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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We present an analytical diffusion-expansion Forbush decrease (FD) modelForbMod which is based on the widely used approach of the initially empty,closed magnetic structure (i.e. flux rope) which fills up slowly with particlesby perpendicular diffusion. The model is restricted to explain only thedepression caused by the magnetic structure of the interplanetary coronal massejection (ICME). We use remote CME observations and a 3D reconstruction method(the Graduated Cylindrical Shell method) to constrain initial boundaryconditions of the FD model and take into account CME evolutionary properties byincorporating flux rope expansion. Several flux rope expansion modes areconsidered, which can lead to different FD characteristics. In general, themodel is qualitatively in agreement with observations, whereas quantitativeagreement depends on the diffusion coefficient and the expansion properties(interplay of the diffusion and the expansion). A case study was performed toexplain the FD observed 2014 May 30. The observed FD was fitted quite well byForbMod for all expansion modes using only the diffusion coefficient as a freeparameter, where the diffusion parameter was found to correspond to expectedrange of values. Our study shows that in general the model is able to explainthe global properties of FD caused by FR and can thus be used to helpunderstand the underlying physics in case studies.

An Analytical Diffusion-Expansion Model for Forbush Decreases Caused by Flux Ropes