  Aims: We present neutrino light curves and energy spectra for two
representative type Ia supernova explosion models: a pure deflagration and a
delayed detonation. Methods: We calculate the neutrino flux from $\beta$
processes using nuclear statistical equilibrium abundances convoluted with
approximate neutrino spectra of the individual nuclei and the thermal neutrino
spectrum (pair+plasma). Results: Although the two considered thermonuclear
supernova explosion scenarios are expected to produce almost identical
electromagnetic output, their neutrino signatures appear vastly different,
which allow an unambiguous identification of the explosion mechanism: a pure
deflagration produces a single peak in the neutrino light curve, while the
addition of the second maximum characterizes a delayed-detonation. We
identified the following main contributors to the neutrino signal: (1) weak
electron neutrino emission from electron captures (in particular on the protons
Co55 and Ni56) and numerous beta-active nuclei produced by the thermonuclear
flame and/or detonation front, (2) electron antineutrinos from positron
captures on neutrons, and (3) the thermal emission from pair annihilation. We
estimate that a pure deflagration supernova explosion at a distance of 1 kpc
would trigger about 14 events in the future 50 kt liquid scintillator detector
and some 19 events in a 0.5 Mt water Cherenkov-type detector. Conclusions:
While in contrast to core-collapse supernovae neutrinos carry only a very small
fraction of the energy produced in the thermonuclear supernova explosion, the
SN Ia neutrino signal provides information that allows us to unambiguously
distinguish between different possible explosion scenarios. These studies will
become feasible with the next generation of proposed neutrino observatories.

Solar and Stellar Astrophysics;High Energy Physics - Experiment;High Energy Physics - Phenomenology;Nuclear Experiment;Nuclear Theory