Skip to Main content Skip to Navigation
Journal articles

Sun-as-a-Star Observation of Flares in Lyman α by the PROBA2/LYRA Radiometer

Abstract : There are very few reports of flare signatures in the solar irradiance at H i Lyman α at 121.5 nm, i.e. the strongest line of the solar spectrum. The LYRA radiometer onboard PROBA2 has observed several flares for which unambiguous signatures have been found in its Lyman-α channel. Here we present a brief overview of these observations followed by a detailed study of one of them, the M2 flare that occurred on 8 February 2010. For this flare, the flux in the LYRA Lyman-α channel increased by 0.6%, which represents about twice the energy radiated in the GOES soft X-ray channel and is comparable with the energy radiated in the He ii line at 30.4 nm. The Lyman-α emission represents only a minor part of the total radiated energy of this flare, for which a white-light continuum was detected. Additionally, we found that the Lyman-α flare profile follows the gradual phase but peaks before other wavelengths. This M2 flare was very localized and has a very brief impulsive phase, but more statistics are needed to determine if these factors influence the presence of a Lyman-α flare signal strong enough to appear in the solar irradiance.
Document type :
Journal articles
Complete list of metadatas

Cited literature [23 references]  Display  Hide  Download
Contributor : Nathalie Pothier <>
Submitted on : Monday, January 18, 2016 - 3:39:21 PM
Last modification on : Wednesday, September 23, 2020 - 4:36:26 AM
Long-term archiving on: : Friday, November 11, 2016 - 9:56:20 AM


Files produced by the author(s)


Distributed under a Creative Commons Attribution - NonCommercial - NoDerivatives 4.0 International License




Matthieu Kretzschmar, M. Dominique, I. E. Dammasch. Sun-as-a-Star Observation of Flares in Lyman α by the PROBA2/LYRA Radiometer. Solar Physics, Springer Verlag, 2013, 286 (1), pp.221-239. ⟨10.1007/s11207-012-0175-6⟩. ⟨insu-01258050⟩



Record views


Files downloads