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

The hard X-ray (HXR) emission in solar flares comes almost exclusively from avery small part of the flaring region, the footpoints of magnetic loops. UsingRHESSI observations of solar flare footpoints, we determine the radialpositions and sizes of footpoints as a function of energy in six near-limbevents to investigate the transport of flare accelerated electrons and theproperties of the chromosphere. HXR visibility forward fitting allows to findthe positions/heights and the sizes of HXR footpoints along and perpendicularto the magnetic field of the flaring loop at different energies in the HXRrange. We show that in half of the analyzed events, a clear trend of decreasingheight of the sources with energy is found. Assuming collisional thick-targettransport, HXR sources are located between 600 and 1200 km above thephotosphere for photon energies between 120 and 25 keV respectively. In theother events, the position as a function of energy is constant within theuncertainties. The vertical sizes (along the path of electron propagation)range from 1.3 to 8 arcseconds which is up to a factor 4 larger than predictedby the thick-target model even in events where the positions/heights of HXRsources are consistent with the collisional thick-target model. Magneticmirroring, collisional pitch angle scattering and X-ray albedo are discussed aspotential explanations of the findings.

Hard X-ray footpoint sizes and positions as diagnostics of flare accelerated energetic electrons in the low solar atmosphere