Sustaining the Quiet Photospheric Network: The Balance of Flux Emergence, Fragmentation, Merging, and Cancellation

Schrijver, Carolus J.; Title, A. M.; Ballegooijen, A. A. van; Hagenaar, H. J.; Shine, R. A.

doi:10.1086/304581

Cited by 329 publications

(292 citation statements)

References 34 publications

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“…As shown for example by Schrijver et al (1997), the network magnetic cells consist of a large number of very small concentrations of mixed polarities, connected mostly via short loops. In such small structures, wave reflections or distortion can destroy the coherence between B and V fluctuations, not allowing the persistence of any phase difference.…”

Section: Velocity and Magnetic Field Correlationmentioning

confidence: 95%

Untitled

Cauzzi

Falchi

Falciani³

2001

Solar Physics

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Abstract. We analyze the temporal behavior of Network Bright Points (NBPs) searching for low-atmosphere signatures of flares occuring on the magnetic network. We make use of a set of data acquired during coordinated observations between ground based observatories (NSO/Sacramento Peak) and the MDI instrument onboard SOHO. Light curves in chromospheric spectral lines show only small amplitude temporal variations, without any sudden intensity enhancement that could suggest the presence of a transient phenomenon such as a (micro) flare. Only one NBP shows spikes of downward velocity, of the order of 2 -4 Km/s, considered as signals of compression associated to a (micro) flare occurrence. For this same NBP, we also find a peculiar relationship between the magnetic and velocity fields fluctuations, as measured by MDI. Only for this point the B -V fluctuations are well correlated, suggesting the presence of magneto-acoustic waves propagating along the magnetic structure. This correlation is lost during the compression episodes and resumes afterward. An A6 GOES soft X-ray burst is temporally associated with the downward velocity episodes, suggesting that this NBP is the footpoint of the flaring loop. This event has a total thermal energy content of about 10 28 erg, and hence belongs to the microflare class.

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Section: Velocity and Magnetic Field Correlationmentioning

confidence: 95%

Untitled

Cauzzi

Falchi

Falciani³

2001

Solar Physics

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“…(2) Understand Which Heating Mechanisms Dominate as a Function of Distance from the Sun Numerous models to describe the heating and acceleration mechanisms of the Hollweg (2008), Cranmer (2000), Hollweg and Isenberg (2002), Isenberg (2001a), Galinsky and Shevchenko (2000), Marsch and Tu (2001), Kasper et al (2008 b Matthaeus et al (1999), Dmitruk et al (2002), Cranmer et al (2007), Chandran et al (2009) c Bruner (1978), Ulmschneider (1985) d Parker (1979Parker ( , 1987, Sturrock (1999), Priest et al (2002), Axford and McKenzie (1992), Cargill and Klimchuk (2004), Schrijver et al (1997), Zurbuchen et al (2002) e Scudder (1994), Pierrard and Lamy (2003) solar corona and wind have been advanced with varying degrees of success, but none is universally accepted and possibly many are valid in some subset of plasma conditions. With the correct measurements SPP can determine the relative contribution of these mechanisms in the solar wind and understand which are most important.…”

Section: Heating the Corona And Solar Windmentioning

confidence: 99%

Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus

et al. 2015

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The Solar Wind Electrons Alphas and Protons (SWEAP) Investigation on SolarProbe Plus is a four sensor instrument suite that provides complete measurements of the electrons and ionized helium and hydrogen that constitute the bulk of solar wind and coronal plasma. SWEAP consists of the Solar Probe Cup (SPC) and the Solar Probe Analyzers (SPAN). SPC is a Faraday Cup that looks directly at the Sun and measures ion and electron fluxes and flow angles as a function of energy. SPAN consists of an ion and electron electrostatic analyzer (ESA) on the ram side of SPP (SPAN-A) and an electron ESA on the anti-ram side (SPAN-B). The SPAN-A ion ESA has a time of flight section that enables it to sort particles by their mass/charge ratio, permitting differentiation of ion species. SPAN-A and -B are rotated relative to one another so their broad fields of view combine like the seams on a baseball to view the entire sky except for the region obscured by the heat shield and covered by SPC. Observations by SPC and SPAN produce the combined field of view and measurement capabilities required to fulfill the science objectives of SWEAP and Solar Probe Plus. SWEAP measurements, in concert with magnetic and electric fields, energetic particles, and white light contextual imaging will enable discovery and understanding of solar wind acceleration and formation, coronal and solar wind heating, and particle acceleration in the inner heliosphere of the solar system. SPC and SPAN are managed by the SWEAP Electronics Module (SWEM), which distributes power, formats onboard data products, and serves as a single electrical interface to the spacecraft. SWEAP data products include ion and electron velocity distribution functions with high energy and angular resolution. Full resolution data are stored within the SWEM, enabling high resolution observations of structures such as shocks, reconnection events, and other transient structures to be selected for download after the fact. This paper describes the implementation of the SWEAP Investigation, the driving requirements for the suite, expected performance of the instruments, and planned data products, as of mission preliminary design review.

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“…The dynamics of the quiet Sun's upper atmosphere is driven by sub-surface convective motions that entrain small-scale magnetic flux concentrations and create a network of supergranular cells (Schrijver et al 1997;Parnell 2001;Priest et al 2002) outlined by bright chromospheric emission. The magnetic field appears to be crucial to the heating of the chromospheric network.…”

Section: Introductionmentioning

confidence: 99%

Relationship between supergranulation flows, magnetic cancellation and network flares

Attié

Innes

Solanki

et al. 2016

A&A

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Context. Photospheric flows create a network of often mixed-polarity magnetic field in the quiet Sun, where small-scale eruptions and network flares are commonly seen. Aims. The aim of this paper is (1) to describe the characteristics of the flows that lead to these energy releases, (2) to quantify the energy build up due to photospheric flows acting on the magnetic field, and (3) to assess its contribution to the energy of small-scale, short-lived X-ray flares in the quiet Sun. Methods. We used photospheric and X-ray data from the SoHO and Hinode spacecraft combined with tracking algorithms to analyse the evolution of five network flares. The energy of the X-ray emitting thermal plasma is compared with an estimate of the energy built up due to converging and sheared flux. Results. Quiet-Sun network flares occur above sites of converging opposite-polarity magnetic flux that are often found on the outskirts of network cell junctions, sometimes with observable vortex-like motion. In all studied flares the thermal energy was more than an order of magnitude higher than the magnetic free energy of the converging flux model. The energy in the sheared field was always higher than in the converging flux but still lower than the thermal energy. Conclusions. X-ray network flares occur at sites of magnetic energy dissipation. The energy is probably built up by supergranular flows causing systematic shearing of the magnetic field. This process appears more efficient near the junction of the network lanes. Since this work relies on 11 case studies, our results call for a follow-up statistical analysis to test our hypothesis throughout the quiet Sun.

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Sustaining the Quiet Photospheric Network: The Balance of Flux Emergence, Fragmentation, Merging, and Cancellation

Cited by 329 publications

References 34 publications

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Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus

Relationship between supergranulation flows, magnetic cancellation and network flares

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