Joint vector magnetograph observations at BBSO,Huairou Station and Mees Solar Observatory     

Haimin Wang  John Varsik  Harold Zirin  Richard C. Canfield  K. D. Leka  Jingxiu Wang 《Solar physics》1992,142(1):11-20

Joint vector magnetograph observations were carried out at Big Bear Solar Observatory (BBSO), Huairou Solar Observing Station (Huairou), and Mees Solar Observatory (MSO) in late September 1989. Comparisons of vector magnetograms obtained at the three stations show a high degree of consistency in the morphology of both longitudinal and transverse fields. Quantitative comparisons show the presence of noise, cross-talk between longitudinal field and transverse field, Faraday rotation and signal saturation effects in the magnetograms. We have tried to establish how the scatter in measurements from different instruments is apportioned between these sources of error.  相似文献   

The absence of flares in λ3835 and the heating of the chromosphere     

Harold Zirin 《Solar physics》1972,26(2):393-396

Simultaneous observations of flares in H and a band 15 Å wide centered on 3835 Å show no change whatever in 3835 Å at the time of several flares, although the chromospheric network is easily visible. Flares are therefore transparent in this wavelength.Since the flare represents a test heat input from above, and no brightening of the network appears, we conclude it is impossible for the corona to produce the bright network by downward convection.  相似文献   

The solar flares of August 28 and 30, 1966     

Harold Zirin  D. Russo Lackner 《Solar physics》1969,6(1):86-103

We describe observations of the class 3+ flare of August 28, 1966, made at the Mount Wilson Observatory. This great proton flare followed the sequence: (1) Precursor flare; (2) Filament eruption; (3) Beginning in penumbra of large spot; (4) Rapid elongation in two strands; (5) Great spray and surface wave; (6) Rapid separation of two strands to maximum brightness; and (7) Slow spread of brightness and decay.The soft X-ray burst coincides with stages 3–6, decaying through stage 7; the hard (> 80 keV) burst coincides, but decays more rapidly.Considering a demi-cylinder of emitting material, the soft X-rays are explained by a 4-million-degree plasma, or at least a large flux of electrons with that amount of energy. Given this flux, the microwave burst is explained by synchrotron emission with the low frequency cut-off due to coronal absorption.The class-2 flare of August 30, 1966, is also discussed.This research was supported by the Advanced Research Projects Agency under the Office of Naval Research Grant N00014-67-C-0140 and the National Aeronautics and Space Administration under Grant NGR 05 002 034.NASA International University Fellow at the California Institute of Technology, 1967–1968, now at Arcetri Astrophysical Observatory.  相似文献   

Arch filaments associated with the formation of sunspots by umbral merging     

Harold Zirin 《Solar physics》1987,114(2):239-244

The formation of a sunspot during the emergence of a new group is described. The spot forms from a cluster of small umbrae that do not converge. Rather, the individual umbrae enlarge and merge into a spot covering the same area. The formation of each umbra is accompanied by an intensification of the arch filament anchored in it. The formation of the sunspot produces no apparent change in the total field.  相似文献   

Electromagnetic and corpuscular emission from the solar flare of 1991 June 15: Continuous acceleraton of relativistic particles     

L. G. Kocharov  G. A. Kovaltsov  G. E. Kocharov  E. I. Chuikin  I. G. Usoskin  M. A. Shea  D. F. Smart  V. F. Melnikov  T. S. Podstrigach  T. P. Armstrong  H. Zirin 《Solar physics》1994,150(1-2):267-283

Data on X-,γ-ray, optical and radio emission from the 1991 June 15 solar flare are considered. We have calculated the spectrum of protons that producesγ-rays during the gradual phase of the flare. The primary proton spectrum can be described as a Bessel-function-type up to 0.8 GeV and a power law with the spectral index ≈3 from 0.8 up to 10 GeV or above. We have also analyzed data on energetic particles near the Earth. Their spectrum differed from that of primary protons producingγ-ray line emission. In the gradual phase of the flare additional pulses of energy release occurred and the time profiles of cm-radio emission andγ-rays in the 0.8–10 MeV energy band and above 50 MeV coincided. A continuous and simultaneous stochastic acceleration of the protons and relativistic electrons at the gradual phase of the flare is considered as a natural explanation of the data.  相似文献   

Versuch zur Bestimmung von μmax undK s mit dem Sapromat-Verfahren     

Dr. Anna Halász 《Aquatic Sciences - Research Across Boundaries》1972,34(1):105-114

Ohne Zusammenfassung Die Arbeit wurde im Rahmen eines WHO-Stipendiuma an der Eidg. Anstalt für Wasserversorgung, Abwasserreinigung und Gew?sserschutz (EAWAG), Dübendorf, durchgeführt.  相似文献   

Emerging flux in active regions     

Margaret Liggett  Harold Zirin 《Solar physics》1985,97(1):51-58

We have compared the rates at which flux emerges in active and quiet solar regions within the sunspot belts. The emerging flux regions (EFRs) were identified by the appearance of arch filament structures in H. All EFRs in high-resolution films of active regions made at Big Bear in 1978 were counted. The comparable rate of flux emergence in quiet regions was obtained from SGD data and independently from EFRs detected outside the active region perimeter on the same films. The rate of flux emergence is 10 times higher in active regions than in quiet regions. A sample of all active regions in 31 days of 1983 gave a ratio of 7.5. We discuss possible mechanisms which might funnel new magnetic flux to regions of strong magnetic field.  相似文献   

Properties and Motions of Ellerman Bombs     

Nindos  Alexander  Zirin  Harold 《Solar physics》1998,182(2):381-392

We studied the properties and proper motions of Ellerman bombs (EBs) around a sunspot in a mature active region using high-resolution off-band H filtergrams together with nearly simultaneous magnetograms. Sixty-four percent of the EBs (class I) did not correspond accurately to enhanced magnetic field elements while the rest corresponded well to such elements (class II), which all were moving magnetic features (MMFs). We studied the lifetimes, shapes and dimensions, contrasts and time profiles of the EBs. These properties were essentially the same for both classes, in agreement with previous authors. Class I EBs did not move but class II EBs tracked the MMFs well, with horizontal proper motions up to a maximum of 1.1 km s–1 and their velocity pattern was similar to the velocity pattern of the MMFs.  相似文献   

A 10-Year Set of Ca II K-Line Filtergrams     

Anders Johannesson  William H. Marquette  Harold Zirin 《Solar physics》1998,177(1-2):265-278

We have processed a 10-year set of BBSO Caii K-line filtergrams covering most of solar cycle 22. The excess K-line emission is integrated to form linear and square-root activity indices that are fitted to UV data from UARS and SME. Good fits are found both for the Mgii core–wing ratio (linear) and total L irradiance (square root) and the indices are thus good proxies for UV data. The SME L irradiance is systematically lower by 20% than predicted from our corresponding K-line indices. The 10.7 cm radio data confirms that SME underestimated the flux. The network is partly responsible for the solar cycle variation of the indices and is relatively more important in L than in Mgii and Caii K. This is due to the saturation of L equivalent width. We also report on substantial improvements to the equipment and reduction software. The system is now based on a digital CCD camera which promises more accurate measurements in the upcoming solar cycle 23.  相似文献   

Study of Hα Jets on the Quiet Sun     

Haimin Wang  Anders Johannesson  Mike Stage  Chikyin Lee  Harold Zirin 《Solar physics》1998,178(1):55-69

High-speed jets of solar quiet regions have been observed at Big Bear Solar Observatory in H–1.0 Ú, and compared with high-resolution magnetograms. Over the whole Sun, the birthrate of the H–1.0 Ú jets is about 19±3 events s^–1, which is much lower than the birthrate of spicules. The average lifetime of these jets is 2±1 min. H–1.0 Ú jets are very different from spicules, in the sense of birthrate, lifetime, and shape. Jets tend to recur in the same sites, always located in boundaries of supergranules. Under the best observing conditions, we found that 80% of the major jet sites are associated with converging magnetic dipoles – mainly the sites where intranetwork elements are canceling with opposite polarity network elements. In order to establish a possible relationship between the disk H jets and limb macrospicules, we have also obtained time sequences of H center-line images at the limb. These images are enhanced by median filtering so that jet structures over the limb are easily studied. We found that these limb H jets (above the spicule forest) repeatedly occur in the same sites, which is the property shared by the disk H–1.0 Ú jets. However, their mean lifetime is 10 min, substantially longer than that of disk jets. Comparison with simultaneous SOHO/EIT Heii 304 Ú images shows that every Heii 304 Ú jet over the limb coincides with an H jet, although Heii 304 Ú jets extend much farther out. Some H jets do not have associated He jets, probably due to the difference in image resolutions. H spectra of selected jets are analyzed, and we found that jets are not simply blue-shifted; instead, the line profiles are broadened with significantly larger broadening on the blue side. Two-component fitting finds that the velocity of the blue-shifted component (an optically-thin component) is around 20 to 40 km s^–1.  相似文献