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تسجيل مستخدم جديدSun-as-a-Star Observation of Flares in Lyman {alpha} by the PROBA2/LYRA radiometer
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There are very few reports of flare signatures in the solar irradiance at H i Lyman {alpha} 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-{alpha} 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-{alpha} 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-{alpha} 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-{alpha} 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-{alpha} flare signal strong enough to appear in the solar irradiance.
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