English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present temporal variations of the Si IV line profiles at the flareribbons in three solar flares observed by the Interface Region ImagingSpectrograph (IRIS). In the M1.1 flare on 2014 September 6 and the X1.6 flareon 2014 September 10, the Si IV line profiles evolve from wholly redshifted tored-wing enhanced with the flare development. However, in the B1.8 flare on2016 December 2, the Si IV line profiles are wholly redshifted throughout theflare evolution. We fit the wholly redshifted line profiles with a singleGaussian function but the red-asymmetric ones with a double Gaussian functionto deduce the corresponding Doppler velocities. In addition, we find that hardX-ray emission above 25 keV shows up in the two large flares, implying anonthermal electron beam heating. In the microflare, there only appears weakhard X-ray emission up to 12 keV, indicative of a thermal heating mostly. Weinterpret the redshifts or red asymmetries of the Si IV line at the ribbons inthe three flares as spectral manifestations of chromospheric condensation. Wepropose that whether the line appears to be wholly redshifted or red-asymmetricdepends on the heating mechanisms and also on the propagation of thecondensation.

IRIS Si IV Line Profiles at Flare Ribbons as Indications of Chromospheric Condensation