Tom Donaly wrote:
Whether it's dust, snow, or the atmospheric electric field charging the
antenna, the noise is still corona discharge. At least that's what most
of the sources say.

It is my understanding that the air around a conductor must
ionize for it to be defined as corona. Obviously, there is
a time when charge is transferred to the antenna before
ionization (corona) occurs. Corona is defined as a discharge
function. The charging function must necessarily occur before
corona. If the charge is not allowed to accumulate up to the
ionization level, corona will not occur, by definition.
Precipitation static occurs before the corona threshold is
reached. For what it's worth, here's what the 2000 ARRL
Handbook says:

"Precipitation Static and Corona Discharge"

"Precipitation static is an almost continuous hash-type noise
that often accompanies various kinds of precipitation, including
snowfall. Precipitation static is caused by rain drops, snowflakes
or even *wind-blown dust*, transferring a small electrical charge
on contact with an antenna."

"Electrical fields under thunderstorms are sufficient to place
many objects such as trees, hair and antennas, into corona
discharge."

Although not stated explicitly, seems to me there is a strong
implication that precipitation static is not strong enough to
ionize the air, i.e. not strong enough to cause corona to exist.
Indeed, the arcing at a coax connector or the DC grounding of
an antenna may be enough to prevent ionization and corona
during a precipitation static episode.
--
73, Cecil http://www.qsl.net/w5dxp