Transient brightenings of interconnecting loops     

Zdeněk Švestka  Robert Howard 《Solar physics》1979,63(2):297-318

We study sudden brightenings of coronal loops that interconnect active regions. Such brightenings often occur within one or two days after the birth of a new interconnecting loop, as well as in some old interconnections. The brightenings of young loops are obviously associated with the emergence of new magnetic flux near their footpoints, whereas some enhancements of old loops may be triggered by slowly moving disturbances propagating from other centers of activity. A few loop brightenings are associated with flares, but the loop does not brighten in consequence of energy supply from the flare. Both the flare and the loop brightening are independent consequences of one common agent, presumably newly emerging flux.Temperatures in brightened loops are between 3 and 4 × 10⁶ K and densities are < 2 × 10⁹ cm^–3, probably < 5 × 10⁸ cm^–3 in some old loops. The top part of a loop is the site of the most intense brightening in the initial phase of a loop enhancement. The most frequent lifetime of these brightenings is 6 to 7 hr.Hale Observatories are operated jointly by the Carnegie Institution of Washington and the California Institute of Technology.  相似文献   

Seasonal variability of biological arsenic methylation in the estuary of the River Beaulieu     

A.G. Howard  M.H. Arbab-Zavar  S. Apte 《Marine Chemistry》1982,11(5):493-498

The observation of a strong seasonal variation of arsenic species found in the estuaries of the Rivers Beaulieu, Test and Itchen in central southern England is presented. The implications of such observations regarding the environmental biomethylation and fate of arsenic in natural waters are also discussed.  相似文献   

The rotation of active regions with differing magnetic polarity separations     

Robert F. Howard 《Solar physics》1992,142(2):233-248

The separation of the leading and following portions of plages and (multi-spot) sunspot groups is examined as a parameter in the analysis of plage and spot group rotation. The magnetic complexity of plages affects their average properties in such a study because it tends to make the polarity separations of the plages less than they really are (by the definition of polarity separation used here). Correcting for this effect, one finds a clear and very significant dependence of the total magnetic flux of a region on its polarity separation. Extrapolating this relationship to zero total flux leads to an X intercept of about 25 Mm in polarity separation. The average residual rotation rates of regions depend upon the polarity separation in the sense that larger separations correspond to slower rotation rates (except for small values of separation, which are affected by region complexity). In the case of sunspots, the result that smaller individual spots rotate faster than larger spots is confirmed and quantified. It is shown also that smaller spot groups rotate faster than larger groups, but this is a much weaker effect than that for individual spots. It is suggested that the principal effect is for spots, and that this individual spot effect is responsible for much or all of the group effect, including that attributed in the past to group age. Although larger spot groups have larger polarity separations, it is shown that the rotation rate-polarity separation effect is the opposite in groups than one finds in plages: groups with larger polarity separations rotate faster than those with smaller separations. This anomalous effect may be related to the evolution of plages and spot groups, or it may be related to connections with subsurface toroidal flux tubes. It is suggested that the polarity separation is a parameter of solar active regions that may shed some light on their origin and evolution.Operated by the Association of Universities for Research in Astronomy, Inc., under Cooperative Agreement with the National Science Foundation.  相似文献   

The GLE-associated flare of 21 August, 1979     

E. W. Cliver  S. W. Kahler  H. V. Cane  M. J. Koomen  D. J. Michels  R. A. Howard  N. R. Sheeley Jr. 《Solar physics》1983,89(1):181-193

We use a variety of ground-based and satellite measurements to identify the source of the ground level event (GLE) beginning near 06∶30 UT on 21 August, 1979 as the 2B flare with maximum at ～06∶15 UT in McMath region 16218. This flare differed from previous GLE-associated flares in that it lacked a prominent impulsive phase, having a peak ～9 GHz burst flux density of only 27 sfu and a ?20 keV peak hard X-ray flux of ?3 × 10^-6 ergs cm^-2s^-1. Also, McMath 16218 was magnetically less complex than the active regions in which previous cosmic-ray flares have occurred, containing essentially only a single sunspot with a rudimentary penumbra. The flare was associated with a high speed (?700 km s^-1) mass ejection observed by the NRL white light coronagraph aboard P78-1 and a shock accelerated (SA) event observed by the low frequency radio astronomy experiment on ISEE-3.  相似文献   

The coronal transient of 16 June 1972     

Koomen  Martin  Howard  Russell  Hansen  Richard  Hansen  Shirley 《Solar physics》1974,34(2):447-452

On 16 June 1972, the Naval Research Laboratory's coronagraph aboard OSO-7 tracked a huge coronal cloud moving outward from the Sun. Concurrent observations of the inner corona made by the High Altitude Observatory at Mauna Loa showed bifurcation of the underlying coronal structure. Together, these observations can be interpreted as evidence for the stretching of the closed fields into a magnetic bottle, extending to at least eight radii from the center of the Sun.  相似文献   

The mean magnetic field of the Sun: Method of observation and relation to the interplanetary magnetic field     

Philip H. Scherrer  John M. Wilcox  Valeri Kotov  A. B. Severny  Robert Howard 《Solar physics》1977,52(1):vi-12

The mean solar magnetic field as measured in integrated light has been observed since 1968. Since 1970 it has been observed both at Hale Observatories and at the Crimean Astrophysical Observatory. The observing procedures at both observatories and their implications for mean field measurements are discussed. A comparison of the two sets of daily observations shows that similar results are obtained at both observatories. A comparison of the mean field with the interplanetary magnetic polarity shows that the IMF sector structure has the same pattern as the mean field polarity.  相似文献   

The magnetic flux in the quiet sun network     

Barry J. Labonte  Robert Howard 《Solar physics》1982,80(1):15-19

The Ca ii K line emission from the quiet Sun network does not vary with the 11-year cycle (White and Livinston, 1981). We confirm this result from direct magnetic measurements. This effect is not simply explained by present empirical models of the evolution of surface magnetic fields.Now at Institute for Astronomy, University of Hawaii, Honolulu, Hawaii 96822, U.S.A.  相似文献   

WHEN ARE STORE LOCATIONS GOOD? THE CASE OF THE NATIONAL TEA COMPANY IN DETROIT     

Howard L. Green  William Applebaum  Herbert Dupree 《The Professional geographer》1978,30(2):162-167

Testing the theoretical notion that differences in entrepreneurial skill can enhance the viability of a poor location or detract from the qualities of a good location, this study reviews the historical experience of a number of retailing establishments operated by different firms at the same sites. The ultimate success of stores that had done poorly under previous management tends to confirm that a location is “good'’only so long as the retailer employs effective merchandising and operating policies.  相似文献   

Solar velocity fields: 5-min oscillations and supergranulation     

Andrew S. Tanenbaum  John M. Wilcox  Edward N. Franzier  Robert Howard 《Solar physics》1969,9(2):328-342

One dimensional magnetograph scans have been used to study the 5-min photospheric velocity oscillations and the supergranulation. The oscillations in wing brightness lead the oscillations in velocity by less than 90° in the photosphere, and about 90° in the chromosphere, suggesting that they are traveling waves at lower levels and standing waves at higher levels. Downward flows have been observed to be coincident with the chromospheric network confirming the hypothesis that material is flowing downward at supergranular boundaries.  相似文献   

Comments on “Metallic minerals,thermal histories and parent bodies of some xenolithic,ordinary chondrite meteorites” by E. R. D. Scott and R. S. Rajan (1980)     

A.W.R. Bevan  H.J. Axon 《Geochimica et cosmochimica acta》1981,45(10):1957-1958

Bevan and Axon (1980) proposed that polycrystalline γ (taenite) in the unequilibrated (H3) chondrite Tieschitz is a relic of rapid, non-equilibrium solidification of Fe-Ni-S melts during chondrule formation. Scott and Rajan (1980) dismissed our observations and conclusions. Here we defend and clarify our position. Grain boundaries as observed in polycrystalline γ(taenite) could not have been established either during slow, sub-solidus cooling of homogeneous γ(taenite), or, in the absence of γ/γ grain-boundary α precipitates, by deformation and annealing (hot working).  相似文献