Temporal variability in the electron density at the solar transition region

Abstract

The electron density as measured in the transition region of a coronal hole, a `quiet' Sun region at disk center plus an active region shows variations of up to a factor of two at T_e ~ 1.5 10<sup>5</sup> K, lasting at most only a few minutes. There is remarkable agreement between the number of such variations, their temporal variability and duration in the coronal hole and `quiet' Sun datasets, consistent with an earlier bright point study. There appears to be evidence of super-granular cells, with the increases in electron density occurring along the network boundaries. At some locations, periodicities of between 8 and 16 min are visible in the electron density variations. We associate these variations with the sites of explosive events.