E-Print Archive

There are 4491 abstracts currently viewable.


Advanced Search
Main Page Add New E-Print Submitter
News Help/FAQ About Preferences
Manage Key Phrase
On the Formation Height of the SDO/HMI Fe 6173 Doppler Signal  

Bernhard Fleck   Submitted: 2011-04-28 08:53

The Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) is designed to study oscillations and the mag- netic field in the solar photosphere. It observes the full solar disk in the Fe I absorption line at 6173AA . We use the output of a high-resolution 3D, time- dependent, radiation-hydrodynamic simulation based on the CO5BOLD code to calculate profiles F({lambda},x,y,t) for the Fe I 6173{AA} line. The emerging profiles F({lambda},x,y,t) are multiplied by a representative set of HMI filter transmission profiles R_i({lambda},1 leq i leq 6) and filtergrams I_i(x,y,t;1 leq i leq 6) are constructed for six wavelengths. Doppler velocities V_HMI(x,y,t) are determined from these filtergrams using a simplified version of the HMI pipeline. The Doppler velocities are correlated with the original velocities in the simulated atmosphere. The cross- correlation peaks near 100 km, suggesting that the HMI Doppler velocity signal is formed rather low in the solar atmosphere. The same analysis is performed for the SOHO/MDI Ni I line at 6768AA . The MDI Doppler signal is formed slightly higher at around 125 km. Taking into account the limited spatial resolution of the instruments, the apparent formation height of both the HMI and MDI Doppler signal increases by 40 to 50 km. We also study how uncertainties in the HMI filter-transmission profiles affect the calculated velocities.

Authors: B. Fleck, S. Couvidat, T. Straus
Projects: SDO-HMI

Publication Status: Solar Physics, in press
Last Modified: 2011-04-28 12:50
Go to main E-Print page  Edit Entry  Download Preprint  Delete Entry 

Go to main E-Print pageGo to main E-Print page.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
Delete AbstractDelete abstract.

Abstracts by Author
On the Formation Height of the SDO/HMI Fe 6173 Doppler Signal

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey

© 2000-2020 Solar Physics Group - Montana State University