GLOBAL SAUSAGE OSCILLATION of SOLAR FLARE LOOPS DETECTED by the INTERFACE REGION IMAGING SPECTROGRAPH

Document Type

Article

Publication Date

5-20-2016

Abstract

An observation from the Interface Region Imaging Spectrograph reveals coherent oscillations in the loops of an M1.6 flare on 2015 March 12. Both the intensity and Doppler shift of Fe xxi 1354.08 Å show clear oscillations with a period of ∼25 s. Remarkably similar oscillations were also detected in the soft X-ray flux recorded by the Geostationary Operational Environmental Satellites (GOES). With an estimated phase speed of ∼2420 km s-1 and a derived electron density of at least 5.4 × 1010 cm-3, the observed short-period oscillation is most likely the global fast sausage mode of a hot flare loop. We find a phase shift of ∼π/2 (1/4 period) between the Doppler shift oscillation and the intensity/GOES oscillations, which is consistent with a recent forward modeling study of the sausage mode. The observed oscillation requires a density contrast between the flare loop and coronal background of a factor ≥42. The estimated phase speed of the global mode provides a lower limit of the Alfvén speed outside the flare loop. We also find an increase of the oscillation period, which might be caused by the separation of the loop footpoints with time.

Identifier

84971576972 (Scopus)

Publication Title

Astrophysical Journal Letters

External Full Text Location

https://doi.org/10.3847/2041-8205/823/1/L16

e-ISSN

20418213

ISSN

20418205

Issue

1

Volume

823

Grant

NNG11PL10A

Fund Ref

National Aeronautics and Space Administration

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