How does the chromosphere regulate mass and energy supply to the corona and the solar wind?

Ubiquitous rapid upflows with velocities of order 50-150 km/s in the lower solar atmosphere have recently been revealed (De Pontieu et al. 2009a, McIntosh & De Pontieu, 2009a,b). Signatures of these events have been observed with a broad range of imaging and spectroscopic instruments in the chromosphere (in the form of spicules, De Pontieu et al. 2009a, Rouppe van der Voort et al. 2009) and in the transition region and corona (in the form of blueward asymmetries of transition region and coronal spectral line profiles, and propagating disturbances in coronal imaging). Preliminary analysis suggests that these upflows are part of a previously undetected, but relentless transfer of mass between the dense lower atmosphere and tenuous corona in which a potentially significant amount of plasma may be heated to coronal temperatures at very low heights, in the upper chromosphere, transition region and low corona.

There are many unresolved issues regarding the properties, formation mechanism and impact of these rapid upflow events. How ubiquitous are they? Can we determine their significance for the coronal energy and mass balance, e.g., by determining their occurrence rate (spatio-temporal filling factor), plasma density and energy flux? What drives these upflows?
These unresolved issues may be addressed by using a powerful combination of new spectral and imaging data with high cadence and high spatial and spectral resolution from Hinode, SDO, SST/CRISP and IRIS and comparing the observations in detail with our 3D radiation magnetohydrodynamic simulations. We will:
  1. perform a detailed analysis of the magnetic field configuration, and momentum/energy balance at the roots of jets found in the simulations;
  2. calculate synthetic diagnostics of chromospheric (including optically thick lines such as Mg II k or H-alpha, using the MULTI3D code), transition region and coronal lines and compare the synthetic line profiles of simulated rapid upflow events with our observations: e.g., the dependence of velocity on temperature and magnetic field configurations;
  3. perform numerical simulations with higher spatial resolution: preliminary analysis of such runs show more violent dynamics, likely because energy release occurs on smaller spatial scales;
  4. perform statistical analysis of the properties of a large number of jet-like features to determine the various formation mechanisms, and the impact of such events on the coronal mass and energy balance.
Published Feb. 3, 2011 4:06 PM