Solar gamma-ray lines as probes of accelerated particle directionalities in flares

Anisotropies of charged particles accelerated in solar flares can be studied by observing Doppler shifts of selected $gamma$-ray lines. The spectral shape of the 6.1 MeV line of $sup 16$O has been calculated. If the accelerated particles are isotropic, the line remains centered at E$sub 0$=6129.4 keV, and its width (FWHM) is about 100 keV. However, for particle anisotropies that may be produced in solar flares, the line is shifted to lower energies by about 30 to 40 keV. (AIP)