Evolution of the Global Temperature Structure of the Solar Corona Around the Last Solar Minimum

ALBERTO M. VASQUEZ; NUEVO, FEDERICO A.; HUANG, ZHENGUANG; FRAZIN, RICHARD A.

San Francisco, California

Congreso; American Geophysical Union, Fall Meeting; 2012

The combination of Differential Emission Measure Tomography (DEMT)with magnetic models allows determination of the electron density and electron temperature along individual magnetic field lines. The approach, named the Michigan Loop Diagnostic Technique (MLDT), has been recently first applied to study the last absolute minimum during Carrington rotation (CR) 2077, between solar cycles (SC)-23 and 24. In that work, two types of quiet Sun (QS) coronal loops were identified: "up" loops in which the temperature increases with height, and "down" loops in which the temperature decreases with height. While the first ones are expected, the latter ones were a surprise and, furthermore, found to be ubiquitous in the low-latitude corona. In the present work we refine and extend the analysis to several CRs around the last solar minimum. We show that the population of down loops, which is always located in the low-latitude region, was maximum at solar minimum. The number of down loops systematically increased during the declining phase of SC-23 and diminished during the rising phase of SC-24. We discuss the implications of this discovery for the investigation of the coronal heating problem.