The Properties of Small Magnetic Regions on the Solar Surface and the Implications for the Solar Dynamo(s)

Hagenaar, H. J.; Schrijver, Carolus J.; Title, A. M.

doi:10.1086/345792

Cited by 187 publications

(248 citation statements)

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“…The global length scales of such magnetic complexes can be as large as 10 5 km, indicating that the associated flux ropes were formed in the main bulk of the convection zone (or at the bottom thereof) and have traversed it before appearing at the surface (Moreno-Insertis 1992, 1997. Going down from the largest scales, we find active regions in a continuum of sizes down to ephemeral active regions (Hagenaar et al 2003(Hagenaar et al , 2008. These appear at the center of meso-and supergranular cells; the two polarities of the region separate toward the boundaries of the cell, therefore reaching separations of order 10 4 km.…”

Section: Introductionmentioning

confidence: 79%

X-ray jets and magnetic flux emergence in the Sun

Moreno‐Insertis

2008

Proc. IAU

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Abstract. Magnetized plasma is emerging continually from the solar interior into the atmosphere. Magnetic flux emergence events and their consequences in the solar atmosphere are being observed with high space, time and spectral resolution by a large number of space missions in operation at present (e.g. SOHO, Hinode, Stereo, Rhessi). The collision of an emerging and a preexisting magnetic flux system in the solar atmosphere leads to the formation of current sheets and to field line reconnection. Reconnection under solar coronal conditions is an energetic event; for the field strengths, densities and speeds involved in the collision of emerging flux systems, the reconnection outflows lead to launching of high-speed (hundreds of km/s), high-temperature (10 7 K) plasma jets. Such jets are being observed with the X-Ray and EUV detectors of ongoing satellite missions. On the other hand, the spectacular increase in computational power in recent years permits to carry out three-dimensional numerical experiments of the time evolution of flux emerging systems and the launching of jets with a remarkable degree of detail.In this review, observation and modeling of the solar X-Ray jets are discussed. A two-decade long computational effort to model the magnetic flux emergence events by different teams has led to numerical experiments which explain, even quantitatively, many of the observed features of the X-ray jets. The review points out that, although alternative mechanisms must be considered, flux emergence is a prime candidate to explain the launching of the solar jets.

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Section: Introductionmentioning

confidence: 79%

X-ray jets and magnetic flux emergence in the Sun

Moreno‐Insertis

2008

Proc. IAU

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“…We assume that the magnetic fields in the photosphere are radial, and then the observed line-of-sight fields are corrected by cos(α) function, where α for each pixel is defined by its distance from solar disk center (Hagenaar et al 2003). We only analyze the pixels with angle α less than 60 • due to fewer and fewer magnetic signals with far away solar disk center, and set the flux density of those pixels with angle α lager than 60 • to zero.…”

Section: Observations and Data Analysismentioning

confidence: 99%

“…(1) No cyclic variations: Caii K emission in solar quiet regions (White & Livingston 1981); X-ray bright points (Hara & Nakakubo 2003); magnetic flux of networks (Labonte & Howard 1982); flux spectrum and total flux of network elements with flux 2.0 × 10 19 Mx (Hagenaar et al 2003); Stokes Q I profile (Trujillo Bueno et al 2004). (2) Anti-correlation of small-scale fields with sunspot cycle: number of network bright points in very quiet regions (Muller & Roudier 1984, 1994; Heii 10830Ådark points in the higher chromosphere (Harvey 1985); coronal X-ray bright points (Davis et al 1977;Davis 1983;Golub et al 1979;Sattarov et al 2002); weak changes of emergence frequency of ephemeral regions with flux less than (3-5)×10 19 Mx (Hagenaar et al 2003).…”

Section: Introductionmentioning

confidence: 99%

“…(2) Anti-correlation of small-scale fields with sunspot cycle: number of network bright points in very quiet regions (Muller & Roudier 1984, 1994; Heii 10830Ådark points in the higher chromosphere (Harvey 1985); coronal X-ray bright points (Davis et al 1977;Davis 1983;Golub et al 1979;Sattarov et al 2002); weak changes of emergence frequency of ephemeral regions with flux less than (3-5)×10 19 Mx (Hagenaar et al 2003).…”

Section: Introductionmentioning

confidence: 99%

“…Chunlan Jin & Jingxiu Wang (3) Correlation with sunspot cycle: more ephemeral regions appeared during active solar condition (Harvey & Harvey 1974;Harvey 1989); X-ray bright points (Golub et al 1979;Sattarov et al 2002Sattarov et al , 2010McIntosh & Gurman 2005); the number (or magnetic flux) of network structures (Foukal et al 1991;Meunier 2003); flux distribution and total flux of network concentrations with flux 3.0 × 10 19 Mx (Hagenaar et al 2003).…”

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confidence: 99%

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Magnetic network elements in solar cycle 23

Jin

Wang

2012

Proc. IAU

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Abstract. In this report, we present our recent effort to understand the cyclic behavior of network magnetic elements based on the unique database from full-disk observations provided by Michelson Doppler Imager on board the Solar and Heliospheric Observatory in the interval including the entire cycle 23. The following results are unclosed. (1) The quiet regions dominate the solar magnetic flux for about 8 years in solar cycle 23, and from the solar minimum to maximum they contribute (0.94-1.44)×10 23 Mx flux to the solar photosphere. In the entire cycle 23, the magnetic flux of the quiet regions is 1.12 times that of active regions. The occupation ratio of quiet region flux equally characterizes the course of a solar cycle. (2) With the increasing magnetic flux per element, the variations of numbers and total flux of the network elements show three-fold scenario: no-correlation, anti-correlation, and correlation with sunspots, respectively. The anti-correlated elements covering the range of (3-32)×10 18 Mx occupy 77% of total element number and 37% of quiet Sun flux. (3) The time-latitude distribution of anti-correlated magnetic elements is out of phase with that of sunspots, while the correlated elements display the similar butterfly diagram of sunspots but with wider latitude distribution. These results imply that the correlated elements are the debris of decayed sunspots, and the source of anti-correlated elements is modulated by sunspot magnetic field.

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Variation of the solar magnetic flux spectrum during solar cycle 23

Jin

Wang

2014

JGR Space Physics

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[1] By using the unique database of Solar and Heliospheric Observatory/Michelson Doppler Imager full disk magnetograms from September 1996 to January 2011, covering the entire solar cycle 23, we analyze the time-variability of the solar magnetic flux spectrum and study the properties of extended minimum of cycle 23. We totally identify 11.5 million magnetic structures. It has been revealed that magnetic features with different magnetic fluxes exhibit different cycle behaviors. The magnetic features with flux larger than 4.0 10 19 Mx, which cover solar active regions and strong network features, show exactly the same variation as sunspots; however, the remaining 82% magnetic features which cover the majority of network elements show anti-phase variation with sunspots. We select a criterion that the monthly sunspot number is less than 20 to represent the Sun's low activity status. Then we find the extended minimum of cycle 23 is characterized by the long duration of low activity status, but the magnitude of magnetic flux in this period is not lower than previous cycle. Both the duration of low activity status and the minimum activity level defined by minimum sunspot number show a century period approximately. The extended minimum of cycle 23 shows similarities with solar cycle 11, which preceded the mini-maxima in later solar cycles. This similarity is suggestive that the solar cycles following cycle 23 are likely to have low activity.

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The Properties of Small Magnetic Regions on the Solar Surface and the Implications for the Solar Dynamo(s)

Cited by 187 publications

References 22 publications

X-ray jets and magnetic flux emergence in the Sun

X-ray jets and magnetic flux emergence in the Sun

Magnetic network elements in solar cycle 23

Variation of the solar magnetic flux spectrum during solar cycle 23

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