Temporal variability in the electron density at the solar transition region

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 Te ∼ 1.5 105 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.