Solar Activity Monitoring of Flares and CMEs Precursors: the Importance of Lyman-Alpha

Abstract : Events preceding the onset of a are are called 'precursors', and one of the prominent precursors is a newly emerging bipolar region at the surface, which may interact with pre-existing magnetic field in the corona and trigger a flare. Another well-known precursor is the activation, or eruption, of a filament that is composed of relatively cool plasma (around 10000 K), oated in the hot coronal plasma. Both emerging regions and filaments are well observed in Lyman-Alpha and H-Alpha and we expect that their combination might lead to a better identification of the changes at the origin of major flares and CMEs. The objective of the study we present, carried with the LYRA/PROBA-2 instrument (observations of early 2010) and H-Alpha observations (Hida Observatory), is to monitor flares in Lyman-Alpha and to compare sensitivity difference with H-Alpha to develop better precursor indicators on the flaring region. Comparison is also made with classical EUV { X-ray indicators (GOES 1-8 A but also LYRA channels 2- 3, Aluminum 17{80 nm, and 2-4, Zirconium 6{20 nm), showing that Lyman-Alpha flares are equally sensitive and detectable, with the advantage, though, of providing significant precursors. H-Alpha - although 1000 times less intense as a flare than Lyman-Alpha (exemple of C9.9 February 2010 are presented) - is indicative of the precursor elements to study. Many H- Alpha observations sources are available but we preferably use Peru or Hida Observatory data when available since providing velocities (spectroheliograms). This Lyman-Alpha flares and precursors study is pursued with recent observations campaigns with a spare Lyman detector of LYRA. But this interesting possibility to open and watch for flares from a promising region implies, accordingly, to rely on good precursors indications to limit filter's degradation. These observations are pointing the interest for future Lyman-Alpha irradiance measurements coupled, for precursors identification, to solar disk imaging.
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Contributor : Catherine Cardon <>
Submitted on : Friday, October 5, 2012 - 6:51:02 PM
Last modification on : Tuesday, May 14, 2019 - 11:04:05 AM

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  • HAL Id : hal-00739138, version 1

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Luc Damé, Safinaz Khaled, Satoru Ueno, Marie Dominique, Ingolf Dammasch, et al.. Solar Activity Monitoring of Flares and CMEs Precursors: the Importance of Lyman-Alpha. 39th COSPAR Scientific Assembly 2012, Jul 2012, Mysore, India. ⟨hal-00739138⟩

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