Jing-Xiu Wang - Academia.edu (original) (raw)

Papers by Jing-Xiu Wang

The Astrophysical Journal

The poleward migration of the active regions’ magnetic flux on the solar surface plays an importa... more The poleward migration of the active regions’ magnetic flux on the solar surface plays an important role in the development of the large-scale field development, especially the polar-field reversal, which is a key process in the Babcock–Leighton-type solar dynamos. The poleward flux transport is nonuniform, centered around poleward surges as suggested by previous observations. The strong, long-lasting surges are related to activity complexes, and often result in violent polar-field reversal. However, the nonuniformity of poleward flux transport has not been evaluated quantitatively. We propose a statistical method to analyze the poleward flux transport during solar cycles 21–24 by considering the frequency distributions of the magnetic field at latitudes of poleward surges occurring during solar cycles. The nonuniformity is quantified as the kurtosis statistics representing the tailedness of the distributions. We test the method on results of surface flux transport simulations, and ...

Research in Astronomy and Astrophysics, 2019

This study aims at investigating surface magnetic flux participation among different types of mag... more This study aims at investigating surface magnetic flux participation among different types of magnetic features during solar cycle 24. State-of-the-art observations from SDO/HMI and Hinode/SOT are combined to form a unique database in the interval from April 2010 to October 2015. Unlike previous studies, the statistics presented in this paper are feature-detection-based. More than 20 million magnetic features with relatively large scale, such as sunspot/pore, enhanced and quiet networks, are automatically detected and categorized from HMI observations, and the internetwork features are identified from SOT/SP observations. The total flux from these magnetic features reaches 5.9×1022 Mx during solar minimum and 2.4×1023 Mx in solar maximum. Flux occupation from the sunspot/pore region is 29% in solar maximum. Enhanced and quiet networks contribute 18% and 21% flux during the solar minimum, and 50% and 9% flux in the solar maximum respectively. The internetwork field contributes over 5...

The Astrophysical Journal, 2019

The purpose of this paper is to show that large active regions (ARs) with different magnetic conf... more The purpose of this paper is to show that large active regions (ARs) with different magnetic configurations have different contributions to short-term and long-term variations of the Sun. As a case study, the complex δ-type AR 12673 and the simple β-type AR 12674 are investigated in detail. Since the axial dipole moment at cycle minimum determines the amplitude of the subsequent cycle and space climate, we have assimilated the individual observed magnetic configurations of these two ARs into a surface flux transport model to compare their contributions to the axial dipole moment D. We find that AR 12673 has a significant effect on D at the end of the cycle, making it weaker because of abnormal and complicated magnetic polarities. An initial strongly positive D ends up with a strongly negative value. The flare-poor AR 12674 has a greater contribution to the long-term axial dipole moment than the flare-rich AR 12673. We then carry out a statistical analysis of ARs larger than 800 μHem from 1976 to 2017. We use the flare index FI and define an axial dipole moment index DI to quantify the effects of each AR on space weather and space climate, respectively. Whereas the FI has a strong dependence on the magnetic configuration, the DI shows no such dependence. The DI is mainly determined by the latitudinal location and the latitudinal separation of the positive and negative magnetic fluxes of the ARs. Simple ARs have the same possibility as complex ARs to produce big DI values affecting space climate.

ABSTRACT The solar dynamo, which explains the origin and the evolution of all magnetic fields obs... more ABSTRACT The solar dynamo, which explains the origin and the evolution of all magnetic fields observed on the sun, is the fundamental and essential question of Solar Physics. Scientific inquiry into the question is more than an academic exercise. It is important to the development of space technology and the prediction of terrestrial climate. With the development of helioseismology, the solar dynamo has made great progresses. Staring from the observation, the paper summarizes some observations on the solar surface and the dynamic construction interior. The basic theories and the central models are introduced. Some unsolved problems are discussed.

Chinese Astronomy and Astrophysics, 1987

There are 4 types of evolution patterns of network magnetic fields: (1) flux cancellation, the mu... more There are 4 types of evolution patterns of network magnetic fields: (1) flux cancellation, the mutual disappearance of encountering fluxes of opposite polarity, (2) flux increase by emergence of ephemeral regions, (3) flux decrease of one polarity and (4) flux increase of one polarity, without emergence of ephemeral regions. From a time sequence of magnetograms of a quiet region of 1983 October 14, the evolution of 300 network features was measured. The magnetograms have a spatial resolution of 2 to 3 arcsec and a time resolution of about 2 hr. The statistics show that the contribution to flux decrease by Type 3 is 1.28 times that by Type 1, and the contribution to flux increase by Type 4 is 7 times that by Type 2.

Monthly Notices of the Royal Astronomical Society, 2007

Increasing observations are becoming available about a relatively weak, but persistent, non-axisy... more Increasing observations are becoming available about a relatively weak, but persistent, non-axisymmetric magnetic field co-existing with the dominant axisymmetric field on the Sun. It indicates that the non-axisymmetric magnetic field plays an important role in the origin of solar activity. A linear non-axisymmetric α 2 − Ω dynamo model is set up to discuss the characteristics of the axisymmetric (m = 0) and the first nonaxisymmetric (m = 1) modes and to provide further the theoretical bases to explain the 'active longitude', 'flip-flop' and other non-axisymmetric phenomena. The model consists of a updated solar internal differential rotation, a turbulent diffusivity varied with depth and an α-effect working at the tachocline in rotating spherical systems. The difference between the α 2 − Ω and the α − Ω models and the conditions to favor the non-axisymmetric modes with the solar-like parameters are also presented.

... irb. hr Vladimir Slemzin. PN Lebedev Physical Institute, Moscow, Russia slem@ sci. lebedev. r... more ... irb. hr Vladimir Slemzin. PN Lebedev Physical Institute, Moscow, Russia slem@ sci. lebedev. ru Sami Solanki, MPI fiir Sonnensystemforschung, Katlenburg-Lindau Germany solanki-orHceeUinmpi. mpg, de Wenbin Song, NAOC, Beijing, China wenbinQiourstar. bao. ac. ...

The Astrophysical Journal

Long-lasting activity complexes (ACs), characterized as a series of closely located, continuously... more Long-lasting activity complexes (ACs), characterized as a series of closely located, continuously emerging solar active regions (ARs), are considered generating prominent poleward surges from observations. The surges lead to significant variations of the polar field, which are important for the modulation of solar cycles. We aim to study a prominent poleward surge during solar cycle 24 on the southern hemisphere, and analyze its originating ACs and the effect on the polar field evolution. We automatically identify and characterize ARs based on synoptic magnetograms from the Solar Dynamics Observatory. We assimilate these ARs with realistic magnetic configuration into a surface flux transport model, and simulate the creation and migration of the surge. Our simulations well reproduce the characteristics of the surge and show that the prominent surge is mainly caused by the ARs belonging to two ACs during Carrington rotations 2145-2159 (2013 December-2015 January). The surge has a strong influence on the polar field evolution of the southern hemisphere during the latter half of cycle 24. Without the about one-year-long flux emergence in the form of ACs, the polar field around the cycle minimum would have remained at a low level and even reversed to the polarity at cycle 23 minimum. Our study also shows that the long-lived unipolar regions due to the decay of the earlier emerging ARs cause an intrinsic difficulty of automatically identifying and precisely quantifying later emerging ARs in ACs.

Astronomy & Astrophysics

Context. The solar dipole moment at cycle minimum is considered to be the most reliable precursor... more Context. The solar dipole moment at cycle minimum is considered to be the most reliable precursor with which to determine the amplitude of the subsequent cycle. Numerical simulations of the surface flux transport (SFT) model are widely used to effectively predict the dipole moment at cycle minimum. An algebraic method was recently proposed to quickly predict the contribution of an active region (AR) to the axial dipole moment at cycle minimum instead of SFT simulations. The method assumes a bipolar magnetic region (BMR) configuration of ARs, however most ARs are asymmetric in configuration of opposite polarities, or have more complex configurations. Such ARs evolve significantly differently from those of BMR approximations. Aims. We propose a generalized algebraic method to describe the axial dipole contribution of an AR with an arbitrary configuration, and evaluate its effectiveness compared to the BMR-based method. Methods. We employ mathematical deductions to obtain the generaliz...

The Astrophysical Journal

The prediction of the strength of future solar cycles is of interest because of its practical sig... more The prediction of the strength of future solar cycles is of interest because of its practical significance for space weather and as a test of our theoretical understanding of the solar cycle. The Babcock-Leighton mechanism allows predictions by assimilating the observed magnetic field on the surface. Since the emergence of sunspot groups has random properties, making it impossible to accurately predict the solar cycle and strongly limiting the scope of cycle predictions, we develop a scheme to investigate the predictability of the solar cycle over one cycle. When a cycle has been ongoing for more than three years, the sunspot group emergence can be predicted along with its uncertainty during the rest time of the cycle. The method for this prediction is to start by generating a set of random realizations that obey the statistical relations of the sunspot emergence. We then use a surface flux transport model to calculate the possible axial dipole moment evolutions. The correlation between the axial dipole moment at cycle minimum and the subsequent cycle strength and other empirical properties of solar cycles are used to predict the possible profiles of the subsequent cycle. We apply this scheme to predict the large-scale field evolution from 2018 to the end of cycle 25, whose maximum strength is expected to lie in the range from 93 to 155 with a probability of 95%.

Proceedings of the International Astronomical Union

Here we report our recent prediction of the solar cycle 25 based on a newly developed scheme, whi... more Here we report our recent prediction of the solar cycle 25 based on a newly developed scheme, which is used to investigate the predictability of the solar cycle over one cycle. The scheme is a combination of the empirical properties of solar cycles and a surface flux transport model to get the possible axial dipole moment evolution at a few years before cycle minimum, by which to get the subsequent cycle strength based on the correlation between the axial dipole moment at cycle minimum and the subsequent cycle strength. We apply this scheme to predict the large-scale field evolution since 2018 onwards. The results show that the northern polar field will keep on increasing, while the southern polar field almost keeps flat by the end of cycle 24. This leads to the cycle 25 strength of 125 ± 32, which is about 10% stronger than cycle 24 according to the mean value.

The Astrophysical Journal

The general solar-terrestrial effects including 20 parameters of major solar events in February, ... more The general solar-terrestrial effects including 20 parameters of major solar events in February, 1986 are analyzed and illustrated in terms of time sequence of various disturbances in interplanetary space, ionosphere and geomagnetic field. The characteristics of geomagnetic storm recorded at 6 stations are compared. The satellite anomaly and communication disturbance are also shown.

Active region 5229 was studied during 13 - 18 November 1988 using Hbeta filtergrams and Fe I 5324... more Active region 5229 was studied during 13 - 18 November 1988 using Hbeta filtergrams and Fe I 5324 videomagnetograms acquired at Huairou Solar Observing Station of Beijing Astronomical Observatory. Newly emerging flux, magnetic shear and magnetic flux cancellation were examined according to the evolution of magnetic fields. Preliminary results of the analysis were summarized.

Science, 2009

The origin of the solar wind in solar coronal holes has long been unclear. We establish that the ... more The origin of the solar wind in solar coronal holes has long been unclear. We establish that the solar wind starts flowing out of the corona at heights above the photosphere between 5 megameters and 20 megameters in magnetic fun- nels. This result is obtained by a correlation of the Doppler-velocity and radiance maps of spectral lines emitted by various

Chinese Astronomy and Astrophysics, 1986

An analysis of magneto-acoustic-gravity waves in the case of an isothermal atmosphere permeated b... more An analysis of magneto-acoustic-gravity waves in the case of an isothermal atmosphere permeated by a uniform magnetic field is presented. The general solution is expressed in terms of generalized hypergeometric functions. It can be used in numerical simulation of oscillations in a magnetic atmosphere. It is shown that the elliptically polarized magneto-acoustic-gravity waves consist of a pair of surface waves and a pair of body waves above the cut-off frequency. The body waves along the magnetic field are similar to acoustic waves in an atmosphere and their cut-off frequency is unaffected by magnetic field. The transverse oscillation decreases with height. For the usual boundary condition, the longitudinal oscillation decreases with height; however, in some cases, it may contain terms that increase with height. The solution is singular on a family of ellipses in the frequency - horizontal wave number plane. Near these ellipses, the wave components grow indefinitely.

Chinese Astronomy and Astrophysics, 1987

The Astrophysical Journal

Research in Astronomy and Astrophysics, 2019

The Astrophysical Journal, 2019

Chinese Astronomy and Astrophysics, 1987

Monthly Notices of the Royal Astronomical Society, 2007

The Astrophysical Journal

Astronomy & Astrophysics

The Astrophysical Journal

Proceedings of the International Astronomical Union

The Astrophysical Journal

Science, 2009

Chinese Astronomy and Astrophysics, 1986

Chinese Astronomy and Astrophysics, 1987