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

In this work we study the kinematics of three small-scale (0.01 R$_\odot$)blobs of chromospheric plasma falling back to the Sun after the huge eruptiveevent of June 7, 2011. From a study of 3-D trajectories of blobs made with theSolar TErrestrial RElations Observatory (STEREO) data, we demonstrate theexistence of a significant drag force acting on the blobs and calculate twodrag coefficients, in the radial and tangential directions. The resulting dragcoefficients $C_D$ are between 0 and 5, comparable in the two directions,making the drag force only a factor of 0.45-0.75 smaller than the gravitationalforce. To obtain a correct determination of electron densities in the blobs, wealso demonstrate how, by combining measurements of total and polarizedbrightness, the H$\alpha$ contribution to the white-light emission observed bythe COR1 telescopes can be estimated. This component is significant forchromospheric plasma, being between 95 and 98 % of the total white-lightemission. Moreover, we demonstrate that the COR1 data can be employed even toestimate the H$\alpha$ polarized component, which turns out to be in the orderof a few percent of H$\alpha$ total emission from the blobs. If the drag forcesacting on small-scale blobs reported here are similar to those that play a roleduring the CME propagation, our results suggest that the magnetic drag shouldbe considered even in the CME initiation modelling.

Measurements with STEREO/COR1 data of drag forces acting on small-scale blobs falling in the intermediate corona