# Ellerman bomb

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In [solar physics](/source/Solar_physics), **Ellerman bombs** are intense, small-scale brightenings in the [Sun](/source/Sun)'s [photosphere](/source/Photosphere). They are only observed in the wings of the [Hα](/source/H%CE%B1), Hβ, and Hγ [hydrogen spectral lines](/source/Hydrogen_spectral_series) and take place in [emerging flux regions](/source/Emerging_flux_region) where emerging magnetic fields interact with existing fields. They are named after [Ferdinand Ellerman](/source/Ferdinand_Ellerman) who studied them in detail in the 20th century.

## History

Intense brightenings resembling what would later be referred to as Ellerman bombs were first reported by Walter M. Mitchell in 1909.[1] In 1917, observations of this phenomenon made at the [Mount Wilson Solar Observatory](/source/Mount_Wilson_Solar_Observatory) were described in detail by [Ferdinand Ellerman](/source/Ferdinand_Ellerman). He referred to them as "solar hydrogen bombs" in reference to the phenomenon only appearing in observations of hydrogen spectral lines.[2][3]

## Description

As originally described in Ellerman's 1917 paper, Ellerman bombs are intense brightenings in the wings of the [Hα](/source/H%CE%B1), Hβ, and Hγ [hydrogen spectral lines](/source/Hydrogen_spectral_series) with no brightening of the line cores or of other spectral lines.[2] They occur in [intergranular lanes](/source/Intergranular_lane) in the photosphere exclusively at the sites of [emerging flux regions](/source/Emerging_flux_region) where emerging vertical magnetic fields interact with the existing intergranular field. This interaction is suggested to result in [magnetic reconnection](/source/Magnetic_reconnection), producing the brightenings associated with Ellerman bombs.[4][5][6][7]

The lack of observed brightening of the Hα core is attributed to Ellerman bombs being a photospheric phenomenon. In growing active regions, dense chromospheric, Hα fibrils form a canopy above the photosphere blocking Hα emission from Ellerman bombs below. As a result, only emission in the Hα wings pass through and are observed.[4][6]

## References

1. Mitchell, Walter M. (September 1909). "Recent Solar Observations at Haverford". *The Astrophysical Journal*. **30**: 75. [Bibcode:1909ApJ....30...75M](https://ui.adsabs.harvard.edu/abs/1909ApJ....30...75M). [doi:10.1086/141687](https://doi.org/10.1086/141687)

1. Ellerman, Ferdinand (November 1917). "Solar Hydrogen 'bombs'". *The Astrophysical Journal*. **46**: 298. [Bibcode:1917ApJ....46..298E](https://ui.adsabs.harvard.edu/abs/1917ApJ....46..298E). [doi:10.1086/142366](https://doi.org/10.1086/142366)

1. Bhatnagar, A. & Livingston, William Charles (2005). [*Fundamentals of Solar Astronomy*](https://books.google.com/books?id=fe7XDuxCYjcC&pg=PA219). World Scientific. p. 219. ISBN 978-981-256-787-1.

1. Rutten, Robert J; Vissers, Gregal J M; Rouppe van der Voort, Luc H M; Sütterlin, Peter; Vitas, Nikola (11 June 2013). "Ellerman bombs: fallacies, fads, usage". *Journal of Physics: Conference Series*. **440** (1). [arXiv:1304.1364](https://arxiv.org/abs/1304.1364). [Bibcode:2013JPhCS.440a2007R](https://ui.adsabs.harvard.edu/abs/2013JPhCS.440a2007R). [doi:10.1088/1742-6596/440/1/012007](https://doi.org/10.1088/1742-6596/440/1/012007)

1. Libbrecht, Tine (2019). [*The diagnostic potential of the He I D3 spectral line in the solar atmosphere*](https://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-166996) (PhD). Stockholm University.

1. Watanabe, Hiroko; Vissers, Gregal; Kitai, Reizaburo; Rouppe van der Voort, Luc; Rutten, Robert J. (20 July 2011). "Ellerman Bombs at High Resolution. I. Morphological Evidence for Photospheric Reconnection". *The Astrophysical Journal*. **736** (1): 71. [arXiv:1105.4008](https://arxiv.org/abs/1105.4008). [Bibcode:2011ApJ...736...71W](https://ui.adsabs.harvard.edu/abs/2011ApJ...736...71W). [doi:10.1088/0004-637X/736/1/71](https://doi.org/10.1088/0004-637X/736/1/71)

1. Georgoulis, Manolis K.; Rust, David M.; Bernasconi, Pietro N.; Schmieder, Brigitte (10 August 2002). "Statistics, Morphology, and Energetics of Ellerman Bombs". *The Astrophysical Journal*. **575** (1): 506–528. [Bibcode:2002ApJ...575..506G](https://ui.adsabs.harvard.edu/abs/2002ApJ...575..506G). [doi:10.1086/341195](https://doi.org/10.1086/341195). [S2CID 818643](https://api.semanticscholar.org/CorpusID:818643)

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Adapted from the Wikipedia article [Ellerman bomb](https://en.wikipedia.org/wiki/Ellerman_bomb) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Ellerman_bomb?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.