We have carried out Very Large Array ( VLA ) continuum observations to study the variability of Sgr A* at 43 GHz ( \lambda =7mm ) and 22 GHz ( \lambda =13mm ) .
A low level of flare activity has been detected with a duration of \sim 2 hours at these frequencies , showing the peak flare emission at 43 GHz leading the 22 GHz peak flare by \sim 20 to 40 minutes .
The overall characteristics of the flare emission are interpreted in terms of the plasmon model of Van der Laan ( 1966 ) by considering the ejection and adiabatically expansion of a uniform , spherical plasma blob due to flare activity .
The observed peak of the flare emission with a spectral index \nu ^ { - \alpha } of \alpha =1.6 is consistent with the prediction that the peak emission shifts toward lower frequencies in an adiabatically-expanding self-absorbed source .
We present the expected synchrotron light curves for an expanding blob as well as the peak frequency emission as a function of the energy spectral index constrained by the available flaring measurements in near-IR , sub-millimeter , millimeter and radio wavelengths .
We note that the blob model is consistent with the available measurements , however , we can not rule out the jet of Sgr A* .
If expanding material leaves the gravitational potential of Sgr A* , the total mass-loss rate of nonthermal and thermal particles is estimated to be \leq 2 \times 10 ^ { -8 } M _ { \odot } yr ^ { -1 } .
We discuss the implication of the mass-loss rate since this value matches closely with the estimated accretion rate based on polarization measurements .