Small scale solar magnetic fields and their relation to various solar activity indices

One of the most exciting developments in solar physics over the past eight years has been the success of ground based observers in resolving features with a scale smaller than the solar granulation. In particular, they have demonstrated the existence of intense magnetic fields, with strengths of up to about 1600G. Harvey (1976) has just given an excellent summary of these results.In solar physics, theory generally follows observations. Inter-granular magnetic fields had indeed been expected but their magnitude came as a surprise. Some problems have been discussed in previous reviews (Schmidt, 1968, 1974; Weiss, 1969; Parker, 1976d; Stenflo, 1976) and the new observations have stimulated a flurry of theoretical papers. This review will be limited to the principal problems raised by these filamentary magnetic fields. I shall discuss the interaction of magnetic fields with convection in the sun and attempt to answer such questions as: what is the nature of the equilibrium in a flux tube? how are the fields contained? what determines their stability? how are such strong fields formed and maintained? and what limits the maximum field strength?

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Solar activity indices as a proxy for the variation of ionospheric Total Electron Content (TEC) over Bahir Dar, Ethiopia during the year 2010–2014

Advances in Space Research ◽

10.1016/j.asr.2017.06.024 ◽

2017 ◽

Vol 60 (6) ◽

pp. 1237-1248

Author(s):

Tsegaye Kassa ◽

Samson Tilahun ◽

Baylie Damtie

Keyword(s):

Solar Activity ◽

Total Electron Content ◽

Electron Content ◽

Bahir Dar ◽

Total Electron ◽

Ionospheric Total Electron Content ◽

Solar Activity Indices ◽

Activity Indices

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Solar Activity Indices in the Cycles 21–23

The Sun: New Challenges - Astrophysics and Space Science Proceedings ◽

10.1007/978-3-642-29417-4_20 ◽

2012 ◽

pp. 221-228

Author(s):

A. A. Borisov ◽

E. A. Bruevich ◽

I. K. Rozgacheva ◽

G. V. Yakunina

Keyword(s):

Solar Activity ◽

Solar Activity Indices ◽

Activity Indices

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Small-Scale Solar Magnetic Fields

Symposium - International Astronomical Union ◽

10.1017/s0074180900008081 ◽

1976 ◽

Vol 71 ◽

pp. 69-99 ◽

Cited By ~ 7

Author(s):

J. O. Stenflo

Keyword(s):

Magnetic Fields ◽

Magnetic Flux ◽

Solar Surface ◽

Life Time ◽

Wave Number ◽

Small Scale ◽

Solar Magnetic Fields ◽

Field Amplification ◽

Wave Numbers ◽

Diffuse Form

The observed properties of small-scale solar magnetic fields are reviewed. Most of the magnetic flux in the photosphere is in the form of strong fields of about 100–200 mT (1–2 kG), which have remarkably similar properties regardless of whether they occur in active or quiet regions. These fields are associated with strong atmospheric heating. Flux concentrations decay at a rate of about 107 Wb s-1, independent of the amount of flux in the decaying structure. The decay occurs by smaller flux fragments breaking loose from the larger ones, i.e. a transfer of magnetic flux from smaller to larger Fourier wave numbers, into the wave-number regime where ohmic diffusion becomes significant. This takes place in a time-scale much shorter than the length of the solar cycle.The field amplification occurs mainly below the solar surface, since very little magnetic flux appears in diffuse form in the photosphere, and the life-time of the smallest flux elements is very short. The observations further suggest that most of the magnetic flux in quiet regions is supplied directly from below the solar surface rather than being the result of turbulent diffusion of active-region magnetic fields.

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Extended time series of Solar Activity Indices (ESAI): new possibilities for complex description of magnetic cycle

Proceedings of the International Astronomical Union ◽

10.1017/s1743921304006842 ◽

2004 ◽

Vol 2004 (IAUS223) ◽

pp. 555-556

Author(s):

Yu.A. Nagovitsyn ◽

V.G. Ivanov ◽

E.V. Miletsky ◽

D.M. Volobuev

Keyword(s):

Time Series ◽

Solar Activity ◽

Extended Time ◽

Magnetic Cycle ◽

Solar Activity Indices ◽

Activity Indices

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Global evolution of solar magnetic fields and prediction of activity cycles

Proceedings of the International Astronomical Union ◽

10.1017/s174392132000071x ◽

2019 ◽

Vol 15 (S354) ◽

pp. 147-156

Author(s):

Irina N. Kitiashvili

Keyword(s):

Solar Activity ◽

Magnetic Fields ◽

Activity Cycle ◽

Dynamo Model ◽

Solar Magnetic Fields ◽

Solar Cycles ◽

Multiscale Dynamics ◽

Activity Cycles ◽

Solar Dynamics ◽

Solar Activity Cycles

AbstractPrediction of solar activity cycles is challenging because physical processes inside the Sun involve a broad range of multiscale dynamics that no model can reproduce and because the available observations are highly limited and cover mostly surface layers. Helioseismology makes it possible to probe solar dynamics in the convective zone, but variations in differential rotation and meridional circulation are currently available for only two solar activity cycles. It has been demonstrated that sunspot observations, which cover over 400 years, can be used to calibrate the Parker-Kleeorin-Ruzmaikin dynamo model, and that the Ensemble Kalman Filter (EnKF) method can be used to link the modeled magnetic fields to sunspot observations and make reliable predictions of a following activity cycle. However, for more accurate predictions, it is necessary to use actual observations of the solar magnetic fields, which are available only for the last four solar cycles. In this paper I briefly discuss the influence of the limited number of available observations on the accuracy of EnKF estimates of solar cycle parameters, the criteria to evaluate the predictions, and application of synoptic magnetograms to the prediction of solar activity.

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Phase analysis of solar activity indices using wavelet techniques

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318001266 ◽

2018 ◽

Vol 13 (S340) ◽

pp. 165-166

Author(s):

C. S. Seema ◽

P. R. Prince

Keyword(s):

Solar Activity ◽

Extreme Ultraviolet ◽

Low Frequency ◽

Phase Relationship ◽

Precise Knowledge ◽

Frequency Components ◽

Cross Wavelet Transform ◽

Solar Activity Indices ◽

Wavelet Techniques ◽

Activity Indices

AbstractA precise knowledge of solar extreme ultraviolet (EUV) irradiance is of great importance for better understanding of Earth′s ionosphere and thermosphere. The search for an ideal solar EUV proxy is vital since the ionospheric and thermospheric models are based on the solar proxies of EUV radiation. In this study, the phase asynchrony analysis of solar EUV data with other solar activity indices during solar cycle 23 is done. The cross-wavelet transform (XWT) technique is used to reveal the phase difference between the two time series of solar indices. Analysis reveals that the phase relationship between the indices is both time and frequency dependent. The solar indices F10.7 and Mg II core-to-wing index are found to be more synchronous with solar EUV data for low frequency components.

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