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1.
Joseph B. Gurman 《Solar physics》1987,108(1):61-75
Time series observations of the profile of the Mgii k line 2795.52 have been obtained in five sunspots with the Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission. The three sunspots with umbrae larger than the 3 × 3 pixel size show significant oscillations in integrated line intensity and line centroid, with frequencies in the range 5.29–7.55 mHz (periods of 132–190 s).The frequencies of significant peaks in average umbral power spectra agree well with the frequencies of the three lowest-frequency transmission peaks predicted by a model of resonant transmission of acoustic waves. If radiative delays are unimportant, and the line centroid can be interpreted straightforwardly as a Doppler shift, the measured velocity-intensity phase differences indicate the superposition of upward- and downward-propagating waves in the umbral chromosphere; this is further evidence for the resonant transmission model.A single, quiet Sun time series of k core profiles yields power spectra and a phase difference consistent with the existence of a chromospheric p-mode.The SMM data used in this work were available only because of the repair of the SMM spacecraft by the crew of Challenger on mission 41-C. The pilot for that mission and the commander of Challenger's last mission was Francis R. Scobee.This work is dedicated to his memory. 相似文献
2.
J. B. Gurman 《Solar physics》1984,90(1):13-15
Observations of the Mgii h line in the umbrae of five sunspots show a spread of a factor of 3 in peak intensity. This range is larger than, and brackets, the range found in a single umbra by Lites and Skumanich (1982). 相似文献
3.
Lites B.W. Card G. Elmore D.F. Holzer T. Lecinski A. Streander K.V. Tomczyk S. Gurman J.B. 《Solar physics》1999,190(1-2):185-206
Solar Physics - This paper presents first observations of dynamics of the white-light solar corona detected during the few minutes of totality of a solar eclipse. Perturbations of a polar plume... 相似文献
4.
L. V. Didkovsky D. L. Judge A. R. Jones E. J. Rhodes J. B. Gurman 《Astronomische Nachrichten》2006,327(4):314-320
An indirect proton flux measuring tool based on discrimination of the energy deposited by protons in 128 × 128 pixel EIT CCD areas outside the solar disk images is presented. Single pixel intensity events are converted into proton incident energy flux using modeled energy deposition curves for angles of incidence ±60° in four EIT spatial areas with different proton stopping power. The extracted proton flux is corrected for both the loss of one‐pixel events in the range of angles of incidence as well as for the contribution to the single pixel events resulting from scattered middle‐energy protons (low‐energy or high‐energy particles are stopped by the EIT components or pass through them, accordingly). A simple geometrical approach was found and applied to correct for a non‐unique relation between the proton‐associated CCD output signal and the incident proton energy. With this geometrical approximation four unique proton incident energy ranges were determined as 45–49, 145–154, 297–335, and 390–440 MeV. The indirect proton flux measuring tool has been tested by comparing Solar Energetic Particles (SEP) flux temporal profiles extracted from the EIT CCD frames and downloaded from the GOES database for the Bastille Day (BD) of 2000 July 14 and the more recent 2005 January 20 events. The SEP flux temporal profiles and proton spectra extracted from the EIT in the relatively narrow energy ranges between 45 and 440 MeV reported here are consistent with the related GOES profiles. The four additional EIT extracted ranges provide higher energy resolution of the SEP data. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
EIT: Extreme-ultraviolet Imaging Telescope for the SOHO mission 总被引：10，自引：0，他引：10
J. -P. Delaboudinière G. E. Artzner J. Brunaud A. H. Gabriel J. F. Hochedez F. Millier X. Y. Song B. Au K. P. Dere R. A. Howard R. Kreplin D. J. Michels J. D. Moses J. M. Defise C. Jamar P. Rochus J. P. Chauvineau J. P. Marioge R. C. Catura J. R. Lemen L. Shing R. A. Stern J. B. Gurman W. M. Neupert A. Maucherat F. Clette P. Cugnon E. L. Van Dessel 《Solar physics》1995,162(1-2):291-312
The Extreme-ultraviolet Imaging Telescope (EIT) will provide wide-field images of the corona and transition region on the solar disc and up to 1.5 R above the solar limb. Its normal incidence multilayer-coated optics will select spectral emission lines from Fe IX (171 ), Fe XII (195 ), Fe XV (284 ), and He II (304 ) to provide sensitive temperature diagnostics in the range from 6 × 104 K to 3 × 106 K. The telescope has a 45 x 45 arcmin field of view and 2.6 arcsec pixels which will provide approximately 5-arcsec spatial resolution. The EIT will probe the coronal plasma on a global scale, as well as the underlying cooler and turbulent atmosphere, providing the basis for comparative analyses with observations from both the ground and other SOHO instruments. This paper presents details of the EIT instrumentation, its performance and operating modes. 相似文献
6.
Observations of a round, unipolar sunspot in the Zeeman triplet Fe i 6302.5 with the High Altitude Observatory Stokes Polarimeter are used to derive the vector magnetic field in the spot. The behavior of the magnitude, inclination, and azimuth of the field vector B across the spot is discussed. A linear relation is found between the continuum intensity I
c and the field magnitude B.
Time series obtained in the umbra show significant power in the magnitude of the field at a period of t 180 s but the other components of the field vector do not display this behavior.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
7.
Frank Hill Piet Martens Keji Yoshimura Joseph Gurman Joseph Hourclé George Dimitoglou Igor Suárez-Solá Steve Wampler Kevin Reardon Alisdair Davey Richard S. Bogart Karen Q. Tian 《Earth, Moon, and Planets》2009,104(1-4):315-330
The Virtual Solar Observatory (VSO) has been developed to allow researchers, educators, and the general public to access data and images from the major sources of on-line solar data. The VSO substantially reduces the effort required to locate disparate data sets, and removes the need for the user to locate the data and learn multiple interfaces. The VSO provides a single interface to about 60 geographically distributed data sets including space- and ground-based sources. These data sets incorporate several physical variables including magnetic field, intensity, Doppler velocity, etc., and all wavelengths from X-ray to radio. All layers of the sun, from the interior to the corona, are included. In this paper we describe the system and present the interface that the user will encounter. We also discuss future enhancements planned for the system. 相似文献
8.
In this letter, we bring attention to prominences which show different morphology in H and Heii 304 Å, as observed simultaneously by BBSO and EIT on board SOHO. Those two lines have been thought to represent similar chromospheric structures although they are formed at significantly different temperatures. We give two examples representing two kinds of anomaly: (1) prominences showing strong H emissions in the lower part and strong Heii emissions in the upper part, and (2) erupting prominences showing extensive Heii emission, but nothing in H. Our results indicate that a part or the whole of a prominence may be too hot to emit H radiation, possibly due to heating or thermal instability. Please note that these are not just two isolated cases, many other prominences show the similar differences in H and Heii 304 Å. 相似文献
9.
C. E. DeForest J. T. Hoeksema J. B. Gurman B. J. Thompson S. P. Plunkett R. Howard R. C. Harrison D. M. Hasslerz 《Solar physics》1997,175(2):393-410
On 7 and 8 March 1996, the SOHO spacecraft and several other space- and ground-based observatories cooperated in the most
comprehensive observation to date of solar polar plumes. Based on simultaneous data from five instruments, we describe the
morphology of the plumes observed over the south pole of the Sun during the SOHO observing campaign. Individual plumes have
been characterized from the photosphere to approximately 15 R⊙ yielding a coherent portrait of the features for more quantitative
future studies. The observed plumes arise from small (∼ 2-5 arc sec diameter) quiescent, unipolar magnetic flux concentrations,
on chromospheric network cell boundaries. They are denser and cooler than the surrounding coronal hole through which they
extend, and are seen clearly in both Feix and Fexii emission lines, indicating an ionization temperature between 1.0–1.5 x
106 K. The plumes initially expand rapidly with altitude, to a diameter of 20–30 Mm about 30 Mm off the surface. Above 1.2 R⊙
plumes are observed in white light (as ‘coronal rays’) and extend to above 12 R⊙. They grow superradially throughout their
observed height, increasing their subtended solid angle (relative to disk center) by a factor of ∼10 between 1.05 R⊙ and 4–5
R⊙ and by a total factor of 20–40 between 1.05 R⊙ and 12 R⊙. On spatial scales larger than 10 arc sec, plume structure in
the lower corona (R < 1.3 R⊙) is observed to be steady-state for periods of at least 24 hours; however, on spatial scales
smaller than 10 arc sec, plume XUV intensities vary by 10–20% (after background subtraction) on a time scale of a few minutes.
(Dr. Hassler is now employed by Southwest Research Institute, Boulder, CO) 相似文献
10.
Thompson B.J. Reynolds B. Aurass H. Gopalswamy N. Gurman J.B. Hudson H.S. Martin S.F. St. Cyr O.C. 《Solar physics》2000,193(1-2):161-180
We report coincident observations of coronal and chromospheric flare wave transients in association with a flare, large-scale coronal dimming, metric radio activity and a coronal mass ejection. The two separate eruptions occurring on 24 September 1997 originate in the same active region and display similar morphological features. The first wave transient was observed in EUV and H data, corresponding to a wave disturbance in both the chromosphere and the solar corona, ranging from 250 to approaching 1000 km s–1 at different times and locations along the wavefront. The sharp wavefront had a similar extent and location in both the EUV and H data. The data did not show clear evidence of a driver, however. Both events display a coronal EUV dimming which is typically used as an indicator of a coronal mass ejection in the inner corona. White-light coronagraph observations indicate that the first event was accompanied by an observable coronal mass ejection while the second event did not have clear evidence of a CME. Both eruptions were accompanied by metric type II radio bursts propagating at speeds in the range of 500–750 km s–1, and neither had accompanying interplanetary type II activity. The timing and location of the flare waves appear to indicate an origin with the flaring region, but several signatures associated with coronal mass ejections indicate that the development of the CME may occur in concert with the development of the flare wave. 相似文献