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1.
Time variations in strong and weak photospheric magnetic fields have been considered based on synoptic maps from the Kitt Peak observatory for 1976?C2003. The magnetic fields of positive and negative polarities of the Northern and Southern hemispheres of the Sun and their imbalance were studied. It has been indicated that different groups of magnetic fields vary with 11-or 22-year periods depending on their values. The difference between positive and negative fluxes for each hemisphere always varies with a 22-year period. For weak fields, the 22-year cycle is related to the manifestation of the global solar magnetic field. For strong fields, the imbalance between positive and negative fluxes reflects the predominant role of leading sunspots in a given solar hemisphere. It has been detected that the total magnetic flux over the entire solar disk varies with an 11-year period in antiphase with the solar activity cycle for the weakest magnetic fields (0?C5 G).  相似文献   

2.
The results of investigations of the latitudinal distribution of annual variation of the geomagnetic field level in the seasons of 1964 (International Quiet Sun Year) using the data from 95 world magnetic observatories located at various longitudes in the latitude range 83° N–90° S are reported. The latitudinal features of the X, Y, and Z components of the geomagnetic field have been analyzed. It has been shown that the amplitudes (summer-winter differences) of the annual variation are maximal in the polar regions, decrease continuously to zero towards the equator, and are identical for both the Northern and Southern hemispheres with a half-year delay (local summer). The amplitudes of the equinox-winter difference in the equinox periods are smaller than those in summer, but are manifested simultaneously in the Northern and Southern hemispheres. An equivalent circumpolar current system has been constructed, which is responsible for the annual variation of the geomagnetic field level. Its parameters have been determined.  相似文献   

3.
The magnetic flux longitudinal distribution in the equatorial solar zone has been studied. The magnetic synoptic maps of the Wilcox Solar Observatory (WSO) during Carrington rotations (CRs) 2052–2068 in 2007 and early 2008 have been analyzed. The longitudinal distributions of the area of the zones where the photospheric magnetic field locally enhanced have been constructed for each CR. The obtained distributions indicate that the zones are located discretely and that a clearly defined one narrow longitudinal interval with the maximum flux is present. The longitudinal position of this maximum shifted discretely by ≈130° at an interval of 5.5 ± 0.5 CRs. A longitudinal shift of the zones with an increased magnetic flux multiple of 60° was observed between the hemispheres. In addition, a time shift of ≈2.5 CRs existed between the instants when the position of maximum fluxes in different hemispheres shifted. The established peculiarities of the magnetic flux longitudinal distribution and time dynamics are interpreted as an action of supergiant convection cells. These actions result in that magnetic fields are removed from the generation region through the channels that are formed between such cells at a longitudinal interval of 120°. The average synodic rotation velocity of the considered equatorial channels, through which the magnetic flux emerges, is 13.43° day–1.  相似文献   

4.
A new method for determining geomagnetic activity based on calculation of the hourly amplitudes of geomagnetic field variations at ground-based observatories has been developed. Observations performed in 2009, when unusually low solar and geomagnetic activity was registered, were used as a reference level. The described method was used to estimate the energy of local geomagnetic activity; such energy is estimated for observatories in the Earth’s Northern and Southern hemispheres, and a total estimation is made for both hemispheres and for the entire Earth’s surface during large magnetic storms. These are used to compare characteristics of magnetic storm intensity based on the classical Kp and Dst indices and calculated energy estimate.  相似文献   

5.
The mathematical model of the magnetic field of the partial ring current has been proposed. This current is considered as a pair of spatial current circuits in the Northern and Southern hemispheres, either of which includes two ring zones, in the geomagnetic equator plane and ionosphere, and two zones of the field-aligned current, flowing along the geomagnetic dipole field lines and joining ring fragments of the circuit. The model parameters are: colatitude of the eastward electrojet, longitudinal shift relative to the Sun-Earth axis, circuit half-angle, and the total current flowing in the circuit. The Biot-Savart-Laplace law has been used to calculate the magnetic field of the current circuit. The magnetic field of the partial ring current has been calculated under the conditions typical of a strong magnetic storm. The technique for calculating the partial ring current intensity, using the Asym-H geomagnetic index, has been proposed.  相似文献   

6.
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   

7.
The ring current dynamics during the magnetic storm has been studied in the work. The response of the magnetospheric current systems to the external influence of the solar wind, specifically, resulting in the development of the asymmetric ring current component, has been calculated using the magnetic field paraboloid model. The asymmetric ring current has been considered as a family of spatial current circuits in the Northern and Southern hemispheres, composed of the zones of the partial ring current in the geomagnetic equator plane, which close through the system of field-aligned currents into the ionosphere. The value of the total partial ring current has been estimated by comparing the calculated asymmetry of the magnetospheric magnetic field at the geomagnetic equator with the value of the Asym-H geomagnetic index. The variations in the symmetric and asymmetric components of the ring current magnetic field have been calculated for the magnetic storm of November 6–14, 2004. The contributions of the magnetospheric current systems to the Dst and AU geomagnetic indices have been calculated.  相似文献   

8.
Based on the observations in six pairs of almost conjugate high-latitude stations in the Arctic and Antarctic regions, the spectral and spatial-temporal structures of long-period geomagnetic pulsations (f = 2–5 mHz) during the magnetic storm of April 16–17, 1999, which is characterized by a high (up to 20 nPa) solar wind dynamic pressure, have been studied. It has been indicated that the magnetic storm sudden commencement is accompanied by a symmetrical excitation of np pulsations near the dayside polar cusps with close amplitudes. Under the conditions when IMF B z > 0 and B y < 0, strong magnetic field variations with the periods longer than 15–20 min were observed only in the northern polar cap. When IMF B z and B y became close to zero, geomagnetic pulsation bursts in both hemispheres were registered simultaneously but differed in the spectral composition and spatial distribution. In the Northern Hemisphere, pulsations were as a rule observed in a more extensive latitude region than in the Southern Hemisphere. In the Northern Hemisphere, the oscillation amplitude maximum was observed at higher latitudes than in the Southern Hemisphere. The pulsation amplitude at geomagnetic latitude lower than 74° was larger in the Arctic Regions than in the Antarctic Regions. This can be explained by sharply different geographic longitudes in the polar cap and latitudes in the auroral zone, which results in a different ionospheric conductivity affecting the amplitude of geomagnetic pulsations.  相似文献   

9.
Data from HF-radars are used to make the first simultaneous conjugate measurements of the day-side reconnection electric field. A period of 4 h around local magnetic noon are studied during a geospace environment modeling (GEM) boundary layer campaign. The interplanetary magnetic field (IMF) was southward whilst the eastward component (By) was variable. The flow patterns derived from the radar data show the expected conjugate asymmetries associated with IMF |By| ≥ 0. High-time resolution data (50 and 100 s) enable the flow of plasma across the open/closed field line boundary (the separatrix) to be studied in greater detail than in previous work. The latitude of the separatrix follows the same general trend in both hemispheres but shows a hemispherical difference of 4°, with the summer cusp at higher latitude, as expected from dipole tilt considerations. However, the short-time scale motion of the separatrix cannot be satisfactorily resolved within the best resolution (300 m s−1) of the experiment. The orientation of the separatrix with respect to magnetic latitude is found to follow the same trend in both hemispheres and qualitatively fits that predicted by a model auroral oval. It shows no correlation with IMF By. However, the degree of tilt in the Northern (summer) Hemisphere is found to be significantly greater than that given by the model oval. The convection pattern data show that the meridian at which throat flow occurs is different in the two hemispheres and is controlled by IMF By, in agreement with empirically derived convection patterns and theoretical models. The day-side reconnection electric field values are largest when the radar’s meridian is in the throat flow or early afternoon flow regions. In the morning or afternoon convection cells, the reconnection electric field tends to zero away from the throat flow region. The reconnection electric field observed in the throat flow region is bursty in nature.  相似文献   

10.
Observations made by the Hinotori satellite have been analysed to determine the yearly variations of the electron density and electron temperature in the low-latitude topside ionosphere. The observations reveal the existence of an equinoctial asymmetry in the topside electron density at low latitudes, i.e. the density is higher at one equinox than at the other. The asymmetry is hemisphere-dependent with the higher electron density occurring at the March equinox in the Northern Hemisphere and at the September equinox in the Southern Hemisphere. The asymmetry becomes stronger with increasing latitude in both hemispheres. The behaviour of the asymmetry has no significant longitudinal and magnetic activity variations. A mechanism for the equinoctial asymmetry has been investigated using CTIP (coupled thermosphere ionosphere plasmasphere model). The model results reproduce the observed equinoctial asymmetry and suggest that the asymmetry is caused by the north-south imbalance of the thermosphere and ionosphere at the equinoxes due to the slow response of the thermosphere arising from the effects of the global thermospheric circulation. The observations also show that the relationship between the electron density and electron temperature is different for daytime and nighttime. During daytime the yearly variation of the electron temperature has negative correlation with the electron density, except at magnetic latitudes lower than 10°. At night, the correlation is positive.  相似文献   

11.
The global pattern of the ionospheric response to large-scale acoustic gravity waves (LS AGW) has been constructed on the basis of an analysis of the large data set available during the 22 March 1979, magnetic storm. Ground-based ionospheric measurements and in-situ satellite measurements from Cosmos-900 were used in this study together with the Joule heating distribution in the high-latitude ionosphere specifically taken at the maxima of two substorms. The characteristics of the reconstructed planetary pattern of the LS AGW have been analysed in detail. It has been established that the LS AGW effects in the ionosphere in terms of both universal and local time were determined by the pattern of high-latitude atmospheric heating, and that the wave front of the LS AGW during both substorms covered practically all local times, i.e. all longitudes. In addition, it was established that one of the sources of the LS AGW was the thermospheric heating in the day-side cusp region. The local time dependence of the amplitude of the AGW effect in both maximum height, hmF2, and critical frequency, fOF2, has been reconstructed for the mid-latitude F2 layer. The AGW effects were clearly separated from the electric field effects related to turnings of the interplanetary magnetic field (IMF) BZ. In the day-time, electric field effects prevailed over the AGW effects, but during the night-time the amplitudes of these two effects were comparable. In contrast to the common view, fOF2 variations after the AGW passage had a quasi-sinusoidal character both in the day-time and in the night-time. In the night-time ionosphere a high degree of symmetry was observed for the AGW effects in Northern and Southern hemispheres. During the day-time a significant asymmetry was observed in the American longitudinal sector which was related largely to the peculiarities of the heating pattern in the high-latitude ionospheres of the Northern and Southern hemispheres. These observations demonstrate the complexity of the response of the ionosphere at all latitudes to heating of the auroral region.  相似文献   

12.
Ionospheric disturbances at heights of the F 2 layer maximum during the strong magnetic storm (the minimum value of the Dst index was ?149 nT) and the magnetic superstorm (the minimum value of the Dst index was ?387 nT) have been compared based on the data from two pairs of magnetically conjugate midlatitude ground stations for ionospheric vertical sounding. The storms began on March 19, 2001, and March 31, 2001, respectively. It has been obtained that almost only negative ionospheric disturbances were observed in the Northern and Southern hemispheres in both cases. The maximum effect in changes in the layer critical frequency (foF2) in both hemispheres has a time delay relative to the moment of the maximum disturbance in the Dst index on the order of 3–4 h for the strong storm and about 1 h for the superstorm. The disturbed variations in the foF2 critical frequency in different hemispheres correlate well with each other in the plane of one magnetic meridian, but the correlation substantially weakens at different magnetic longitudes. An assumption is made that the revealed features of the behavior of the disturbed midlatitude ionospheric F 2 layer are caused by the complex character of the thermospheric response to the energy release in the auroral zone during the considered magnetic storms.  相似文献   

13.
An inter-hemispheric asymmetry is found in the characteristics of polar mesosphere summer echoes (PMSE) and upper mesosphere temperatures at conjugate latitudes (～69°) above Antarctica and the Arctic. The second complete mesosphere–stratosphere–troposphere (MST) radar summer observation season at Davis (68.6°S) revealed that PMSE occur less frequently, with lower strength and on average 1 km higher compared with their northern counterparts at Andenes (69.3°N). We consider the thermodynamic state of the mesosphere for conjoining hemispheric summers based on satellite and ground-based radar measurements, and show the mesopause region near ～80–87 km of the Southern Hemisphere (SH) to be up to 7.5 K warmer than its Northern Hemisphere (NH) counterpart. We show that this is consistent with our observation of asymmetries in the characteristics of PMSE and demonstrate how the mesosphere meridional wind field influences the existence and strength of the echoes in both hemispheres.  相似文献   

14.
Comparisons are drawn between certain middle atmosphere dynamical processes in the Southern Hemisphere and the Northern Hemisphere. Attention is focused on the zonal-mean climatological state, stationary waves, transient waves of various types, stratospheric sudden warmings and polar ozone minima. Observations of the similarities and differences between the hemispheres are mentioned, and ways in which these comparisons may be used to enhance our dynamical knowledge of the whole middle atmosphere are discussed.  相似文献   

15.
Global electron content (GEC) as a new ionospheric parameter was first proposed by Afraimovich et al. [2006]. GEC is equal to the total number of electrons in the near-Earth space. GEC better than local parameters reflects the global response to a change in solar activity. It has been indicated that, during solar cycle 23, the GEC dynamics followed similar variations in the solar UV irradiance and F 10.7 index, including the 11-year cycle and 27-day variations. The dynamics of the regional electron content (REC) has been considered for three belts: the equatorial belt and two midlatitude belts in the Northern and Southern hemispheres (±30° and 30°–65° geomagnetic latitudes, respectively). In contrast to GEC, the annual REC component is clearly defined for the northern and southern midlatitude belts; the REC amplitude is comparable with the amplitude of the seasonal variations in the Northern Hemisphere and exceeds this amplitude in the Southern Hemisphere by a factor of ～1.7. The dayside to nightside REC ratio, R(t), at the equator is a factor of 1.5 as low as such a GEC ratio, which indicates that the degree of nighttime ionization is higher, especially during the solar activity maximum. The pronounced annual cycle with the maximal R(t) value near 8.0 for the winter Southern Hemisphere and summer Northern Hemisphere is typical of midlatitudes.  相似文献   

16.
The results of an analysis of the spatial-temporal variations in the tropospheric temperature regime in the Northern and Southern hemispheres in 1948–2006 are presented. The possible effect of solar activity on the tropospheric temperature regime is discussed in the scope of the proposed mechanism by which the heliogeophysical factors affect the climatic characteristics and atmospheric circulation in the high-latitude troposphere through atmospheric electricity.  相似文献   

17.
基于AE8电子辐射带模式和各地磁场模式,本文系统分析了地磁场模式、太阳风、地磁扰动、地磁轴指向对静止轨道≥2 MeV高能电子分布的影响以及静止轨道不同经度位置≥2 MeV高能电子分布的差异,并与GOES系列卫星实测结果进行了对比分析.结果表明,AE8+IGRF+T96模式所得静止轨道≥2 MeV高能电子分布结果优于AE8+IGRF+OPQ77模式或AE8+IGRF+T89模式结果,其大部分定性结果与GOES系列卫星观测结果较为一致,AE8+IGRF+T96模式所得静止轨道≥2 MeV高能电子分布与磁壳参量Lm、局地磁场B分别呈较好的负和正相关性.基于AE8+IGRF+T96模式得到在相同太阳风及地磁扰动条件下2010年每分钟静止轨道≥2 MeV高能电子通量分布结果,经分析得到：1年内每个时刻静止轨道上≥2 MeV高能电子通量最大值和最小值比值变化范围为2.50~7.51,变化主周期为1天,每天比值变化量都超过3;1年内静止轨道各经度位置每天内≥2 MeV高能电子通量最大值和最小值比值变化范围为2.98~6.00,比值随着时间和经度位置而变化;1年内同一天静止轨道各经度位置≥2 MeV高能电子日积分通量最大值出现在170°W附近,最小值出现在70°W附近,最大值与最小值的比值分布在1.86~2.13之间.以上所得静止轨道≥2 MeV高能电子分布变化主要来自Lm变化,B/B0的影响小于5%,其中B0为磁力线上磁场最小值.因此,在构建≥2 MeV高能电子分布模式时,需要考虑地磁场结构的影响,特别是Lm参数.  相似文献   

18.
This study assesses the relation between the year-to-year variability of the semidiurnal tides (SDT) observed at high latitudes of both hemispheres and the global stratospheric stationary planetary wave (SPW) with zonal wavenumber S=1 (SPW1) derived from the UKMO temperature data. No significant positive correlation can be identified between the interannual variability of the Northern Hemisphere (NH) SDT and the Southern Hemisphere (SH) SPW1 for austral late-winter months. In contrast, a good consistency is evident for the interannual variations between the SDT observed at Rothera (68°S, 68°W) and the Arctic SPW1 for NH mid-winter months. Since it has been observed that during austral summer the non-migrating SDT often plays a significant role at the latitude of Rothera, a physical link between the SH SDT and the NH SPW is suggested. This asymmetry in the interhemispheric link is also noted in a recent study.  相似文献   

19.
The solar wind magnetic field distribution near the Earth has been studied and compared with the distribution anticipated according to the classical model. It has been indicated that a two-hump distribution of the IMF values discovered previously is not an artifact of averaging but reflects the actual structure of the magnetic field within the sector. In this case the magnetic field of polarity corresponding to the leading spot in the Northern Hemisphere is encountered more frequently. Not only the magnetic field magnitude but also the fields of either polarity increase with increasing activity. The distance between the peaks on the histogram of the magnetic field near the Earth increases from 6 to 10 nT. The quasi-22-year, 11-year, and quasibiennial (2.6 ± 0.3 years) cycles are observed in an alternate increase in the peaks, in the strength of the fields of either polarity, and in the ratio of the peaks to the occurrence frequency of zero values, respectively. The classical model is violated in approximately 25% of cases.  相似文献   

20.
Four years of SBUV ozone data and NOAA/NMC temperature data are analyzed for the relations between the annual total ozone behaviour in the Northern and Southern Hemispheres and the transport of ozone by planetary waves. It is found that the interhemispheric differences in the annual variation of total ozone are well explained by the interhemispheric differences in the planetary waves and the resulting ozone transports. The annual variation of the ozone transports by the stationary waves is found to control the ozone behavior in both hemispheres. Both the day-to-day and the interannual variation in total ozone are found to be strongly related to the corresponding variability of the planetary waves.Contribution Number 46 of the Stratospheric General Circulation with Chemistry Project at NASA/GSFC.  相似文献   

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