Topological Dissipation and the Small-Scale Fields in Turbulent Gases

Parker, E. N.

doi:10.1086/151512

Cited by 776 publications

(544 citation statements)

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“…This enhanced salt and pepper distribution of the magnetic field on small scales leads to a more complicated local field-line structure. The small scale convection allows for an additional energy input to the lower regions of the atmosphere through flux braiding (Parker 1972;Priest et al 2002) and, therefore, a higher transferee of energy into plasma heating through dissipation of current concentrations than can be inferred from our modelling. How this energy transfers into higher heights on the other hand is not clear, but it may be transferred further up in the atmosphere by MHD-waves, that may be dissipated by, for instance, phase mixing (Heyvaerts & Priest 1983) providing additional heating of the coronal domain, that may be important when including conduction and radiation in the model.…”

Section: Potential Field Modelmentioning

confidence: 88%

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Active region upflows

Galsgaard

Madjarska²,

Vanninathan

et al. 2015

A&A

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Context.Observations of many active regions show a slow systematic outflow/upflow from their edges lasting from hours to days. At present no physical explanation has been proven, while several suggestions have been put forward. Aims. This paper investigates one possible method for maintaining these upflows assuming, that convective motions drive the magnetic field to initiate them through magnetic reconnection. Methods. We use Helioseismic and Magnetic Imager (HMI) data to provide an initial potential 3D magnetic field of the active region NOAA 11123 on 2010 November 13 where the characteristic upflow velocities are observed. A simple 1D hydrostatic atmospheric model covering the region from the photosphere to the corona is derived. Local correlation tracking of the magnetic features in the HMI data is used to derive a proxy for the time dependent velocity field. The time dependent evolution of the system is solved using a resistive 3D magnetohydrodynamic code. Results. The magnetic field contains several null points located well above the photosphere, with their fan planes dividing the magnetic field into independent open and closed flux domains. The stressing of the interfaces between the different flux domains is expected to provide locations where magnetic reconnection can take place and drive systematic flows. In this case, the region between the closed and open flux is identified as the region where observations find the systematic upflows. Conclusions. In the present experiment, the driving only initiates magneto-acoustic waves without driving any systematic upflows at any of the flux interfaces.

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Section: Potential Field Modelmentioning

confidence: 88%

“…If inhomogeneities are present in the corona some of this energy may be tapped locally by phase-mixing (Heyvaerts & Priest 1983). This is a more realistic candidate to heat the corona in the open field regions than direct flux braiding (Parker 1972).…”

Section: Mhd Approachmentioning

confidence: 99%

Active region upflows

Galsgaard

Madjarska²,

Vanninathan

et al. 2015

A&A

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“…One group of theories proposes that velocities, produced by the internal convection and turbulent motions of the Sun, slowly (compared to the Alfvén speed) advect the footpoints of the coronal magnetic field on the solar surface, enabling energy to be stored in the magnetic field as current concentrations. In a series of papers by Parker (Parker 1972(Parker , 1979(Parker , 1994 it was proposed that the subsequent magnetic reconnection and dissipation of many current sheets (tangential discontinuities) in the solar atmosphere could lead to the observed coronal temperatures. Parker (1972) suggested that a uniform field that is subjected to highly complex velocity patterns at the footpoints, would lead to the creation of these current sheets and the subsequent energy dissipation.…”

Section: Introductionmentioning

confidence: 99%

Impact of flux distribution on elementary heating events

O'Hara

Moortel

2016

A&A

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Context. The complex magnetic field on the solar surface has been shown to contain a range of sizes and distributions of magnetic flux structures. The dynamic evolution of this magnetic carpet by photospheric flows provides a continual source of free magnetic energy into the solar atmosphere, which can subsequently be released by magnetic reconnection. Aims. We investigate how the distribution and number of magnetic flux sources impact the energy release and locations of heating through magnetic reconnection driven by slow footpoint motions. Methods. 3D magnetohydrodynamic (MHD) simulations using Lare3D are carried out, where flux tubes are formed between positive and negative sources placed symmetrically on the lower and upper boundaries of the domain, respectively. The flux tubes are subjected to rotational driving velocities on the boundaries and are forced to interact and reconnect. Results. Initially, simple flux distributions with two and four sources are compared. In both cases, central current concentrations are formed between the flux tubes and Ohmic heating occurs. The reconnection and subsequent energy release is delayed in the foursource case and is shown to produce more locations of heating, but with smaller magnitudes. Increasing the values of the background field between the flux tubes is shown to delay the onset of reconnection and increases the efficiency of heating in both the two-and four-source cases. The cases with two flux tubes are always more energetic than the corresponding four flux tube cases, however the addition of the background field makes this disparity less significant. A final experiment with a larger number of smaller flux sources is considered and the field evolution and energetics are shown to be remarkably similar to the two-source case, indicating the importance of the size and separation of the flux sources relative to the spatial scales of the velocity driver.

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“…These currents may be generated, for instance, through formation of tangential discontinuities due to photospheric footpoint motion (Parker 1972). The generation and dissipation of currents also can be expected above the reversals of the photospheric magnetic field observed below X-ray (Vaiana et al 1973) and extreme ultraviolet (EUV) solar coronal bright points (Habbal & Withbroe 1981).…”

Section: Introductionmentioning

confidence: 99%

On the role of current dissipation in the energization of coronal bright points

Adamson

Büchner

Otto

2013

A&A

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Aims. In the context of the contributions by DC dissipation to the energization of solar coronal X-ray and EUV bright points, we analyze the role of Joule heating in the formation of X-ray and EUV coronal bright points through current dissipation due to anomalous resistivity. Methods. We utilized the improved resistive MHD simulation code MPSCORONA3D, which allows for investigating resistive effects within the corona over a wide range of Reynolds numbers, starting from the nearly ideal Spitzer value of resistivity and including various models of current-carrier velocity dependent resistivity, arising from the consideration of turbulence in microscopic theory. Results. DC current dissipation contributes to the thermal energy increase in coronal bright point regions only under the assumption of an unrealistically low critical current-carrier velocity at which turbulent resistivity is switched on. For more realistic resistivity models, the corona is energized by plasma compression rather than by Joule heating due to the dissipation of direct currents. Conclusions. Joule heating within the solar corona depends critically on the magnitude of the resistivity.

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Topological Dissipation and the Small-Scale Fields in Turbulent Gases

Cited by 776 publications

References 0 publications

Active region upflows

Active region upflows

Impact of flux distribution on elementary heating events

On the role of current dissipation in the energization of coronal bright points

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