Ion traps at the Sun: observational evidence
Abstract
Our understanding of thermal processes in the solar atmosphere relies in particular on diagnostics of the plasma emission in ultraviolet and extreme ultraviolet (EUV). These emissions are produced by heavy ions in various ionization states and depend on the amount of these ions and on the plasma temperature and density. Any non-uniformity of the distribution of elements can therefore affect our thermal diagnostics of the solar atmosphere. Using a simple model of ion propagation in current carrying magnetic loops, we theoretically predicted a concentration (depletion) of ions in regions of the solar atmosphere associated with upward-directed (downward-directed) current densities. We present here the data analysis that leads to observational evidence supporting this prediction. We analyze the distribution of EUV emission from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamic Observatory (SDO) in regard to positive and negative vertical current densities calculated at the photospheric level using the spectropolarimetric data from the Helioseismic Magnetic Imager (SDO/HMI). A statistical analysis of these distributions was performed for several active regions and at several times, for several EUV wavelengths. We found a significant excess in EUV brightness in the areas with positive (i.e. upward) current densities rather than negative. We call such areas of heavy ion concentrations the "ion traps". We will discuss the implication of our result for the first ionization potential (FIP) effect in particular, as well as the next theoretical and observational developments foreseen to deepen our understanding of this effect in the dynamic coronal environment during and between solar flares.
- Publication:
-
2018 Triennial Earth-Sun Summit (TESS)
- Pub Date:
- May 2018
- Bibcode:
- 2018tess.conf20955M