Search Results - (Author, Cooperation:Bumba)

2018-03-14

National Academy of Sciences

0027-8424

1091-6490

Biology

Medicine

Natural Sciences in General

Letters

0039-9140

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

1434-4726

Springer Online Journal Archives 1860-2000

Medicine

Electronic Resource

1437-1596

Springer Online Journal Archives 1860-2000

Medicine

Law

Electronic Resource

1432-2307

Springer Online Journal Archives 1860-2000

Medicine

Electronic Resource

1573-093X

Springer Online Journal Archives 1860-2000

Physics

Abstract Positions of active regions estimated from observations of the whole solar disk in Caii K iv during the period 1977–1989 at the Coimbra Astronomical Observatory are compared with the time-dependent latitudinal distribution of background solar magnetic fields and with the latitudinal shifts of boundaries of their polarities. We confirm that the sunspot groups are located near the zonal boundaries between the opposite polarities of the solar background magnetic field during different phases of the two recent consecutive cycles of activity. We demonstrate a probable connection between the increased number of groups and the commencement of poleward migration of zonal boundaries in both hemispheres. But the influence of the ‘dominant convective rolls’ seems to he still unclear. A new problem of interrelation between the zonal and sector boundaries has also appeared.

Electronic Resource

1573-093X

Springer Online Journal Archives 1860-2000

Physics

Abstract We discuss some problems concerning the influence of the behavior of background and local magnetic and velocity fields, and above all, of interconnections and interrelations of various phenomena of solar activity on the estimation of solar rotation rates.

Electronic Resource

1573-093X

Springer Online Journal Archives 1860-2000

Physics

Abstract A time series of K3 spectroheliograms taken at the Coimbra Observatory exhibits an erupting loop on the east limb on July 9, 1982 in active region NOAA 3804. The Goddard SMM Hard X-Ray Burst Spectrometer (HXRBS) observations taken during this period reveal a hard X-ray flare occurring just before the loop eruption is observed, and SMS-GOES soft X-ray observations reveal a strong long-duration event (LDE) following the impulsive phase of the flare. A Solwind coronagram exhibits a powerful coronal mass ejection (CME) associated with the erupting loop. Hα flare and prominence observations as well as centimeter and decimeter radio observations of the event are also reviewed. A large, north–south-oriented quiescent prominence reported within the upper part of the CME expansion region may play a role in the eruption as well. The spatial and temporal correlations among these observations are examined in the light of two different current models for prominence eruption and CME activation: (1) The CME is triggered by the observed hard X-ray impulsive flare. (2) The CME is not triggered by a flare, and the observed soft X-ray flare is an LDE due to reconnection within the CME ‘bubble’. It is concluded that this event is probably of a ‘mixed’ type that combines characteristics of models (1) and (2). The July 9 event is then compared to three other energetic CME and flare eruptions associated with the same active-region complex, all occurring in the period July 9 through September 4, 1982. It is noted that these four energetic events coincide with the final evolutionary phase of a long-lasting active-region complex, which is discussed in a companion paper (Bumba, Garcia, and Jordan, 1997). The paper concludes by addressing ‘the solar flare myth’ controversy in the light of this work.

Electronic Resource

1573-093X

Springer Online Journal Archives 1860-2000

Physics

Abstract Studying the appearance of active regions during periods of solar activity minima, we observed that the magnetic fields of active regions belonging to the old and new cycle were mutually related. This was the reason we decided to investigate the relation of the old and new cycle activity during the two last minima in more detail. We examined the distribution of both activities in heliographic longitude, because the patterns of such distribution change substantially during the time of the minimum, and we studied their relation to the distribution and development of the global (background) magnetic field. We observed that the active regions of the old and new cycles tended to concentrate in the same active longitudes. The sources of their magnetic fluxes seem to have the same heliographic longitude. The beginning of the new cycle activity, occurring at the very beginning to a very weak degree in the equatorial zone, and then proceeding to higher latitudes, occurs in the magnetic field remnants of the old cycle activity. During the transition phase, a relatively large number of small active regions is produced by both cycles.

Electronic Resource

1573-093X

Springer Online Journal Archives 1860-2000

Physics

Abstract The first small active regions of the last two new cycles seem to be formed, in its very first, preparatory stage, close to the equator with uncertain magnetic orientation, and as secondary products at the periphery of equatorial `magnetic bubbles' of the new magnetic flux still belonging to the old cycle. At the real beginning of the new cycle, at the periphery of its higher-latitude `magnetic bubbles', the opposite applies to the secondary regions of the ending cycle. It seems that two modes of magnetic flux supply the visible layers of the photosphere during the cycle transition phase: the emergence of the magnetic flux from the depth of the convective zone, and the mutual interaction of the earlier emerging fluxes, or the action of the `local dynamo', giving rise to the new local magnetic field concentrations.

Electronic Resource

1573-093X

Springer Online Journal Archives 1860-2000

Physics

Abstract The flare activity and especially the proton-flare activity is concentrated in the zones of ‘Bartels' active longitudes’ and in the neighbourhood closest to the sector boundaries of the interplanetary magnetic field. This concentration seems to be greater if the importance of the event increases.

Electronic Resource

1573-093X

Springer Online Journal Archives 1860-2000

Physics

Abstract A study of the Mount Wilson magnetic-field synoptic chart material divided into latitude zones for the interval 1959–67, and a comparison of the data with sunspot groups have provided a better understanding of the structure of the background-field pattern and its relation to activity. The interaction of old and new fields within the pattern seems to result in long-lived sections of alternating polarity in both hemispheres. We postulate subsurface sources with rotation periods of about 27 days which produce active regions over a longitude zone of some tens of degrees. There is a tendency for the background-field features with strong fields to resist to some extent the shearing effects of differential rotation. A prediction is made concerning the nature of the interplanetary magnetic field above the ecliptic.

Electronic Resource

1573-093X

Springer Online Journal Archives 1860-2000

Physics

Abstract We discuss the problems connected with the measurements and evaluation of line-of-sight velocities, obtained with a scanning photoelectric magnetograph using a line-shifter with enhanced sensitivity. We bring arguments for the validity of the results of our photoelectric Doppler velocity recordings. We have found a network of cellularly shaped patterns in the distribution of photo-electrically measured line-of-sight motions, upflowing in the magnetically quiet (blue-shifted) and downflowing in magnetically active (red-shifted) areas of the photosphere, if the mean velocity level is estimated for a sufficiently large measured area. The features of both directions are mutually complementary. We demonstrate the effect of the shift of the reference zero velocity level on the topology of the line-of-sight velocity maps, and the dependence of this level on the size of the area from which it is estimated.

Electronic Resource

1572-9486

Springer Online Journal Archives 1860-2000

Physics

Abstract This paper introduces a device for measurement of the modulation transfer function of photographic materials. The device is a realization of the method based on the incoherent imaging of a rectangular parallel wave grating with continuously varying spatial frequency in space to the photographic material under test by means of an auxiliary photographic objective of known properties. The theory of that method is shortly introduced, the principle of measurement is explained, the realized device is described and evaluated and some results of measurement are shown.

Electronic Resource

1572-946X

Springer Online Journal Archives 1860-2000

Physics

Abstract We have compared the latitudinal distributions of polar faculae, green coronal emission maxima, prominences and of a new index of enhanced geomagnetic recurrence with the distribution of magnetic fields during the cycles Nos. 20 and 21. We did not find a distinct high-latitude initial stage of an extended cycle in the corona, prominences and polar faculae distribution. On the contrary, it seems that the polar faculae and their following polarity magnetic fields represent the last evolutionary phase of a magnetic activity cycle lasting 15–17 years. The enhanced recurrent geomagnetic activity seems to be related to the old cycle fields. All studied phenomena clearly display two types of latitudinal distribution: the polar belts, into which the old following polarity fields have been transported from the equatorial belt where both the polarities developin situ simultaneously, but in which the leading polarity fields only remain, crossing the equator during the minimum of activity, to play the same role on the opposite hemispheres in the new cycle.

Electronic Resource

1572-946X

Springer Online Journal Archives 1860-2000

Physics

Abstract Earlier results concerning sympathetic flares - physically related flares occurring in different active regions practically in the same time - and time-correlated radio bursts are compared with magnetic situation in active regions with related flaring and with the history and dynamics of its development. We found observational evidence abou the reality of sympathetic flares, demonstrating also that active regions in which they appear are physically related through common dynamical elements in which the evolution of their magnetic fields goes parallel. Such a process may sometimes occupy a very large volume of the photosphere and we believe that it might be related to the large-scale convective motions.

Electronic Resource

1432-1335

Springer Online Journal Archives 1860-2000

Medicine

Electronic Resource

1573-1626

Springer Online Journal Archives 1860-2000

Architecture, Civil Engineering, Surveying

Geosciences

Physics

Summary The Interkosmos5 VLF experiment consisted of a spectrum analyser with twelve narrow-band channels and broadband measurements between0.07 and20 kHz using an analogue telemetry with a tape recorder on board. The apparatus used in the experiment is shortly described, some examples ofVLF phenomena observed are given and a review of all analogue data recorded is shown in a graphical calendar.

Electronic Resource

1573-1626

Springer Online Journal Archives 1860-2000

Architecture, Civil Engineering, Surveying

Geosciences

Physics

Summary Regularities in the solar background magnetic field distribution are described and some of their specific patterns and their structures are studied. The influence of the solar differential rotation on the behaviour of “Magnetic Active Longitudes” is demonstrated. The origin of some specific details different in both polarities is discussed. The relation of this longitudinal solar magnetic field distribution to the longitudinal distribution of the daily geomagnetic character figures C9 is investigated. Some correlational characteristics are given. The specific “Index of Geomagnetic Recurrence” is estimated and the changes of its values in time are demonstrated.

Резюме Оnuсывaюmся регулярносmu в рaсnре¶rt;еленuu солнечного фонового мaгнumного nоля u uзучamся некоmорые uз uх хaрaкmерных своŭсmв. Покaзывеmся влuянuе солнечного ¶rt;uфференцuaльного врaщенuя нa хо¶rt; „мaгнumных aкmuвных ¶rt;олгоm“. Дuскуmuруеmся nрuчuнa nоявленuя некоmорых сnецuфuческuх ¶rt;еmaлеŭ в uх сmрукmуре рaзнях в nроmuвоnоложных nолярносmях. Изучaеmся связь ¶rt;олгоmного рaсnре¶rt;еленuя солнечных мaгнumных nолеŭ с ¶rt;олгоmным рaсnре¶rt;еленuемгеомaгнumных возмущенuŭ. Прuво¶rt;яmся некоmорые корреляцuонные хaрaкmерuсmuкu эmоŭ связu. Оnре¶rt;еляеmся сnецuфuческuŭ „uн¶rt;ексгеомaгнumноŭ рекуренmносmu“ u ¶rt;емонсmрuруюmся uзмененuя его велuчuны со временем.

Electronic Resource

1573-8922

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Abstract By means of Thomasset two-frequency rheometry it has been established that a change in the total amount of body fluids in experimental animals is accompanied by a change in impedances, which indicates a redistribution of the extracellular and intracellular fluids for the purpose of maintaining the circulation.

Electronic Resource