SPEARS Seminar: Exploring elusive red and blue shifts in solar coronal loops using multi-thread modelling

Doctor Robert Walsh, Jeremiah Horrocks Institute, University of Central Lancashire

Tuesday 15 May 2012, 1600-1700
Lecture Theatre, Charles Carter Building (A15)

Magnetic plasma loops have been termed the building blocks of the solar atmosphere. However, it has been postulated that the range of loop structures we can observe consist of many ''sub-resolution'' elements or strands. Thus a loop should be viewed is an amalgamation of these strands which could operate in thermal isolation from one another with a wide range of temperatures occurring across the structural elements.

This scenario could occur when the energy release mechanism consists of localised, discrete bursts of energy that are due to small scale reconnection sites within the coronal magnetic field- the nanoflare coronal heating mechanism. These energy bursts occur in a time-dependent manner, distributed along the loop/strand length, giving a heating function that depends on space and time.

An important observational discovery with the Hinode/EIS spectrometer is the existence of red and blue-shifts in coronal loops depending on the location within the active region and the temperature of the emission line in which the Doppler shifts are measured. This talk will show that red and blue-shifts can exist in different simulated Hinode/EIS passbands using a multi-thread model: cooler lines (Si VII) being dominated by red-shifts, whilst hotter lines (FeXV) are a combination of both. Characteristic Doppler shifts generated fit well with observed values. New high resolution images from NASA/SDO will also be used to examine possible flows.