R

= 10 GR5 (n(H2)(2mp))2 Equating these and solving for B, we have B = (60 G)1/2 (2n(H2)mp R) = 6 X 10-5 gauss = 60 ^G

This is of the order of strengths of fields that have been measured from HI Zeeman measurements.

As a molecular cloud collapses, the magnetic field strength will increase, as illustrated in Fig. 15.5. This is because of the flux freezing, discussed in Chapter 11. (Remember, Faraday's law

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