A new model for solar spike bursts is considered based on the interaction o
f Langmuir waves with ion-sound waves: l + s --> t. Such a mechanism can op
erate in shock fronts, propagating from a magnetic reconnection region. New
observations of microwave millisecond spikes are discussed. They have been
observed in two events: 4 November 1997 between 05:52-06:10 UT and 28 Nove
mber 1997 between 05:00-05:10 UT using the multichannel spectrograph in the
range 2.6-3.8 GHz of Beijing AO. Yohkoh/SXT images in the AR and SOHO EIT
images testify to a reconstruction of bright loops after the escape of a CM
E. A fast shock front might be manifested as a very bright line in T-e SXT
maps (up to 20 MK) above dense structures in emission measure (EM) maps. Mo
reover one can see at the moment of spike emission (for the 28 November 199
7 event) an additional maximum at the loop top on the HXR map in the AR as
principal evidence of fast shock propagation. The model gives the ordinary
mode of spike emission. Sometimes we observed a different polarization of m
icrowave spikes that might be connected with the depolarization of the emis
sion in the transverse magnetic field and rather in the vanishing magnetic
field in the middle of the QT region. Duration and frequency band of isolat
ed spikes are connected with parameters of fast particle beams and shock fr
ont. Millisecond microwave spikes are probably a unique manifestation of fl
are fast shocks in the radio emission.