P. Rudawy K. J. H. Phillips A. Buczylko D. R. Williams F. P. Keenan 《Solar physics》2010,267(2):305-327
Some 8000 images obtained with the Solar Eclipse Coronal Imaging System (SECIS) fast-frame CCD camera instrument located at Lusaka, Zambia, during the total eclipse of 21 June 2001 have been analysed
to search for short-period oscillations in intensity that could be a signature of solar coronal heating mechanisms by MHD
wave dissipation. Images were taken in white-light and Fe xiv green-line (5303 ?) channels over 205 seconds (frame rate 39 s−1), approximately the length of eclipse totality at this location, with a pixel size of four arcseconds square. The data are
of considerably better quality than those that we obtained during the 11 August 1999 total eclipse (Rudawy et al.: Astron. Astrophys. 416, 1179, 2004), in that the images are much better exposed and enhancements in the drive system of the heliostat used gave a much improved
image stability. Classical Fourier and wavelet techniques have been used to analyse the emission at 29 518 locations, of which
10 714 had emission at reasonably high levels, searching for periodic fluctuations with periods in the range 0.1 – 17 seconds
(frequencies 0.06 – 10 Hz). While a number of possible periodicities were apparent in the wavelet analysis, none of the spatially
and time-limited periodicities in the local brightness curves was found to be physically important. This implies that the
pervasive Alfvén wave-like phenomena (Tomczyk et al.: Science
317, 1192, 2007) using polarimetric observations with the Coronal Multi-Channel Polarimeter (CoMP) instrument do not give rise to significant oscillatory intensity fluctuations. 相似文献