  3He-rich solar energetic particles (SEPs) are believed to be accelerated in
solar flares or jets by a mechanism that depends on the ion charge-to-mass
(Q/M) ratio. It implies that the flare plasma characteristics (e.g.,
temperature) may be effective in determining the elemental abundances of
3He-rich SEPs. This study examines the relation between the suprathermal (<0.2
MeV/nuc) abundances of the He-Fe ions measured on the Advanced Composition
Explorer and temperature in the solar sources for 24 3He-rich SEP events in the
period 2010-2015. The differential emission measure technique is applied to
derive the temperature of the source regions from the extreme ultraviolet
imaging observations on the Solar Dynamics Observatory. The obtained
temperature distribution peaks at 2.0-2.5 MK that is surprisingly consistent
with earlier findings based on in-situ elemental abundance or charge state
measurements. We have found a significant anti-correlation between 3He/4He
ratio and solar source temperature with a coefficient -0.6. It is most likely
caused by non-charge-stripping processes, as both isotopes would be fully
ionized in the inferred temperature range. This study shows that the elemental
ratios 4He/O, N/O, Ne/O, Si/O, S/O, Ca/O, Fe/O generally behave with
temperature as expected from abundance enhancement calculations at ionization
equilibrium. The C and Mg, the two species with small changes in the Q/M ratio
in the obtained temperature range, show no such behavior with temperature and
could be influenced by similar processes as for the 3He/4He ratio.
