Formation of Ellerman bombs due to 3D flux emergence

Archontis, V.; Hood, A. W.

doi:10.1051/0004-6361/200912455

Cited by 103 publications

(123 citation statements)

References 35 publications

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“…The suggested domain is significantly hotter than the relative heating obtained by Archontis & Hood (2009) in their EB simulation. However, more recent MHD simulations of comparable reconnection phenomena show larger heating (Archontis & Hansteen 2014;Lee et al 2015), likely through magnetosonic wave excitation and dissipation (Longcope & Priest 2007).…”

Section: Discussionmentioning

confidence: 57%

“…Paper I showed that at high resolution upright flame morphology in limbward viewing is a distinctive EB characteristic. It was used in Paper II to establish EB brightness criteria, but these may fail close to disk center (Paper III) where differentiation with the MCs that produce EBs (as in the serpentine U-loop pull-up scenario of EB formation of e.g., Bernasconi et al 2002;Pariat et al 2004;Isobe et al 2007;Archontis & Hood 2009;Pariat et al 2009) is less easy, as already pointed out by Ellerman (1917) and later by Bruzek & Durrant (1977).…”

Section: Terminologymentioning

confidence: 99%

“…In addition to these ad-hoc Hα-synthesis attempts there have been numerical MHD simulations of EB reconnection by Archontis & Hood (2009), but without any spectral synthesis or verification, and by Nelson et al (2013) who probably did not emulate an EB nor observed one (Paper III).…”

Section: Introductionmentioning

confidence: 99%

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Hαfeatures with hot onsets

Rutten

2016

A&A

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Ellerman bombs are transient brightenings of the wings of the Balmer lines that uniquely mark reconnection in the solar photosphere.They are also bright in strong Ca ii and ultraviolet lines and in ultraviolet continua, but they are not visible in the optical continuum and the Na i D and Mg i b lines. These discordant visibilities invalidate all published Ellerman bomb modeling. I argue that the assumption of Saha-Boltzmann lower-level populations is informative to estimate bomb-onset opacities for these diverse diagnostics, even and especially for Hα, and employ such estimates to gauge the visibilities of Ellerman bomb onsets in all of them. They constrain Ellerman bomb formation to temperatures 10 000−20 000 K and hydrogen densities around 10 15 cm −3 . Similar arguments likely hold for Hα visibility in other transient phenomena with hot and dense onsets.

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Section: Discussionmentioning

confidence: 57%

Section: Terminologymentioning

confidence: 99%

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Hαfeatures with hot onsets

Rutten

2016

A&A

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“…The studied filament in this paper was existing for several rotations. MHD models show that the convection cells are different in flux emergence regions (Archontis & Török 2008;Archontis & Hood 2009). Future studies of the coupling between convection and filaments should be done during filament emergence.…”

Section: Conclusion and Discussionmentioning

confidence: 98%

Proper horizontal photospheric flows in a filament channel

Schmieder

Roudier

Mein

et al. 2014

A&A

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Context. An extended filament in the central part of the active region NOAA 11106 crossed the central meridian on Sept. 17, 2010 in the southern hemisphere. It has been observed in Hα with the THEMIS telescope in the Canary Islands and in 304 Å with the EUV imager (AIA) onboard the Solar Dynamic Observatory (SDO). Counterstreaming along the Hα threads and bright moving blobs (jets) along the 304 Å filament channel were observed during 10 h before the filament erupted at 17:03 UT. Aims. The aim of the paper is to understand the coupling between magnetic field and convection in filament channels and relate the horizontal photospheric motions to the activity of the filament.Methods. An analysis of the proper photospheric motions using SDO/HMI continuum images with the new version of the coherent structure tracking (CST) algorithm developed to track granules, as well as the large scale photospheric flows, was performed for three hours. Using corks, we derived the passive scalar points and produced a map of the cork distribution in the filament channel. Averaging the velocity vectors in the southern hemisphere in each latitude in steps of 3.5 arcsec, we defined a profile of the differential rotation. Results. Supergranules are clearly identified in the filament channel. Diverging flows inside the supergranules are similar in and out of the filament channel. Converging flows corresponding to the accumulation of corks are identified well around the Hα filament feet and at the edges of the EUV filament channel. At these convergence points, the horizontal photospheric velocity may reach 1 km s −1 , but with a mean velocity of 0.35 km s −1 . In some locations, horizontal flows crossing the channel are detected, indicating eventually large scale vorticity. Conclusions. The coupling between convection and magnetic field in the photosphere is relatively strong. The filament experienced the convection motions through its anchorage points with the photosphere, which are magnetized areas (ends, feet, lateral extensions of the EUV filament channel). From a large scale point-of-view, the differential rotation induced a shear of 0.1 km s −1 in the filament. From a small scale point-of-view, any convective motions favored the interaction of the parasitic polarities responsible for the anchorages of the filament to the photosphere with the surrounding network and may explain the activity of the filament.

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“…The HMI line forms in the middle of photosphere so we have only direct evidence for a photospheric flux cancellation. The magnetic reconnection scenario also has support from numerical modeling of resistive flux emergence in the solar surface (Archontis & Hood 2009). The magnetic field strength associated with the site of the EB in our data is comparable to the values reported by Socas-Navarro et al (2006) andBello González et al (2013) who reported a field strength on the order of the equipartition value.…”

Section: Magnetic Structure Of the Ebmentioning

confidence: 85%

Multiwavelength spectropolarimetric observations of an Ellerman bomb

Rezaei

Beck

2015

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Context. Ellerman bombs (EBs) are enhanced emission in the wings of the Hα line in the solar spectrum. Aims. We study the structure of an EB in the photosphere and chromosphere.Methods. We analyze simultaneous observations of four chromospheric lines (Hα, Ca ii H, Ca ii IR 854 nm, and He i 1083 nm) as well as two photospheric lines (Fe i 630 and Si i 1082.7 nm) along with high-cadence 160 and 170 nm ultraviolet (UV) continuum filtergrams. Full Stokes data from the Helioseismic and Magnetic Imager (HMI) are used to trace the temporal evolution of the magnetic structure.Results. We identify the EB by excess emission in the wings of the Hα line, a brightening in the UV continuum, and large emission peaks in the core of the two Ca ii lines. The EB shows a blueshift in all chromospheric lines, while no shifts are observed in the photospheric lines. The blueshift in the chromospheric layer causes very asymmetric emission peaks in the Ca ii H line. The photospheric Si i spectral line shows a shallower line depth at the location of the EB. The UV continuum maps show that the EB was substantially brighter than its surroundings for about 30 min. The continuum contrast of the EB from 170 nm to 1080 nm shows a power-law dependency on the wavelength. The temperature enhancement amounts to 130 K in the low photosphere and 400 K at the temperature minimum level. This temperature excess is also seen in an LTE inversion of the Ca ii spectra. The total thermal and radiative energy content of the EB is about 10 20 J and 10 18 J in the photosphere and chromosphere, respectively. The HMI data hints at a photospheric magnetic flux cancellation as the driver of the EB. Conclusions. Ellerman bombs release the energy in a height range of several pressure scale heights around the temperature minimum such that they affect both the photosphere and the lower chromosphere.

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Formation of Ellerman bombs due to 3D flux emergence

Cited by 103 publications

References 35 publications

Hαfeatures with hot onsets

Hαfeatures with hot onsets

Proper horizontal photospheric flows in a filament channel

Multiwavelength spectropolarimetric observations of an Ellerman bomb

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