E-Print Archive

There are 3783 abstracts currently viewable.


Search:

Advanced Search
Options
Main Page Add New E-Print Submitter
Information
Feedback
News Help/FAQ About Preferences
Manage Key Phrase
Notification
CORONAL MAGNETIC FIELD MEASUREMENT FROM EUV IMAGES MADE BY THE SOLAR DYNAMICS OBSERVATORY  

Nat Gopalswamy Gopalswamy   Submitted: 2013-01-05 05:19

By measuring the geometrical properties of the coronal mass ejection (CME) flux rope and the leading shock observed on 2010 June 13 by the Solar Dynamics Observatory (SDO) mission's Atmospheric Imaging Assembly (AIA) we determine the Alfvén speed and the magnetic field strength in the inner corona at a heliocentric distance of ~ 1.4 Rs. The basic measurements are the shock standoff distance (ΔR) ahead of the CME flux rope, the radius of curvature of the flux rope (Rc), and the shock speed. We first derive the Alfvénic Mach number (M) using the relationship, ΔR/Rc = 0.81[(γ-1)M2 + 2]/[(γ+1)(M2-1)], where γ is the only parameter that needed to be assumed. For γ =4/3, the Mach number declined from 3.7 to 1.5 indicating shock weakening within the field of view of the imager. The shock formation coincided with the appearance of a type II radio burst at a frequency of ~300 MHz (harmonic component), providing an independent confirmation of the shock. The shock compression ratio derived from the radio dynamic spectrum was found to be consistent with that derived from the theory of fast mode MHD shocks. From the measured shock speed and the derived Mach number, we found the Alfvén speed to increase from ~140 km s-1 to 460 km s-1 over the distance range 1.2 to 1.5 Rs. By deriving the upstream plasma density from the emission frequency of the associated type II radio burst, we determined the coronal magnetic field to be in the range 1.3 to 1.5 G. The derived magnetic field values are consistent with other estimates in a similar distance range. This work demonstrates that the EUV imagers, in the presence of radio dynamic spectra, can be used as coronal magnetometers.

Authors: Nat Gopalswamy, Nariaki Nitta, Sachiko Akiyama, Pertti Makela, and Seiji Yashiro
Projects: SDO-AIA,SoHO-LASCO

Publication Status: The Astrophysical Journal, 744, 72, 2012
Last Modified: 2013-01-07 12:46
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 


Key
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
CORONAL MAGNETIC FIELD MEASUREMENT FROM EUV IMAGES MADE BY THE SOLAR DYNAMICS OBSERVATORY

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



© 2003 Solar Physics Group - Montana State University