What has happened to the Neutrinos?
The current explanation for the 'Solar Neutrino Problem' is:
HELIO (Solar) Seismology
Sound bounces around the inside of the Sun, just like is
seen in earthquakes on the Earth.
The bouncing 'rays' of sound create a ringing, which is seen as
waves on the surface of the Sun.
Scientists study time-lapse photography of the Sun to measure these
waves.
Measuring the surface waves seen can be used with models to obtain measurements of the density, pressure, composition and temperature of the Sun's interior--Provided we can simultaneously solve for 10 million different ringing patterns at once!