Ensemble Empirical Mode Decomposition of the Magnetic Field of the Sun as a Star

NB, Xiang; Qu, Zhining

doi:10.3847/0004-6256/151/3/76

Cited by 33 publications

(17 citation statements)

References 39 publications

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“…The EMD (and EEMD, CEEMDAN) method does not require a priori assumption about the signal type, therefore it is widely and successfully used in the analysis of non-linear and non-stationary real-world signals, such as the variability of total solar irradiance (Li et al 2012;Lee et al 2015), the periodicity of flare index (Gao et al 2011), the research of solar mean magnetic field (Xiang & Qu 2016), the sunspot numbers (Barnhart & Eichinger 2011), etc (either EMD or EEMD is used in these studies). This method is more effective than the traditional Fourier analysis in extracting modes with time-variable amplitudes and timevarying frequencies in signals.…”

Section: Complete Ensemble Empirical Modementioning

confidence: 99%

Modulations of the surface magnetic field on the intra-cycle variability of total solar irradiance

Kong

2018

Astrophys Space Sci

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Solar photospheric magnetic field plays a dominant role in the variability of total solar irradiance (TSI). The modulation of magnetic flux at six specific ranges on TSI is characterized for the first time. The daily flux values of magnetic field at four ranges are extracted from MDI/SOHO, together with daily flux of active regions (MF ar ) and quiet regions (MF qr ); the first four ranges (MF 1−4 ) are: 1.5-2.9, 2.9-32.0, 32.0-42.7, and 42.7-380.1 (×10 18 Mx per element), respectively. Cross-correlograms show that MF 4 , MF qr , and MF ar are positively correlated with TSI, while MF 2 is negatively correlated with TSI; the correlations between MF 1 , MF 3 and TSI are insignificant. The bootstrapping tests confirm that the impact of MF 4 on TSI is more significant than that of MF ar and MF qr , and MF ar leads TSI by one rotational period. By extracting the rotational variations in the MFs and TSI, the modulations of the former on the latter at the solar rotational timescale are clearly illustrated and compared during solar maximum and minimum times, respectively. Comparison of the relative amplitudes of the long-term variation show that TSI is in good agreement with the variation of MF 4 and MF ar ; besides, MF 2 is in antiphase with TSI, and it lags the latter by about 1.5 years.

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Section: Complete Ensemble Empirical Modementioning

confidence: 99%

Modulations of the surface magnetic field on the intra-cycle variability of total solar irradiance

Kong

2018

Astrophys Space Sci

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“…Previous studies showed that there is a general consensus on ⋆ E-mail: fengwang@gzhu.edu.cn (FW) the magnitude and form of the interior rotation as inferred from helioseismology (Antia et al 1998), the surface differential rotation rate as derived from sunspots (Javaraiah 2013), Doppler velocity measurements (Snodgrass & Ulrich 1990), as well as the magnetic activity features (Komm et al 1993;Xiang & Qu 2016), but there is no such consensus regarding the rotation rule for the features in the solar corona, as pointed out by Hiremath & Hegde (2013). The main reasons why the coronal rotation is relatively less determined are as follows: i) there are virtually no obvious tracers, ii) the corona is the optically thin region, and iii) it is difficult to measure the coronal magnetic field (Vats et al 1998;Bhatt et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Systematic regularity of solar coronal rotation during the time interval 1939–2019

Deng

Zhang

Deng

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Temporal variation of the solar coronal rotation appears to be very complex and its relevances to the eleven-year solar activity cycle are still unclear. Using the modified coronal index for the time interval from 1939 January 1 to 2019 May 31, the systematic regularities of the solar coronal rotation are investigated. Our main findings are as follows: (1) from a global point of view, the synodic coronal rotation period with a value of 27.5 days is the only significant period at the periodic scales shorter than 64 days; (2) the coronal rotation period exhibit an obviously decreasing trend during the considered time interval, implying the solar corona accelerates its global rotation rate in the long run; (3) there exist significant periods of 3.25, 6.13, 9.53, and 11.13 years in the period length of the coronal rotation, providing an evidence that the coronal rotation should be connected with the quasi-biennial oscillation, the eleven-year solar cycle, and the 22-year Hale cycle (or the magnetic activity reversal); and (4) the phase relationship between the coronal rotation period and the solar magnetic activity is not only time-dependent but also frequency-dependent. For a small range around the 11-year cycle band, there is a systematic trend in the phase, and the small mismatch in this band brings out the phase to drift. The possible mechanism for the above analysis results is discussed.

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“…A huge amount of free magnetic energy stored in the solar atmosphere is released during their eruptions (Forbes 2000;Priest & Forbes 2002;Schmieder et al 2015). This energy is transformed into radiative energy, bulk kinetic energy, as well as thermal and nonthermal energy (Deng et al 2013;Lin et al 2015;Xiang & Qu 2016).…”

Section: Introductionmentioning

confidence: 99%

The Eruption of a Small-scale Emerging Flux Rope as the Driver of an M-class Flare and of a Coronal Mass Ejection

Yan

Jiang

Xue

et al. 2017

ApJ

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Solar flares and coronal mass ejections are the most powerful explosions in the Sun. They are major sources of potentially destructive space weather conditions. However, the possible causes of their initiation remain controversial. Using high-resolution data observed by the New Solar Telescope of Big Bear Solar Observaotry, supplemented by Solar Dynamics Observatory observations, we present unusual observations of a small-scale emerging flux rope near a large sunspot, whose eruption produced an M-class flare and a coronal mass ejection. The presence of the small-scale flux rope was indicated by static nonlinear force-free field extrapolation as well as data-driven magnetohydrodynamics modeling of the dynamic evolution of the coronal three-dimensional magnetic field. During the emergence of the flux rope, rotation of satellite sunspots at the footpoints of the flux rope was observed. Meanwhile, the Lorentz force, magnetic energy, vertical current, and transverse fields were increasing during this phase. The free energy from the magnetic flux emergence and twisting magnetic fields is sufficient to power the M-class flare. These observations present, for the first time, the complete process, from the emergence of the small-scale flux rope, to the production of solar eruptions.

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Ensemble Empirical Mode Decomposition of the Magnetic Field of the Sun as a Star

Cited by 33 publications

References 39 publications

Modulations of the surface magnetic field on the intra-cycle variability of total solar irradiance

Modulations of the surface magnetic field on the intra-cycle variability of total solar irradiance

Systematic regularity of solar coronal rotation during the time interval 1939–2019

The Eruption of a Small-scale Emerging Flux Rope as the Driver of an M-class Flare and of a Coronal Mass Ejection

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