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W. Curdt D. Germerott K. Wilhelm U. Schühle L. Teriaca D. Innes K. Bocchialini P. Lemaire 《Solar physics》2014,289(6):2345-2376
We have released an archive of all observational data of the VUV spectrometer Solar Ultraviolet Measurements of Emitted Radiation (SUMER) on SOHO that have been acquired until now. The operational phase started with ‘first light’ observations on 27 January 1996 and will end in 2014. Future data will be added to the archive when they become available. The archive consists of a set of raw data (Level 0) and a set of data that are processed and calibrated to the best knowledge we have today (Level 1). This communication describes step by step the data acquisition and processing that has been applied in an automated manner to build the archive. It summarizes the expertise and insights into the scientific use of SUMER spectra that has accumulated over the years. It also indicates possibilities for further enhancement of the data quality. With this article we intend to convey our own understanding of the instrument performance to the scientific community and to introduce the new, standard FITS-format database. 相似文献
2.
% High-resolution temporal observations performed with the SUMER spectrometer on SOHO provide an opportunity to investigate the electron density variations in the `quiet-Sun' solar transition region due to UV transient events. Two datasets obtained in the density sensitive lines belonging to the Oiv 1400 Å multiplet were searched for such events, leading to the identification of two explosive events, on 10 July 1996 and 31 May 1997. In both cases, the Oiv 1401.16/1404.81 density-sensitive line intensity ratio shows a clear variation, corresponding to enhancements in the electron density by factors of 3. This is fully consistent with recent 2.5D MHD simulations. The 10 July 1996 dataset also provided us with the opportunity to monitor the behavior of the electron density through an UV blinker. Despite an increase of a factor of two in the line intensities, no variation of the electron density was found. This suggests that the intensity enhancement is due to an increase in the filling factor. 相似文献
3.
Explosive events appear as broad non-Gaussian wings in the line profiles of small transition-region phenomena. Images from the Solar Dynamics Observatory (SDO) give a first view of the plasma dynamics at the sites of explosive events seen simultaneously in O?vi spectra of a region of quiet Sun, taken with the ultraviolet spectrometer Solar Ultraviolet Measurements of Emitted Radiation (SUMER) onboard the Solar and Heliospheric Observatory (SOHO). Distinct event bursts were seen either at the junction of supergranular network cells or near emerging flux. Three are described in the context of their surrounding transition region (304 Å) and coronal (171 Å) activity. One showed plasma ejections from an isolated pair of sites, with a time lag of 50 seconds between events. At the site where the later explosive event was seen, the extreme ultraviolet (EUV) images show a hot core surrounded by a small, expanding ring of chromospheric emission, which we interpret as a “splash.” The second explosive-event burst was related to flux cancellation, inferred from Helioseismic and Magnetic Imager (HMI) magnetograms, and a coronal dimming surrounded by a ring of bright EUV emission with explosive events at positions where the spectrometer slit crossed the bright ring. The third series of events occurred at the base of a slow, small coronal mass ejection (mini-CME). All events studied here imply jet-like flows probably triggered by magnetic reconnection at supergranular junctions. Events come from sites close to the footpoints of jets seen in Atmospheric Imaging Assembly (AIA) images, and possibly from the landing site of high-velocity flows. They are not caused by rapid rotation in spicules. 相似文献
4.
A. Vourlidas B. Sanchez Andrade-Nu?o E. Landi S. Patsourakos L. Teriaca U. Schühle C. M. Korendyke I. Nestoras 《Solar physics》2010,261(1):53-75
The Very high Angular resolution ULtraviolet Telescope (VAULT) is a sounding rocket payload built to study the crucial interface
between the solar chromosphere and the corona by observing the strongest line in the solar spectrum, the Ly α line at 1216 ?.
In two flights, VAULT succeeded in obtaining the first ever subarcsecond (
$0.5\hbox{$0.5\hbox{
) images of this region with high sensitivity and cadence. Detailed analyses of those observations contributed significantly
to new ideas about the nature of the transition region. Here, we present a broad overview of the Ly α atmosphere as revealed
by the VAULT observations and bring together past results and new analyses from the second VAULT flight to create a synthesis
of our current knowledge of the high-resolution Ly α Sun. We hope that this work will serve as a good reference for the design
of upcoming Ly α telescopes and observing plans. 相似文献
5.
We studied the evolution of a small eruptive flare (GOES class C1) from its onset phase using multi-wavelength observations
that sample the flare atmosphere from the chromosphere to the corona. The main instruments involved were the Coronal Diagnostic
Spectrometer (CDS) aboard SOHO and facilities at the Dunn Solar Tower of the National Solar Observatory/Sacramento Peak. Transition
Region and Coronal Explorer (TRACE) together with Ramaty High-Energy Spectroscopic Imager (RHESSI) also provided images and
spectra for this flare. Hα and TRACE images display two loop systems that outline the pre-reconnection and post-reconnection magnetic field lines and
their topological changes revealing that we are dealing with an eruptive confined flare. RHESSI data do not record any detectable
emission at energies ≥25 keV, and the observed count spectrum can be well fitted with a thermal plus a non-thermal model of
the photon spectrum. A non-thermal electron flux F ≈ 5 × 1010 erg cm−2 s−1 is determined. The reconstructed images show a very compact source whose peak emission moves along the photospheric magnetic
inversion line during the flare. This is probably related to the motion of the reconnection site, hinting at an arcade of
small loops that brightens successively. The analysis of the chromospheric spectra (Ca II K, He I D3 and Hγ, acquired with a four-second temporal cadence) shows the presence of a downward velocity (between 10 and 20 km s−1) in a small region intersected by the spectrograph slit. The region is included in an area that, at the time of the maximum
X-ray emission, shows upward motions at transition region (TR) and coronal levels. For the He I 58.4 and O v 62.97 lines, we determine a velocity of ≈−40 km s−1 while for the Fe XIX 59.22 line a velocity of ≈−80 km s−1 is determined with a two-component fitting. The observations are discussed in the framework of available hydrodynamic simulations
and they are consistent with the scenario outlined by Fisher (1989). No explosive evaporation is expected for a non-thermal
electron beam of the observed characteristics, and no gentle evaporation is allowed without upward chromospheric motion. It
is suggested that the energy of non-thermal electrons can be dissipated to heat the high-density plasma, where possibly the
reconnection occurs. The consequent conductive flux drives the evaporation process in a regime that we can call sub-explosive. 相似文献
6.
We studied the evolution of two small flares (GOES class C2 and C1) that developed in the same active region with different
morphological characteristics: one is extended and the other is compact. We analyzed the accuracy and the consistency of different
algorithms implemented in Reuven Ramaty High-Energy Spectroscopic Imager (RHESSI) software to reconstruct the image of the
emitting sources, for energies between 3 and 12 keV. We found that all tested algorithms give consistent results for the peak
position, while the other parameters can differ at most by a factor 2. Pixon and Forward-fit generally converge to similar results but Pixon is more reliable for reconstructing a complex source. We investigated the spectral characteristics of the two flares during
their evolution in the 3–25 keV energy band. We found that a single thermal model of the photon spectrum is inadequate to
fit the observations and we needed to add either a non-thermal model or a hot thermal one. The non-thermal and the double
thermal fits are comparable. If we assume a non-thermal model, the non-thermal energy is always higher than the thermal one.
Only during the very final decay phase a single thermal model fits the observed spectrum fairly well. 相似文献
7.
K. Wilhelm L. Abbo F. Auch��re N. Barbey L. Feng A. H. Gabriel S. Giordano S. Imada A. Llebaria W. H. Matthaeus G. Poletto N.-E. Raouafi S. T. Suess L. Teriaca Y.-M. Wang 《Astronomy and Astrophysics Review》2011,19(1):1-70
Coronal plumes, which extend from solar coronal holes (CH) into the high corona and??possibly??into the solar wind (SW), can now continuously be studied with modern telescopes and spectrometers on spacecraft, in addition to investigations from the ground, in particular, during total eclipses. Despite the large amount of data available on these prominent features and related phenomena, many questions remained unanswered as to their generation and relative contributions to the high-speed streams emanating from CHs. An understanding of the processes of plume formation and evolution requires a better knowledge of the physical conditions at the base of CHs, in plumes and in the surrounding inter-plume regions. More specifically, information is needed on the magnetic field configuration, the electron densities and temperatures, effective ion temperatures, non-thermal motions, plume cross sections relative to the size of a CH, the plasma bulk speeds, as well as any plume signatures in the SW. In spring 2007, the authors proposed a study on ??Structure and dynamics of coronal plumes and inter-plume regions in solar coronal holes?? to the International Space Science Institute (ISSI) in Bern to clarify some of these aspects by considering relevant observations and the extensive literature. This review summarizes the results and conclusions of the study. Stereoscopic observations allowed us to include three-dimensional reconstructions of plumes. Multi-instrument investigations carried out during several campaigns led to progress in some areas, such as plasma densities, temperatures, plume structure and the relation to other solar phenomena, but not all questions could be answered concerning the details of plume generation process(es) and interaction with the SW. 相似文献
8.
We present observations of Ovi 1032 Å line profiles obtained with the SUMER instrument on SOHO extending from the solar disk to 1.5 R
above the limb in the north polar coronal hole. Variations of the intensity and linewidth in the polar plume and inter-plume regions are investigated. We find an anti-correlation between the intensity and the linewidth in the plume and inter-plume regions with detailed plume structures been seen out to 1.5 R
. Possible implications regarding the magnetic topologies of these two regions and related heating mechanisms are discussed. The Ovi linewidth measurements are combined with UVCS output to provide an overview of its variations with height extending up to 3.5 R
. We find a linear increase of the linewidth from 1 to 1.2 R
, then a plateau followed by a sharp increase around 1.5 R
. 相似文献
9.
Hardi Peter L. Abbo V. Andretta F. Auchère A. Bemporad F. Berrilli V. Bommier A. Braukhane R. Casini W. Curdt J. Davila H. Dittus S. Fineschi A. Fludra A. Gandorfer D. Griffin B. Inhester A. Lagg E. Landi Degl’Innocenti V. Maiwald R. Manso Sainz V. Martínez Pillet S. Matthews D. Moses S. Parenti A. Pietarila D. Quantius N. -E. Raouafi J. Raymond P. Rochus O. Romberg M. Schlotterer U. Schühle S. Solanki D. Spadaro L. Teriaca S. Tomczyk J. Trujillo Bueno J. -C. Vial 《Experimental Astronomy》2012,33(2-3):271-303
The magnetic field plays a pivotal role in many fields of Astrophysics. This is especially true for the physics of the solar atmosphere. Measuring the magnetic field in the upper solar atmosphere is crucial to understand the nature of the underlying physical processes that drive the violent dynamics of the solar corona—that can also affect life on Earth. SolmeX, a fully equipped solar space observatory for remote-sensing observations, will provide the first comprehensive measurements of the strength and direction of the magnetic field in the upper solar atmosphere. The mission consists of two spacecraft, one carrying the instruments, and another one in formation flight at a distance of about 200 m carrying the occulter to provide an artificial total solar eclipse. This will ensure high-quality coronagraphic observations above the solar limb. SolmeX integrates two spectro-polarimetric coronagraphs for off-limb observations, one in the EUV and one in the IR, and three instruments for observations on the disk. The latter comprises one imaging polarimeter in the EUV for coronal studies, a spectro-polarimeter in the EUV to investigate the low corona, and an imaging spectro-polarimeter in the UV for chromospheric studies. SOHO and other existing missions have investigated the emission of the upper atmosphere in detail (not considering polarization), and as this will be the case also for missions planned for the near future. Therefore it is timely that SolmeX provides the final piece of the observational quest by measuring the magnetic field in the upper atmosphere through polarimetric observations. 相似文献
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