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1.
Solar filaments show the position of large-scale polarity-inversion lines and are used for the reconstruction of large-scale
solar magnetic field structure on the basis of Hα synoptic charts for the periods that magnetographic measurements are not
available. Sometimes crossing filaments are seen in Hα filtergrams. We analyze daily Hα filtergrams from the archive of Big
Bear Solar Observatory for the period of 1999 – 2003 to find crossing and interacting filaments. A number of examples are
presented and filament patterns are compared with photospheric magnetic field distributions. We have found that all crossing
filaments reveal quadrupolar magnetic configurations of the photospheric field and presume the presence of null points in
the corona. 相似文献
2.
Digitized synoptic charts of photospheric magnetic fields were analyzed for the past 4 incomplete solar activity cycles (1969–2000).
The zonal structure and cyclic evolution of large-scale solar magnetic fields were investigated using the calculated values
of the radial B
r, |B
r|, meridional B
θ, |B
θ|, and azimuthal B
φ, |B
φ| components of the solar magnetic field averaged over a Carrington rotation (CR). The time–latitude diagrams of all 6 parameters
and their correlation analysis clearly reveal a zonal structure and two types of the meridional poleward drift of magnetic
fields with the characteristic times of travel from the equator to the poles equal to ∼16–18 and ∼2–3 years. A conclusion
is made that we observe two different processes of reorganization of magnetic fields in the Sun that are related to generation
of magnetic fields and their subsequent redistribution in the process of emergence from the field generation region to the
solar surface. Redistribution is supposed to be caused by some external forces (presumably, by sub-surface plasma flows in
the convection zone). 相似文献
3.
The time variation and latitude dependence of the solar rotation are found using observational data on Hα filaments and compact
magnetic features with different polarities during solar activity cycles 20 and 21 (1966–1985). Statistical analysis of the
observational data shows that there is a north–south asymmetry in the rotation, both for the Hα filaments and for compact
magnetic features (structures) with negative and positive polarities. The N-S asymmetry in the differential rotation of the
Hα filaments and the compact magnetic features with both polarities shows up quite distinctly in solar activity cycles 20
and 21, but the asymmetry for the compact magnetic features with positive polarity is comparatively lower in cycle 21. The
confidence level is lower the compact magnetic features with positive polarity than for the compact magnetic features with
negative polarity. 相似文献
4.
A. V. Mordvinov 《Solar physics》2007,246(2):445-456
A comparative analysis of solar and heliospheric magnetic fields in terms of their cumulative sums reveals cyclic and long-term
changes that appear as a magnetic flux imbalance and alternations of dominant magnetic polarities. The global magnetic flux
imbalance of the Sun manifests itself in the solar mean magnetic field (SMMF) signal. The north – south asymmetry of solar
activity and the quadrupole mode of the solar magnetic field contribute the most to the observed magnetic flux imbalance.
The polarity asymmetry exhibits the Hale magnetic cycle in both the radial and azimuthal components of the interplanetary
magnetic field (IMF). Analysis of the cumulative sums of the IMF components clearly reveals cyclic changes in the IMF geometry.
The accumulated deviations in the IMF spiral angle from its nominal value also demonstrate long-term changes resulting from
a slow increase of the solar wind speed over 1965 – 2006. A predominance of the positive IMF B
z
with a significant linear trend in its cumulative signal is interpreted as a manifestation of the relic magnetic field of
the Sun. Long-term changes in the IMF B
z
are revealed. They demonstrate decadal changes owing to the 11/22-year solar cycle. Long-duration time intervals with a dominant
negative B
z
component were found in temporal patterns of the cumulative sum of the IMF B
z
. 相似文献
5.
Valentine I. Makarov 《Solar physics》1994,150(1-2):359-374
Properties of even and odd 11-year solar cycles as part of the 22-year magnetic cycle have been studied on the basis of the
data on the zonal structure of the large-scale magnetic field, of polar faculae activity cycles, duration of 11-year cycles,
high-latitude prominence areas, inclinations of the coronal streamers, velocity of magnetic neutral line migration, and peculiarities
of the polar magnetic field reversal. It is shown that the properties of the odd cycle depend on those of the preceding even
cycle. The 22-year magnetic cycle, consisting of an even and odd cycle, is a unified dynamic process. The new data obtained
show that the poloidal magnetic fieldB(p) of ‘+’ and ‘−’ polarity for the new 22-year magnetic cycle is formed simultaneously, possibly in deep layers of the Sun
in the form of a certain magnetic configuration, containing alternating ‘+’ and ‘−’ polarities of the field. 相似文献
6.
We outline a method to determine the direction of solar open flux transport that results from the opening of magnetic clouds
(MCs) by interchange reconnection at the Sun based solely on in-situ observations. This method uses established findings about i) the locations and magnetic polarities of emerging MC footpoints, ii) the hemispheric dependence of the helicity of MCs, and iii) the occurrence of interchange reconnection at the Sun being signaled by uni-directional suprathermal electrons inside MCs.
Combining those observational facts in a statistical analysis of MCs during solar cycle 23 (period 1995 – 2007), we show that
the time of disappearance of the northern polar coronal hole (1998 – 1999), permeated by an outward-pointing magnetic field,
is associated with a peak in the number of MCs originating from the northern hemisphere and connected to the Sun by outward-pointing
magnetic field lines. A similar peak is observed in the number of MCs originating from the southern hemisphere and connected
to the Sun by inward-pointing magnetic field lines. This pattern is interpreted as the result of interchange reconnection
occurring between MCs and the open field lines of nearby polar coronal holes. This reconnection process closes down polar
coronal hole open field lines and transports these open field lines equatorward, thus contributing to the global coronal magnetic
field reversal process. These results will be further constrainable with the rising phase of solar cycle 24. 相似文献
7.
Variations of solar differential rotation have been studied using observations of solar quiescent Hα filaments obtained during
1965–1993 at the Abastumani Astrophysical Observatory.
In both hemispheres of the Sun, propagation of a quasi-biennial pulse of residual rotation velocities of filaments was found.
There is a pulse drift from high latitudes to the equator in the northern hemisphere in 1968–1970, 1979–1981, 1988–1990 and
in the southern one in 1969–1971, 1979–1981, 1989–1991.
Propagation of a pulse starts near the time of the polarity reversal of the circumpolar regions of the Sun. High-latitude
double peaks of rapid motion were found in the northern hemisphere for cycle 20 and in the southern hemisphere for cycle 22.
The relation of the appearance of suggested double pulse peaks of residual velocities with the threefold polarity changing
of the circumpolar areas is suggested. 相似文献
8.
Kenneth H. Schatten 《Solar physics》2009,255(1):3-38
Photospheric ephemeral regions (EPRs) cover the Sun like a magnetic carpet. From this, we update the Babcock – Leighton solar
dynamo. Rather than sunspot fields appearing in the photosphere de novo from eruptions originating in the deep interior, we consider that sunspots form directly in the photosphere by a rapid accumulation
of like-sign field from EPRs. This would only occur during special circumstances: locations and times when the temperature
structure is highly superadiabatic and contains a large subsurface horizontal magnetic field (only present in the Sun’s lower
latitudes). When these conditions are met, superadiabatic percolation occurs, wherein an inflow and downflow of gas scours
the surface of EPRs to form active regions. When these conditions are not met, magnetic elements undergo normal percolation,
wherein magnetic elements move about the photosphere in Brownian-type motions. Cellular automata (CA) models are developed
that allow these processes to be calculated and thereby both small-scale and large-scale models of magnetic motions can be
obtained. The small-scale model is compared with active region development and Hinode observations. The large-scale CA model offers a solar dynamo, which suggests that fields from decaying bipolar magnetic regions
(BMRs) drift on the photosphere driven by subsurface magnetic forces. These models are related to observations and are shown
to support Waldmeier’s findings of an inverse relationship between solar cycle length and cycle size. Evidence for significant
amounts of deep magnetic activity could disprove the model presented here, but recent helioseismic observations of “butterfly
patterns” at depth are likely just a reflection of surface activity. Their existence seems to support the contention made
here that the field and flow separate, allowing cool, relatively field-free downdrafts to descend with little field into the
nether worlds of the solar interior. There they heat by compression to form a hot solar-type Santa Ana wind deep below active
regions. 相似文献
9.
Measurement of the floor in the interplanetary magnetic field and estimation of the time-invariant open magnetic flux of the
Sun require knowledge of closed magnetic flux carried away by coronal mass ejections (CMEs). In contrast with previous papers,
we do not use global solar parameters to estimate such values: instead we identify different large-scale types of solar wind
for the 1976 – 2000 interval to obtain the fraction of interplanetary CMEs (ICMEs). By calculating the magnitude of the interplanetary
magnetic field B averaged over two Carrington rotations, the floor of the magnetic field can be estimated from the B value at a solar cycle minimum when the number of ICMEs is minimal. We find a value of 4.65±0.6 nT, in good agreement with
previous results. 相似文献
10.
Magnetic reconnection in the temperature minimum region of the solar photosphere can account for the canceling magnetic features
on the Sun. Litvinenko (1999a) showed that a reconnection model explains the quiet-Sun features with the magnetic flux cancelation
rate of order 1017 Mx hr−1. In this paper the model is applied to cancelation in solar active regions, which is characterized by a much larger rate
of cancelation ∖ ge1019 Mx hr−1. In particular, the evolution of a photospheric canceling feature observed in an active region on July 2, 1994 is studied.
The theoretical predictions are demonstrated to be in reasonable agreement with the measured speed of approaching magnetic
fragments, the magnetic field in the fragments, and the flux cancelation rate, deduced from the combined Big Bear Hα time-lapse
images and videomagnetograms calibrated against the daily NSO/Kitt Peak magnetogram. Of particular interest is the prediction
that photospheric reconnection should lead to a significant upward mass flux and the formation of a solar filament. Hα observations
indeed showed a filament that had one of its ends spatially superposed with the canceling feature.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1005284116353 相似文献
11.
The differential rotation of compact magnetic elements during activity cycles 20 and 21 (1966 – 1986) is studied by using
solar synoptic charts. For each hemisphere the compact magnetic elements with the polarity of the circumpolar magnetic field
have larger rotation rates than the elements with the opposite polarity. This difference in rotation rates is present during
the whole cycle except during the polarity reversal of the circumpolar field. 相似文献
12.
The large-scale structure of the solar magnetic field during the past five sunspot cycles (representing by implication a much longer interval of time) has been investigated using the polarity (toward or away from the Sun) of the interplanetary magnetic field as inferred from polar geomagnetic observations. The polarity of the interplanetary magnetic field has previously been shown to be closely related to the polarity (into or out of the Sun) of the large-scale solar magnetic field. It appears that a solar structure with four sectors per rotation persisted through the past five sunspot cycles with a synodic rotation period near 27.0 days, and a small relative westward drift during the first half of each sunspot cycle and a relative eastward drift during the second half of each cycle. Superposed on this four-sector structure there is another structure with inward field polarity, a width in solar longitude of about 100° and a synodic rotation period of about 28 to 29 days. This 28.5 day structure is usually most prominent during a few years near sunspot maximum. Some preliminary comparisons of these observed solar structures with theoretical considerations are given. 相似文献
13.
The global distribution of solar surface activity (active regions) is apparently connected with processes in the convection
zone. The large-scale magnetic structures above the tachocline could in a pronounced way be observable in the surface magnetic
field. To get the information regarding large-scale magnetic formations in the convection zone, a set of solar synoptic charts
(Mount Wilson 1998 – 2004, Fe i, 525.02 nm) have been analyzed. It is shown that the longitudinal dimensions and dynamics of supergiant complexes of solar
surface activity carry valuable information about the processes in the convection zone of the Sun. A clear effect of large-scale
(global) turbulence is found. This is a ‘fingerprint’ of deep convection, because there are no such large-scale turbulent
eddies in the solar photosphere. The preferred scales of longitudinal variations in surface solar activity are revealed. These
are: ∼ 24° (gigantic convection cells), 90°, 180° and 360°. 相似文献
14.
Magnetic field structures of Hα flares associated with meter-wave type III bursts during periods of low solar activity in
1975 – 1977 and 1985 – 1987 were investigated. In a statistical analysis it was confirmed that the association rate depends
less on flare importance than on brightness. For subflares (95% of the sample), the location of the Hα flare in the bipolar
pattern turned out to be crucial for the association rate. It is almost one order of magnitude larger for flares occurring
at the border of the active regions, compared to flares located inside the general bipolar pattern. For selected typical examples
of flares, extrapolations of the measured magnetic fields were performed. By matching Hα filtergrams and calculated 3-D structures
it was found that the positions at the border where the flares associated with type III bursts occurred were close to open
field lines extending into the corona. In most investigated cases intrusions of parasitic polarity were found in the vicinity
of the flare locations. The extrapolations showed that subflares located inside the bipolar pattern but have not been associated
with type III bursts were covered by dense arcades of magnetic loops. 相似文献
15.
Yu Liu 《Solar physics》2008,249(1):75-84
Liu et al. (Astrophys. J.
628, 1056, 2005a) described one surge – coronal mass ejection (CME) event showing a close relationship between solar chromospheric surge ejection
and CME that had not been noted before. In this work, large Hα surges (>72 Mm, or 100 arcsec) are studied. Eight of these
were associated with CMEs. According to their distinct morphological features, Hα surges can be classified into three types:
jetlike, diffuse, and closed loop. It was found that all of the jetlike surges were associated with jetlike CMEs (with angular
widths ≤30 degrees); the diffuse surges were all associated with wide-angle CMEs (e.g., halo); the closed-loop surges were not associated with CMEs. The exclusive relation between Hα surges and CMEs indicates
difference in magnetic field configurations. The jetlike surges and related narrow CMEs propagate along coronal fields that
are originally open. The unusual transverse mass motions in the diffuse surges are suggested to be due to magnetic reconnections
in the corona that produce wide-angle CMEs. For the closed-loop surges, their paths are just outlining stable closed loops
close to the solar surface. Thus no CMEs are associated with them. 相似文献
16.
J. H. Piddington 《Solar physics》1972,22(1):3-19
The dynamo theory of the solar cycle as developed by Parker and others, and the observational models of Babcock and Leighton have been examined, with the conclusion that the dynamo theory is not applicable to the Sun and that the models fail.An essential part of the theory is an adequate effective diffusion coefficient. Fields are continuously sheared and amplified and, in this theory, these may not be allowed to accumulate; all subsurface fields of an old cycle must be eliminated. Ohmic diffusion is negligible and turbulent diffusion is invoked. However, this requires that all solar fields are tangled to a small scale, which is contrary to observation; for Hale's polarity laws are strictly observed, and large-scale surface features are common at the end of an 11-yr cycle in the same general area where new fields are appearing.The erupted (sunspot) fields lie generally above the unerupted, toroidal fields so that, even if they are merged as required, the centroid of the new system would be above that of the old. The result is not a steady-state oscillator, as required, but the complete loss of the solar field.It is concluded that for these and other reasons a shallow, reversing field is unacceptable, and that a deeply penetrating field is required. Reference is made to an alternative theory of the solar cycle based on a deep magnetic field. 相似文献
17.
The evolution of the large-scale magnetic field of the Sun has been studied using an algorithm of tomographic inversion. By analyzing line-of-sight magnetograms, we mapped the radial and toroidal components of the Sun??s large-scale magnetic field. The evolution of the radial and toroidal magnetic field components in the 11-year solar cycle has been studied in a time?Clatitude aspect. It is shown that the toroidal magnetic field of the Sun is causally related to sunspot activity; i.e., the sunspot formation zones drift in latitude and follow the toroidal magnetic fields. The results of our analysis support the idea that the high-latitude toroidal magnetic fields can serve as precursors of sunspot activity. The toroidal fields in the current cycle are anomalously weak and also show a barely noticeable equatorward drift. This behavior of the toroidal magnetic field suggests low activity levels in the current cycle and in the foreseeable future. 相似文献
18.
Extreme-ultraviolet data from EIT/SOHO (1996–2002), soft X-ray data from Yohkoh (1991–2001), and magnetic field data from MDI/SOHO (1996–2002) and Kitt Peak Observatory, NSO/NOAO (1991–2002) are analyzed
together in the form of synoptic maps for the investigation of solar cycle variations of the corona and their relation to
the magnetic field. These results show new interesting relations between the evolution of the topological structure of the
corona, coronal heating and the large-scale magnetic field. The long-lived coronal structures are related to complexes of
solar activity and display quasi-periodic behavior (in the form of impulses of coronal activity) with periods of 1.0–1.5 year,
in the axisymmetric distribution of EUV and X-ray fluxes during the current solar cycle 23. In particular, during the second
maximum of this cycle the solar corona became somewhat hotter than it was in the period of the first maximum. 相似文献
19.
Y.-M. Wang 《Solar physics》2004,224(1-2):21-35
The Sun’s large-scale external field is formed through the emergence of magnetic flux in active regions and its subsequent
dispersal over the solar surface by differential rotation, supergranular convection, and meridional flow. The observed evolution
of the polar fields and open flux (or interplanetary field) during recent solar cycles can be reproduced by assuming a supergranular
diffusion rate of 500 – 600 km2 s−1 and a poleward flow speed of 10 –20 m s−1. The nonaxisymmetric component of the large-scale field decays on the flow timescale of ∼1 yr and must be continually regenerated
by new sunspot activity. Stochastic fluctuations in the longitudinal distribution of active regions can produce large peaks
in the Sun’s equatorial dipole moment and in the interplanetary field strength during the declining phase of the cycle; by
the same token, they can lead to sudden weakenings of the large-scale field near sunspot maximum (Gnevyshev gaps). Flux transport
simulations over many solar cycles suggest that the meridional flow speed is correlated with cycle amplitude, with the flow
being slower during less active cycles. 相似文献
20.
We have defined the duration of polar magnetic activity as the time interval between two successive polar reversals. The epochs of the polarity reversals of the magnetic field at the poles of the Sun have been determined (1) by the time of the final disappearance of the polar crown filaments and (2) by the time between the two neighbouring reversals of the magnetic dipole configuration (l=1) from the H synoptic charts covering the period 1870–2001. It is shown that the reversals for the magnetic dipole configuration (l=1) occur on an average 3.3±0.5 years after the sunspot minimum according to the H synoptic charts (Table I) and the Stanford magnetograms (Table III). If we set the time of the final disappearance of the polar crown filaments (determined from the latitude migration of filaments) as the criterion for deciding the epoch of the polarity reversal of the polar fields, then the reversal occurs on an average 5.8±0.6 years from sunspot minimum (last column of Table I). We consider this as the most reliable diagnostic for fixing the epoch of reversals, as the final disappearance of the polar crown filaments can be observed without ambiguity. We show that shorter the duration of the polar activity cycle (i.e., the shorter the duration between two neighbouring reversals), the more intense is the next sunspot cycle. We also notice that the duration of polar activity is always more in even solar cycles than in odd cycles whereas the maximum Wolf numbers W
\max is always higher for odd solar cycles than for even cycles. Furthermore, we assume there is a secular change in the duration of the polar cycle. It has decreased by 1.2 times during the last 120 years. 相似文献