Editing Van Allen radiation belt (section)

== Flux values ==
In the belts, at a given point, the flux of particles of a given energy decreases sharply with energy.

At the [[Magnetic dip|magnetic equator]], electrons of energies exceeding 5000&nbsp;keV (resp. 5&nbsp;MeV) have omnidirectional fluxes ranging from 1.2×10<sup>6</sup> (resp. 3.7×10<sup>4</sup>) up to 9.4×10<sup>9</sup> (resp. 2×10<sup>7</sup>) particles per square centimeter per second.

The proton belts contain protons with kinetic energies ranging from about 100&nbsp;keV, which can penetrate 0.6&nbsp;μm of [[lead]],  to over 400&nbsp;MeV, which can penetrate 143&nbsp;mm of lead.<ref>{{cite book |last=Hess |first=Wilmot N. |author-link=Wilmot N. Hess |title=The Radiation Belt and Magnetosphere |date=1968 |publisher=Blaisdell Pub. Co. |location=Waltham, MA |oclc=712421 |lccn=67019536|title-link=The Radiation Belt and Magnetosphere }}</ref>

Most published flux values for the inner and outer belts may not show the maximum probable flux densities that are possible in the belts. There is a reason for this discrepancy: the flux density and the location of the peak flux is variable, depending primarily on solar activity, and the number of spacecraft with instruments observing the belt in real time has been limited. The Earth has not yet experienced a solar storm of [[Solar storm of 1859|Carrington event]] intensity while spacecraft with the proper instruments have been available to observe the event.

Radiation levels in the belts would be dangerous to humans if they were exposed for an extended period of time. The Apollo missions minimised hazards for astronauts by sending spacecraft at high speeds through the thinner areas of the upper belts, bypassing inner belts completely, except for the Apollo 14 mission where the spacecraft traveled through the heart of the trapped radiation belts.<ref name="Goddard" /><ref>{{cite conference |title=Radiation Plan for the Apollo Lunar Mission |last1=Modisette |first1=Jerry L. |last2=Lopez |first2=Manuel D. |last3=Snyder |first3=Joseph W. |date=January 20–22, 1969 |conference=AIAA 7th Aerospace Sciences Meeting |location=New York |id=AIAA Paper No. 69-19 |doi=10.2514/6.1969-19 }}</ref><ref name="popsci.com">{{cite web|url=http://www.popsci.com/blog-network/vintage-space/apollo-rocketed-through-van-allen-belts|title=Apollo Rocketed Through the Van Allen Belts|date=7 January 2019}}</ref><ref>{{Cite web|url=https://www.hq.nasa.gov/alsj/a14/a14mr10.htm|title=Apollo 14 Mission Report, Chapter 10|website=www.hq.nasa.gov|access-date=2019-08-07}}</ref>

<gallery caption="Flux values, normal solar conditions" class="center" widths="300px" heights="240px">
File:Ap8-omni-0.100MeV.png|AP8 MIN omnidirectional proton flux ≥ 100 keV
File:Ap8-omni-1.000MeV.png|AP8 MIN omnidirectional proton flux ≥ 1 MeV
File:Ap8-omni-400.0MeV.png|AP8 MIN omnidirectional proton flux ≥ 400 MeV
</gallery>