共查询到20条相似文献,搜索用时 13 毫秒
1.
E. E. Benevolenskaya 《Geomagnetism and Aeronomy》2013,53(7):891-895
The solar polar magnetic field has attracted the attention of researchers since the polar magnetic field reversal was revealed in the middle of the last century (Babcock and Livingston, 1958). The polar magnetic field has regularly reversed because the magnetic flux is transported from the sunspot formation zone owing to differential rotation, meridional circulation, and turbulent diffusion. However, modeling of these processes leads to ambiguous conclusions, as a result of which it is sometimes unclear whether a transport model is actual. Thus, according to the last Hinode data, the problem of a standard transport model (Shiota et al., 2012) consists in that a decrease in the polar magnetic flux in the Southern Hemisphere lags behind such a decrease in the flux in the Northern Hemisphere (from 2008 to June 2012). On the other hand, Svalgaard and Kamide (2012) consider that the asymmetry in the sign reversal simply results from the asymmetry in the emerging flux in the sunspot formation region. A detailed study of the polar magnetic flux evolution according to the Solar Dynamics Observatory (SDO) data for May 2010–December 2012 is illustrated in the present work. Helioseismic & Magnetic Imager (HMI) magnetic data in the form of a magnetic field component along the line of sight (the time resolution is 720 s) are used here. The magnetic fluxes in sunspot formation regions and at high latitudes have been compared. 相似文献
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The velocity field of large-scale magnetic structures during fast reorganizations of the global solar magnetic field structure
has been analyzed. Some characteristic features of the velocity field have been found during these periods. At that time,
a considerable part of the solar surface is occupied by regions with low horizontal velocities, which correspond to the regions
of positive and negative velocity field divergence during the solar activity growth and decline phases, respectively. Such
character of changes in the velocity field during these periods agrees with the previously proposed scenario of magnetic field
variations during global reorganizations of the magnetic field structure. The average horizontal velocities during a Carrington
rotation and their divergence have been calculated for Carrington rotations from 1646 to 2006. Relatively slow regular variations
in these parameters as well as their abrupt changes, observed during different solar cycle phases, have been revealed. An
increase in the average horizontal velocity during the solar activity growth phase is most probably caused by relative motions
of the regions with a new emerging magnetic flux. We assume that abrupt increases in the average horizontal velocity divergence
are related to fast reorganizations of the magnetic field structure. 相似文献
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《地震地磁观测与研究》2016,(1)
为了"佐证"地磁场的铁磁体"假说",通过对铁磁体试件加热退磁,在外加磁场作用下冷却、重新磁化实验,成功实现永磁铁磁极性倒转,结合铁磁体居里点可随压强增大而提高的推理,认为地磁场的形成应由内地核铁镍物质的铁磁性引起,并主要通过(下)地幔和液态外地核圈层对的对流变动对内地核温压条件的改变,实现地磁场从具磁性→退磁→恢复磁性进程的地磁场倒转,通过进一步的高温高压模拟实验,可望揭开地磁场的形成及倒转之谜。 相似文献
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Henry C. Halls 《Earth and Planetary Science Letters》1991,105(1-3)
Consistent age relationships between oppositely magnetized dykes of the 2.45 Ga Matachewan dyke swarm suggest that only a single magnetic field reversal occurred during the period of igneous activity. The magnetic field throughout most of this time was characterized by a SSW declination and shallow negative inclination but reversed toward the waning stages of magmatism. The new paleomagnetic data provide the oldest known magnetic reversal for which the relative reversal sense is known. 相似文献
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Jagdeo Singh 《Pure and Applied Geophysics》1970,82(1):165-188
Summary The present paper deals with the inverse polarization of rocks. At present there are two schools of thought to explain the inverse polarization. On the one hand, it is assumed that the geomagnetic field might have been reversed in those periods, when the rock formations took place. On the other it is advocated that it might be due to some intrinsic property of the rocks. To distinguish between the two theories, the author has studied the thermal demagnetization of a large number of rock samples from the Isle of Mull and has come to the conclusion that the inverse polarization is not due to an intrinsic property of the rocks as suggested byNéel, but to the reversal of the geomagnetic field. Some experimental details are also described in the paper. 相似文献
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A. V. Frank-Kamenetsky G. B. Burns O. A. Troshichev V. O. Papitashvili E. A. Bering W. J. R. French 《Journal of Atmospheric and Solar》1999,61(18):402
The vertical geoelectric field measured at Vostok, Antarctica (78.5°S, 107°E, L=75.0) over the 13 month interval May 1979–May 1980 is correlated with the interplanetary magnetic field (IMF) components By and Bz at times when Vostok is connected to the dayside magnetosphere. No significant association with IMF Bx is found. The interaction of the solar wind and the Earth’s magnetic field generally results in anti-sunward plasma flow in the high-latitude, polar ionosphere driven by a dawn-to-dusk, cross polar cap potential difference pattern. Using the IZMEM model to infer the contribution of the cross polar cap potential difference to the potential difference between the ionosphere and the ground at Vostok for the measured IMF conditions, we show that this provides a viable mechanism for the IMF associations found. We demonstrate that the direct association of the geoelectric field with the cross polar cap potential difference is independent of a result (Park, 1976. Solar magnetic sector effects on the vertical atmospheric electric field at Vostok, Antartica. Geophysical Research Letters 3(8), 475–478) showing an 15% decrease in the vertical geoelectric field measured at Vostok, 1–3 days after the passage of IMF sector boundaries. Evidence is also presented supporting the Park result, for which a mechanism is yet to be confirmed. 相似文献
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Prof. Dr. John Xanthakis 《Pure and Applied Geophysics》1960,46(1):11-22
Summary Within each sunspot cycle the yearly means (A) of the daily sunspot areas increase faster than the corresponding sunspot numbers (R) from the minimum to the maximum of solar activity and then decrease also faster than these numbers till the next minimum. Relation (A)=16.7 (R), frequently used so far, is approximately valid only for the years in the vicinity of the sunspot maximum. Instead of that, author gives the relations:
for the years preceding the sunspot maximum,
for the years following the sunspot maximum, wherea andb are constants,T
R
is the time of rise of the corresponding sunspot cycle expressed in years, andk takes the valuek=0 for the year of maximum solar activity andk=1, 2, 3, ... for the first, second, third ... year preceding or following that of maximum solar activity. The monthly means of the daily sunspot areas show a similar variation, but in this case the ratioq=AR varies with a greater amplitude both within each sunspot cycle and from cycle to cycle. The values ofq corresponding to all months of a given year in the sunspot cycle are contained between two limits depending on the time of rise.
Résumé Les valeurs moyennes (A) des aires diurnes des taches solaires à chaque année depuis 1878 augmentent plus rapidement du minimum vers le maximum de l'activité solaire que les nombres de Wolf correspondants (R). Elles diminuent aussi plus rapidement que les nombres de Wolf du maximum vers le minimum de l'activité solaire. La relation adoptée (A)=16.7 (R) ne s'applique pas avec une approximation satisfaisante que seulement pour les années voisines celle du maximum de l'activité solaire. L'auteur propose les relations: pour les années qui précédent le maximum, pour les années qui suivent le maximum, oùa, b sont des constantes,T R le temps d'ascension du cycle correspondant exprimé en années et la parametrek prend la valeurk=0 à l'année du maximum de l'activité solaire etk=1, 2, 3 ... pour les années qui précédent et qui suivent celle du maximum. Les valeurs moyennes des aires diurnes des taches à chaque mois, suivent la même marche mais dans ce cas le rapportq=AR present des larges variations. Il oscille pourtant extre deux limites qui dependent du temps d'ascension.相似文献
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The data of continuous observations of ELF emissions (polar chorus) at South Pole Antarctic observatory (Φ = ?74.02°) for 1997–1999 and during the superstrong magnetic storms of October and November 2003 are analyzed. It has been established that an increase in polar chorus is as a rule observed during the initial and recovery phases of a magnetic storm at positive values of the IMF vertical component (IMF B z > 0). Under such conditions, South Pole is located in the region of closed field lines. It has been found that the generation of polar chorus at South Pole abruptly ceases during the storm main phase after the IMF B z southward turning and beginning of an intense substorm in the nightside auroral zone, probably, because this observatory appears in the region of projection of the open magnetosphere due to the expansion of the polar cap. 相似文献
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A. Mete Isikara 《Pure and Applied Geophysics》1973,104(1):544-552
Summary The sunspot cycle variation of the amplitude of the solar magnetic variation has been investigated for magnetically moderate, quiet and disturbed days at Istanbul for the period 1949–1968, and fairly good linear relationship has been found forZ andD components of the earth's magnetic field. In some cases, it is rather difficult to say that there is any linear relationship between sunspot number and the amplitude of theH component of the earth's magnetic field. Meanwhile,K indices has also been considered with sunspot number by means of multiple regression analysis to overcome some uncertainties in this investigation. 相似文献
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This work investigated an interrelationship between the monthly means of time derivatives of horizontal geomagnetic field, dH/dt, sunspot number, R z , and aa index for the period of substorms (from ?90 to ?1800 nT) during the years 1990–2009. A total of 232 substorms were identified during the period of study. The time derivative of horizontal geomagnetic field, dH/dt, used as a proxy for geomagnetically induced current (GIC) exhibited high positive correlation with sunspot number (0.86) and aa index (0.8998). The obtained geomagnetic activity is in 92.665% explicable by the combined effect of sunspot number and aa index. The distribution of substorms as a function of years gives a strong support for the existence of geomagnetic activity increases, which implies that as the sunspot number increases the base level of geomagnetic activity increases too. 相似文献
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文采用球坐标下2.5维理想MHD模型,对日球子午面内方位磁场扰动的传播进行数值模拟,重点分析它对行星际磁场螺旋角的影响. 本文认为,观测到的行星际磁场螺旋角大于Parker模型的预言值,是太阳表面不断向行星际发出同向方位磁场扰动的结果;太阳较差自转在太阳内部产生的方位磁场为这类扰动提供了源头. 模拟结果表明,采用持续时间等于周期的十分之一、扰动幅度为103nT量级的正向方位磁场扰动,就可使1 AU处行星际磁场的螺旋角增加2°左右,与有关观测结果相符. 模拟结果还表明,上述方位磁场扰动对日球子午面内的太阳风特性和磁场位形的影响基本上可以忽略. 相似文献
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Summary It has been predicted that the geomagnetic field strength will be at its highest during periods of low reversal frequency. Using basaltic lavas from Israel and India, which were erupted during the 35 Ma interval of normal polarity in the mid-Cretaceous (the Cretaceous Quiet Zone), we have obtained palaeointensity estimates. The mean virtual dipole moments from the two areas are about 75% of the present value. This suggests that there is no simple relationship between the time averaged strength of the dipole and the frequency of reversals. 相似文献
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R. Hide 《Physics of the Earth and Planetary Interiors》1985,39(4):297-300
This note summarizes recent studies of atmospheric excitation of short-term changes in the length of the day and polar motion which set useful limits on the timescales associated with angular momentum transfer between the Earth's core and mantle. It also speculates about the nature of the recently-discovered phenomenon of “impulses” or “jerks” in the geomagnetic secular variation, proposing that they might be manifestations of “loop” instability of the magnetic field within the core. Finally, it outlines novel properties of high magnetic Reynolds number flows that bear on the inverse problem of deducing core motions from geomagnetic secular variation data. 相似文献
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The phenomenon of long-period sunspot oscillations with periods from several tens to a thousand minutes is studied using data on the magnetic field strength and sunspot coordinates obtained based on the SOHO MDI data. It has been indicated that oscillations of the sunspot magnetic field strength are related to relative and absolute horizontal oscillation modes, as a result of which certain limitations are imposed on the interpretation of the phenomenon. 相似文献
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The International Geomagnetic Reference Field models (IGRF) for 1900–2000 are used to calculate the geomagnetic field distribution
in the Earth’ interior from the ground surface to the core-mantle boundary (CMB) under the assumption of insulated mantle.
Four reversed polarity patches, as one of the most important features of the CMB field, are revealed. Two patches with +Z
polarity (downward) at the southern African and the southern American regions stand out against the background of ™Z polarity
(upward) in the southern hemisphere, and two patches of ™Z polarity at the North Polar and the northern Pacific regions stand
out against the +Z background in the northern hemisphere. During the 1900–2000 period the southern African (SAF) patch has
quickly drifted westward at a speed of 0.20–.3° /a; meanwhile its area has expanded 5 times, and the magnetic flux crossing
the area has intensified 30 times. On the other hand, other three patches show little if any change during this 100-year period.
Extending upward, each of the reversed polarity patches at the CMB forms a chimney-shaped “reversed polarity column” in the
mantle with the bottom at the CMB. The height of the SAF column has grown rapidly from 200km in 1900 to 900km in 2000. If
the column grows steadily at the same rate in the future, its top will reach to the ground surface in 600–700 years. And then
a reversed polarity patch will be observed at the Earth’s surface, which will be an indicator of the beginning of a magnetic
field reversal. On the basis of this study, one can describe the process of a geomagnetic polarity reversal, the polarity
reversal may be observed firstly in one or several local regions; then the areas of these regions expand, and at the same
time, other new reversed polarity regions may appear. Thus several poles may exist during a polarity reversal. 相似文献