number of particles crossing a sphere of unit cross-sectional area (i.e. of radius 1/ ) per unit time


  • NOTE 1 For arbitrary angular distributions, it is normally known as omnidirectional flux.
  • NOTE 2 Flux is often expressed in 'integral form' as particles per unit time (e.g. electrons cm-2 s-1) above a certain energy threshold.
  • NOTE 3 The directional flux is the differential with respect to solid angle (e.g. particles-cm-2steradian-1s-1) while the 'differential' flux is is differential with respect to energy (e.g. particles-cm-2MeV-1s-1). In some cases fluxes are treated as a differential with respect to linear energy transfer rather than energy.


Glossary app image

ECSS Glossary mobile applications

ECSS Glossary mobile apps available from iOS and Android store and ECSS Glossary Plugin for MS Word available from Microsoft Appstore
Search the online Glossary