We calculate the absolute intensity and anisotropies of the Lyman- \alpha radiation field present during the epoch of reionization .
We consider emission from both galaxies and the intergalactic medium ( IGM ) and take into account the main contributions to the production of Lyman- \alpha photons : recombinations , collisions , continuum emission from galaxies and scattering of Lyman-n photons in the IGM .
We find that the emission from individual galaxies dominates over the IGM with a total Lyman- \alpha intensity ( times frequency ) of about ( 1.43 - 3.57 ) \times 10 ^ { -8 } { erg s ^ { -1 } cm ^ { -2 } sr ^ { -1 } } at a redshift of 7 .
This intensity level is low so it is unlikely that the Lyman- \alpha background during reionization can be established by an experiment aiming at an absolute background light measurement .
Instead we consider Lyman- \alpha intensity mapping with the aim of measuring the anisotropy power spectrum which has rms fluctuations at the level of 1 \times 10 ^ { -16 } { [ erg s ^ { -1 } cm ^ { -2 } sr ^ { -1 } ] ^ { 2 } } at a few Mpc scales .
These anisotropies could be measured with a spectrometer at near-IR wavelengths from 0.9 to 1.4 \mu m with fields in the order of 0.5 to 1 sq .
degrees .
We recommend that existing ground-based programs using narrow band filters also pursue intensity fluctuations to study statistics on the spatial distribution of faint Lyman- \alpha emitters .
We also discuss the cross-correlation signal with 21 cm experiments that probe HI in the IGM during reionization .
A dedicated sub-orbital or space-based Lyman- \alpha intensity mapping experiment could provide a viable complimentary approach to probe reionization , when compared to 21 cm experiments , and is likely within experimental reach .