Context. The international Whole Earth Blazar Telescope (WEBT) consortium planned and carried out three days of intensive micro-variability observations of S5 0716+714 from February 22, 2009 to February 25, 2009. This object was chosen due to its bright apparent magnitude range, its high declination, and its very large duty cycle for micro-variations. Aims. We report here on the long continuous optical micro-variability light curve of 0716+714 obtained during the multi-site observing campaign during which the Blazar showed almost constant variability over a 0.5 mag range. The resulting light curve is presented here for the first time.Observations from participating observatories were corrected for instrumental differences and combined to construct the overall smoothed light curve. Methods. Thirty-six observatories in sixteen countries participated in this continuous monitoring program and twenty of them submitted data for compilation into a continuous light curve. The light curve was analyzed using several techniques including Fourier transform, Wavelet and noise analysis techniques. Those results led us to model the light curve by attributing the variations to a series of synchrotron pulses. Results. We have interpreted the observed microvariations in this extended light curve in terms of a new model consisting of individual stochastic pulses due to cells in a turbulent jet which are energized by a passing shock and cool by means of synchrotron emission. We obtained an excellent fit to the 72-hour light curve with the synchrotron pulse model.

We present the results of a long-term study designed to investigate the nature of micro-variability in blazars carried out primarily at the Southeastern Association for Research in Astronomy (SARA) observatories. We analyzed micro-variability data of fifteen OVV quasars and BL Lac sources collected from 1995 to 2021. The data set consists of single-band light curves interspersed with multi-color and micro-variability observations. This paper reports over 900 nights of CCD observations. We also incorporated observations from other observers as well as observations gleaned from the literature into our analysis. We employed differential photometry to measure magnitudes and then construct the long-term and micro-variability light curves. Our results indicate that there is no correlation between the presence of micro-variations and the brightness of the source. We present a viable theory to explain the intermittent micro-variability as pulses of radiation emitted by individual turbulent cells in the relativistic jet, which are stimulated by a passing shock wave. We present model fits and test results for various data sets, including WEBT light curves, Kepler light curves and a TESS light curve. Although the consensus in the community is that blazar jets must be turbulent, the identification of micro-variations as manifestations of actual turbulent cells is important for modeling these turbulent jets. We can obtain estimates of cell sizes (assuming a shock speed), and the distribution of cell sizes derived from observations is consistent with numerical simulation predictions.

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