Strong Blue Asymmetry in H α Line as a Preflare Activity

Document Type

Article

Publication Date

10-1-2016

Abstract

Chromospheric activities before solar flares provide important clues to the mechanisms that initiate solar flares, but are as yet poorly understood. We report a significant and rapid Hα line broadening before the solar flare SOL2011-09-29T18:08 that was detected using the unprecedented high-resolution Hα imaging spectroscopy with the Fast Imaging Solar Spectrograph (FISS) installed on the 1.6 m New Solar Telescope (NST) at Big Bear Solar Observatory. The strong Hα broadening extends as a blue excursion up to −4.5 Å and as a red excursion up to 2.0 Å, which implies a mixture of velocities in the range of −130kms−1 to 38 km s−1 derived by applying the cloud model, comparable to the highest chromospheric motions reported before. The Hα blueshifted broadening lasts for about six minutes and is temporally and spatially correlated with the start of a rising filament, which is later associated with the main phase of the flare as detected by the Atmosphere Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). The potential importance of this Hα blueshifted broadening as a preflare chromospheric activity is briefly discussed within the context of the two-step eruption model.

Identifier

84981502965 (Scopus)

Publication Title

Solar Physics

External Full Text Location

https://doi.org/10.1007/s11207-016-0963-5

e-ISSN

1573093X

ISSN

00380938

First Page

2391

Last Page

2406

Issue

8

Volume

291

Grant

21A20131111123

Fund Ref

Ministry of Education

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