E-Print Archive

There are 3047 abstracts currently viewable.
There is a problem with some abstracts that became corrupted following database issues. These will be restored as soon as possible.


Search:

Advanced Search
Options
Main Page Add New E-Print Submitter
Information
Feedback
News Help/FAQ About Preferences
Manage Key Phrase
Notification
Diagnosing Transient Ionization in Dynamic Events  

Gerry Doyle   Submitted: 2013-07-29 05:46

The present study aims to provide a diagnostic line ratio that will enable the observer to determine whether a plasma is in a state of transient ionization. We use the Atomic Data and Analysis Structure (ADAS) to calculate line contribution functions for two lines, Si IV 1394A and O IV 1401A, formed in the solar transition region. The generalized collisional-radiative theory is used. It includes all radiative and electron collisional processes, except for photon-induced processes. State-resolved direct ionization and recombination to and from the next ionization stage are also taken into account. For dynamic bursts with a decay time of a few seconds, the Si IV 1394A line can be enhanced by a factor of 2-4 in the first fraction of a second with the peak in the line contribution function occurring initially at a higher electron temperature due to transient ionization compared to ionization equilibrium conditions. On the other hand, the O IV 1401A does not show such an enhancement. Thus the ratio of these two lines, which can be observed with the Interface Region Imaging Spectrograph, can be used as a diagnostic of transient ionization. We show that simultaneous high-cadence observations of two lines formed in the solar transition region may be used as a direct diagnostic of whether the observed plasma is in transient ionization. The ratio of these two lines can change by a factor of four in a few seconds owing to transient ionization alone.

Authors: J.G. Doyle, A. Giunta, M.S. Madjarska, H. Summers, M. O'Mullane and A. Singh
Projects: Other

Publication Status: accepted
Last Modified: 2013-07-29 14:53
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

The Diagnostic Potential of Transition Region Lines under-going Transient Ionization in Dynamic Events  

Gerry Doyle   Submitted: 2012-04-30 05:00

We discuss the diagnostic potential of high cadence ultraviolet spectral data when transient ionization is considered. For this we use high cadence UV spectra taken during the impulsive phase of a solar flares (observed with instruments on-board the Solar Maximum Mission) which showed excellent correspondence with hard X-ray pulses. The ionization fraction of the transition region ion O V and in particular the contribution function for the O V 1371A line are computed within the Atomic Data and Analysis Structure, which is a collection of fundamental and derived atomic data and codes which manipulate them. Due to transient ionization, the O V 1371A line is enhanced in the first fraction of a second with the peak in the line contribution function occurring initially at a higher electron temperature than in ionization equilibrium. The rise time and enhancement factor depend mostly on the electron density. The fractional increase in the O V 1371A emissivity due to transient ionization can reach a factor of 2--4 and can explain the fast response in the line flux of transition regions ions during the impulsive phase of flares solely as a result of transient ionization. This technique can be used to diagnostic the electron temperature and density of solar flares observed with the forth-coming Interface Region Imaging Spectrograph.

Authors: J.G. Doyle, A. Giunta, A. Singh, M.S. Madjarska, H. Summers, B.J. Kellett & M. O'Mullane
Projects: Solar Max Misson

Publication Status: Solar Phys (accepted)
Last Modified: 2012-05-01 10:16
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Magnetic Reconnection resulting from Flux Emergence: Implications for Jet Formation in the lower solar atmosphere?  

Gerry Doyle   Submitted: 2011-09-29 01:47

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: J. Y. Ding, M. S. Madjarska, J. G. Doyle, Q. M. Lu, K. Vanninathan, and Z. Huang
Projects: None

Publication Status: accepted by A&A
Last Modified: 2011-09-29 14:10
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Magnetic topology of blinkers  

Gerry Doyle   Submitted: 2008-06-11 07:31

Here, we study brightening events in the transition region of the quiet Sun, also called `blinkers' using co-spatial and co-temporal spectroscopic, imaging and magnetogram data. The aim is to investigate the physical mechanism responsible for blinkers. We use an automated blinker identification procedure (BLIP) to identify blinker events in SoHO/CDS data. The 3D magnetic topology of the magnetic field in the blinker region is reconstructed based on SoHO/MDI magnetogram data. During 3 hrs of SoHO/CDS observations on 2006 January 18, 66 blinkers were identified in the O V 629A emission line. Out of them, a group comprising of 16 events were modelled here. They were found to be associated with the emergence of magnetic flux which gave rise to the appearance of, and multiple magnetic reconnection events across, an upper atmosphere (coronal) magnetic null point, along with a loop structure as observed with TRACE. This blinker group results from the release of energy that was accumulated during flux emergence, although whether all blinkers follow the same formation scenario requires further investigation using additional multi-instrument/multi-mission studies.

Authors: S. Subramanian, M.S. Madjarska, R.C. Maclean, J.G. Doyle, D. Bewsher
Projects: SoHO-CDS

Publication Status: accepted by A&A
Last Modified: 2008-09-23 21:00
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Subject will be restored when possible  

Gerry Doyle   Submitted: 2007-10-11 03:51

Using temporal series data from the Coronal Diagnostic Spectrometer (CDS) on SOHO, we seek to investigate plasma condensation through the use of spectroscopic analysis. In a space-time (X-T) type plot we show, for a number of transition region (TR) and coronal lines, the variation of radiance with time in an off-limb loop system. Noting a number of pixels where the radiance shows a sharp jump in value for the TR lines and a corresponding sharp decrease for the coronal lines, we investigate further and plot the radiance and velocity for these pixels as a function of time. Using standard Fourier techniques, together with a pre-whitening method, we measure all statistically significant frequencies present in the time series so created. We find that, for the cooler lines of He I 584A and O V 629A there are sharp increases in radiance, accompanied by large blueshifted velocities. In the case of O V there is then a substantial rebound to redshifted velocities when the strong brightening fades. The sharp increase in radiance and blueshifted velocity in the cooler lines is accompanied by a corresponding decrease in the radiance of the coronal lines (Mg X 624A, Fe XVI 360A, Si XII 520A), but with no corresponding change in their velocity values implying an evacuation of plasma. From the Fourier analysis, evidence is found for a possible 1st and 2nd harmonic in the He I and O V lines, indicative of standing waves in loops. We conclude that what we are seeing is the first spectroscopic evidence of plasma condensation taking place in coronal loops.

Authors: E. O'Shea, D. Banerjee and J.G. Doyle
Projects: SoHO-CDS

Publication Status: A&A L (in press)
Last Modified: 2007-10-11 09:40
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Subject will be restored when possible  

Gerry Doyle   Submitted: 2007-10-11 03:50

Aims. Using temporal series data from the Coronal Diagnostic Spectrometer (CDS) on SOHO, we seek to investigate plasma condensation through the use of spectroscopic analysis. Methods. Using a space-time (X-T) type plot we show, for a number of transition region (TR) and coronal lines, the variation of radiance with time in an off-limb loop system. Noting a number of pixels where the radiance shows a sharp jump in value for the TR lines and a corresponding sharp decrease for the coronal lines, we investigate further and plot the radiance and velocity for these pixels as a function of time. Using standard Fourier techniques, together with a pre-whitening method, we measure all statistically significant frequencies present in the time series so created. Results. We find that, for the cooler lines of He I 584A and O V 629A there are sharp increases in radiance, accompanied by large blueshifted velocities. In the case of O V there is then a substantial rebound to redshifted velocities when the strong brightening fades. The sharp increase in radiance and blueshifted velocity in the cooler lines is accompanied by a corresponding decrease in the radiance of the coronal lines (Mg X 624A, Fe XVI 360A, Si XII 520A), but with no corresponding change in their velocity values implying an evacuation of plasma. From the Fourier analysis, evidence is found for a possible 1st and 2nd harmonic in the He I and O V lines, indicative of standing waves in loops. Conclusions. We conclude that what we are seeing is the first spectroscopic evidence of plasma condensation taking place in coronal loops.

Authors: E. O'Shea, D. Banerjee and J.G. Doyle
Projects: SoHO-CDS

Publication Status: A&A L (in press)
Last Modified: 2007-10-11 03:50
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Subject will be restored when possible  

Gerry Doyle   Submitted: 2007-10-11 02:44

We report on active region EUV dynamic events observed simultaneously at high-cadence with SUMER/SoHO and TRACE. Although the features appear in the TRACE Fe ix/x 171A images as jets seen in projection on the solar disk, the SUMER spectral line profiles suggest that the plasma has been driven along a curved large scale magnetic structure, a pre-existing loop. The SUMER observations were carried out in spectral lines covering a large temperature range from 10^4 K to 10^6 K. The spectral analysis revealed that a sudden heating from an energy deposition is followed by a high velocity plasma flow. The Doppler velocities were found to be in the range from 90 to 160 km/s. The heating process has a duration which is below the SUMER exposure time of 25 s while the lifetime of the events is from 5 to 15 min. The additional check on soft X-ray Yohkoh images shows that the features most probably reach 3 MK (X-ray) temperatures. The spectroscopic analysis showed no existence of cold material during the events.

Authors: M.S. Madjarska, J.G. Doyle, D. Innes and W. Curdt
Projects: SoHO-SUMER

Publication Status: ApJ L (in press)
Last Modified: 2007-10-11 09:41
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Subject will be restored when possible  

Gerry Doyle   Submitted: 2007-10-11 02:43

We report on active region EUV dynamic events observed simultaneously at high-cadence with SUMER/SoHO and TRACE. Although the features appear in the TRACE Fe ix/x 171A images as jets seen in projection on the solar disk, the SUMER spectral line profiles suggest that the plasma has been driven along a curved large scale magnetic structure, a pre-existing loop. The SUMER observations were carried out in spectral lines covering a large temperature range from 10^4 K to 10^6 K. The spectral analysis revealed that a sudden heating from an energy deposition is followed by a high velocity plasma flow. The Doppler velocities were found to be in the range from 90 to 160 km/s. The heating process has a duration which is below the SUMER exposure time of 25 s while the lifetime of the events is from 5 to 15 min. The additional check on soft X-ray Yohkoh images shows that the features most probably reach 3 MK (X-ray) temperatures. The spectroscopic analysis showed no existence of cold material during the events.

Authors: M.S. Madjarska, J.G. Doyle, D. Innes and W. Curdt
Projects: SoHO-SUMER

Publication Status: ApJ L (in press)
Last Modified: 2007-10-11 02:43
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
Diagnosing Transient Ionization in Dynamic Events
The Diagnostic Potential of Transition Region Lines under-going Transient Ionization in Dynamic Events
Magnetic Reconnection resulting from Flux Emergence: Implications for Jet Formation in the lower solar atmosphere?
Magnetic topology of blinkers
Subject will be restored when possible
Subject will be restored when possible
Subject will be restored when possible
Subject will be restored when possible

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