Evidence for Temporal Variations in Polar Plumes
Abstract
In order to place empirical constraints on possible plasma heating processes and acceleration mechanisms for mass flows in polar plumes, we studied the variability of the O VI and MgX emissions from four plumes observed by the Harvard Skylab experiment. The observations consist of a 40 min sequence of spectroheliograms acquired with ∼2 min temporal resolution. We found that the MgX emission from each plume had a strong `dc' component and that any variations, if present, occurred at approximately the 10% (of the mean) level or less. This implies that temporal variations in the density and/or temperature were 5% or less. There were some statistically significant variations in the measured MgX signals. Two of the plumes decreased in brightness by approximately 10% during the 40 min period of the observations. In addition two plumes exhibited short-term (few minute) variations which appear to be statistically significant at a confidence level of >90%. The latter variations (if real) appear to be due to small (∼2 × 104 K) fluctuations in temperature caused by fluctuations in the local plasma heating rate.
- Publication:
-
Solar Physics
- Pub Date:
- November 1983
- DOI:
- 10.1007/BF00211954
- Bibcode:
- 1983SoPh...89...77W
- Keywords:
-
- Coronal Holes;
- Plasma Acceleration;
- Plasma Heating;
- Solar Spectra;
- Solar Wind;
- Extreme Ultraviolet Radiation;
- Periodic Variations;
- Radiant Flux Density;
- Solar Temperature;
- Statistical Analysis;
- Solar Physics;
- Heating Rate;
- Temporal Variation;
- Significant Variation;
- Confidence Level;
- Mass Flow