Microvariability and Long-Term Variability of Four Blazars

Long-term light curves of four blazars, Mrk 421, Mrk 501, 3C 345, and BL Lacertae were constructed using archival data and supplemented with new observations. The occurrences of microvariability are correlated temporally with long-term optical activity in the light curves. Although the statistics are not conclusive, we find evidence that microvariability is correlated with rapid flux changes rather than specific flux levels. We discuss the implications of these results for quasar variability models.