  The angular distribution of electrons accelerated in solar flares is a key
parameter in the understanding of the acceleration and propagation mechanisms
that occur there. However, the anisotropy of energetic electrons is still a
poorly known quantity, with observational studies producing evidence for an
isotropic distribution and theoretical models mainly considering the strongly
beamed case. We use the effect of photospheric albedo to infer the pitch angle
distribution of X-ray emitting electrons using Hard X-ray data from RHESSI. A
bi-directional approximation is applied and a regularized inversion is
performed for eight large flare events to deduce the electron spectra in both
downward (towards the photosphere) and upward (away from the photosphere)
directions. The electron spectra and the electron anisotropy ratios are
calculated for broad energy range from about 10 and up to ~ 300 keV near the
peak of the flares. The variation of electron anisotropy over short periods of
time intervals lasting 4, 8 and 16 seconds near the impulsive peak has been
examined. The results show little evidence for strong anisotropy and the mean
electron flux spectra are consistent with the isotropic electron distribution.
The 3-sigma level uncertainties, although energy and event dependent, are found
to suggest that anisotropic distribution with anisotropy larger than ~ 3 are
not consistent with the hard X-ray data. At energies above 150-200 keV, the
uncertainties are larger and thus the possible electron anisotropies could be
larger.
