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

The large intensity of greater than 10 GeV positrons which apparently comefrom sources outside the Earth-Sun system observed recently by many spacecraft(PAMELA, FERMI, AMS2) is still a mystery with broad implications. In ourattempts to solve this mystery we have first tried to define reasonable limitsto the positrons produced in our own galaxy by nuclear interactions of cosmicrays. This is best done by using the secondary B/C ratio produced by these samecosmic rays in order to define the amount of matter traversed by galacticcosmic ray nuclei. Using new values of the B/C ratio together with earliercalculations of positron production by Moskalenko and Strong, 1998, we findthat at 10 GeV this galactic production is from 70% to almost 100% of thepositrons observed by the above experiments. At 100 GeV these fractions arestill from 20 to 33% of the positrons observed. The resulting excess positronspectrum above this normal galactic background is found to have an exponent-2.75, possibly flattening at lower energies. If these positrons are coming tous from a uniform source distribution in and beyond the disk of the galaxy witha source spectrum that is E-2.0, a spectral steepening caused by synchrotronand inverse Compton losses, which are largest near the galactic plane, willproduce a spectrum E-2.75 at the Earth. This is similar to the excess spectrumwe find. The excess positron spectrum E-2.75 that we obtain is also verysimilar to the positron spectrum produced by galactic protons in the Earthsatmosphere and in the spacecraft itself which also has a spectrum E-2.75. Thisresults in a background for all the above experiments. The assumption is thatthis type of background is removed by the stringent criteria that are imposedon each event. This calculation needs to be reconsidered before theimplications of these important positron results can be fully evaluated.

The Separation of Secondary Positrons Produced in the Galaxy from the  High Energy Positrons that are Observed Recent Space Experiments on PAMELA  and AMS2