  We calculate the thermal flux of low-energy solar neutrinos and antineutrinos
of all flavors arising from a variety of neutrino pair processes: Compton
production (including plasmon-pole diagrams), neutral current decay of
thermally populated nuclear states, plasmon decay, and electron transitions
from free to atomic bound states. The resulting flux density per flavor is
significant (10E8-10E9/cm2/sec/MeV) below about 5 keV, and the distributions
fill much of the valley between the high-energy edge of the cosmic background
neutrino spectrum and the low energy tails of the pp-chain electron neutrino
and terrestrial electron antineutrino spectra. Thermal neutrinos carry
information on the solar core temperature distribution and on heavy flavor
masses in the range of 1 keV. The detection of these neutrinos is a daunting
but interesting challenge.
