E-Print Archive

There are 3977 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
Simulating coronal loop implosion and compressible wave modes in a flare hit active region  

Aveek Sarkar   Submitted: 2017-11-22 03:20

There is considerable observational evidence of implosion of magnetic loop systems inside solar coronal active regions following high energy events like solar flares. In this work, we propose that such collapse can be modeled in three dimensions quite accurately within the framework of ideal magnetohydrodynamics. We furthermore argue that the dynamics of loop implosion is only sensitive to the transmitted disturbance of one or more of the system variables, e.g. velocity generated at the event site. This indicates that to understand loop implosion, it is sensible to leave the event site out of the simulated active region. Towards our goal, a velocity pulse is introduced to model the transmitted disturbance generated at the event site. Magnetic field lines inside our simulated active region are traced in real time, and it is demonstrated that the subsequent dynamics of the simulated loops closely resemble observed imploding loops. Our work highlights the role of plasma β in regards to the rigidity of the loop systems and how that might affect the imploding loops' dynamics. Compressible magnetohydrodynamic modes such as kink and sausage are also shown to be generated during such processes, in accordance with observations.

Authors: Aveek Sarkar, Bhargav Vaidya, Soumitra Hazra, Jishnu Bhattacharyya
Projects: None

Publication Status: accepted in ApJ
Last Modified: 2017-11-22 13:21
Go to main E-Print page  Edit Entry  Download Preprint  Delete Entry 

Modeling solar coronal bright point oscillations with multiple nanoflare heated loops  

Aveek Sarkar   Submitted: 2015-07-22 23:43

Intensity oscillations of coronal bright points (BPs) have been studied for past several years. It has been known for a while that these BPs are closed magnetic loop like structures. However, initiation of such intensity oscillations is still an enigma. There have been many suggestions to explain these oscillations, but modeling of such BPs have not been explored so far. Using a multithreaded nanoflare heated loop model we study the behavior of such BPs in this work. We compute typical loop lengths of BPs using potential field line extrapolation of available data (Chandrashekhar et al. 2013), and set this as the length of our simulated loops. We produce intensity like observables through forward modeling and analyze the intensity time series using wavelet analysis, as was done by previous observers. The result reveals similar intensity oscillation periods reported in past observations. It is suggested these oscillations are actually shock wave propagations along the loop. We also show that if one considers different background subtractions, one can extract adiabatic standing modes from the intensity time series data as well, both from the observed and simulated data.

Authors: K Chandrashekhar, Aveek Sarkar
Projects: None

Publication Status: ApJ Accepted
Last Modified: 2015-07-23 10:11
Go to main E-Print page  Edit Entry  Download Preprint  Delete Entry 

EUV Observational consequences of the spatial localisation of nanoflare heating within a multi-stranded atmospheric loop  

Aveek Sarkar   Submitted: 2009-05-06 19:08

Determining the preferred spatial location of the energy input to solar coronal loops would be an important step forward towards a more complete understanding of the coronal heating problem. Following on from Sarkar & Walsh (2008) this paper presents a short 10e9 cm ``global loop'' as 125 individual strands, where each strand is modelled independently by a one-dimensional hydrodynamic simulation. The strands undergo small-scale episodic heating and are coupled together through the frequency distribution of the total energy input to the loop which follows a power law distribution with index ~ 2.29. The spatial preference of the swarm of heating events from apex to footpoint is investigated. From a theoretical perspective, the resulting emission measure weighted temperature profiles along these two extreme cases does demonstrate a possible observable difference. Subsequently, the simulated output is folded through the TRACE instrument response functions and a re-derivation of the temperature using different filter-ratio techniques is performed. Given the multi-thermal scenario created by this many strand loop model, a broad differential emission measure results; the subsequent double and triple filter ratios are very similar to those obtained from observations. However, any potential observational signature to differentiate between apex and footpoint dominant heating is possibly below instrumental thresholds. The consequences of using a broadband instrument like TRACE and Hinode-XRT in this way are discussed.

Authors: Aveek Sarkar, Robert W Walsh
Projects: None

Publication Status: Astrophysical Journal (Accepted)
Last Modified: 2009-05-07 06:25
Go to main E-Print page  Edit Entry  Download Preprint  Delete Entry 

Subject will be restored when possible  

Aveek Sarkar   Submitted: 2007-10-11 02:47

There is a growing body of evidence that the plasma loops seen with current instrumentation (SOHO, TRACE and Hinode) may consist of many sub-resolution elements or strands. Thus, the overall plasma evolution we observe in these features could be the cumulative result of numerous individual strands undergoing sporadic heating. This paper presents a short (109 cm equiv 10 Mm) ``global loop'' as 125 individual strands where each strand is modelled independently by a one-dimensional hydrodynamic simulation. The energy release mechanism across the strands consists of localised, discrete heating events (nano-flares). The strands are ``coupled'' together through the frequency distribution of the total energy input to the loop which follows a power law distribution with index α . The location and lifetime of each energy event occuring is random. Although a typical strand can go through a series of well-defined heating/cooling cycles, when the strands are combined, the overall quasi-static thermal profile for the global loop reproduces a hot apex/cool base structure. As α increases (from 0 to 2.29 to 3.29), more weight is given to the smallest heating episodes. Subsequently, the overall global loop apex temperature increases while the variation of the temperature around that value decreases. Any further increase in α saturates the loop apex temperature variations at the current simulation resolution. The effect of increasing the number of strands and the loop length as well as the implications of these results upon possible future observing campaigns for TRACE and Hinode are discussed.

Authors: Aveek Sarkar, Robert W Walsh
Projects: None

Publication Status: submitted
Last Modified: 2007-10-11 09:40
Go to main E-Print page  Edit Entry  Download Preprint  Delete Entry 

Subject will be restored when possible  

Aveek Sarkar   Submitted: 2007-10-11 02:47

There is a growing body of evidence that the plasma loops seen with current instrumentation (SOHO, TRACE and Hinode) may consist of many sub-resolution elements or strands. Thus, the overall plasma evolution we observe in these features could be the cumulative result of numerous individual strands undergoing sporadic heating. This paper presents a short (109 cm equiv 10 Mm) ``global loop'' as 125 individual strands where each strand is modelled independently by a one-dimensional hydrodynamic simulation. The energy release mechanism across the strands consists of localised, discrete heating events (nano-flares). The strands are ``coupled'' together through the frequency distribution of the total energy input to the loop which follows a power law distribution with index α . The location and lifetime of each energy event occuring is random. Although a typical strand can go through a series of well-defined heating/cooling cycles, when the strands are combined, the overall quasi-static thermal profile for the global loop reproduces a hot apex/cool base structure. As α increases (from 0 to 2.29 to 3.29), more weight is given to the smallest heating episodes. Subsequently, the overall global loop apex temperature increases while the variation of the temperature around that value decreases. Any further increase in α saturates the loop apex temperature variations at the current simulation resolution. The effect of increasing the number of strands and the loop length as well as the implications of these results upon possible future observing campaigns for TRACE and Hinode are discussed.

Authors: Aveek Sarkar, Robert W Walsh
Projects:

Publication Status: ApJ(submitted)
Last Modified: 2007-10-15 17:11
Go to main E-Print page  Edit Entry  Download Preprint  Delete Entry 

Subject will be restored when possible  

Aveek Sarkar   Submitted: 2007-10-11 02:47

There is a growing body of evidence that the plasma loops seen with current instrumentation (SOHO, TRACE and Hinode) may consist of many subresolution elements or strands. Thus, the overall plasma evolution we observe in these features could be the cumulative result of numerous individual strands undergoing sporadic heating. This paper presents a short (109 cm ≡ 10 Mm) "global loop" as 125 individual strands where each strand is modelled independently by a one-dimensional hydrodynamic simulation. The energy release mechanism across the strands consists of localised, discrete heating events (nano-flares). The strands are "coupled" together through the frequency distribution of the total energy input to the loop which follows a power law distribution with index α. The location and lifetime of each energy event occurring is random. Although a typical strand can go through a series of well-defined heating/cooling cycles, when the strands are combined, the overall quasi-static emission measure weighted thermal profile for the global loop reproduces a hot apex/cool base structure. Localised cool plasma blobs are seen to travel along individual strands which could cause the loop to "disappear" from coronal emission and appear in transition or chromospheric ones. As α increases (from 0 to 2.29 to 3.29), more weight is given to the smallest heating episodes. Consequently, the overall global loop apex temperature increases while the variation of the temperature around that value decreases. Any further increase in α saturates the loop apex temperature variations at the current simulation resolution. The effect of increasing the number of strands and the loop length as well as the implications of these results upon possible future observing campaigns for TRACE and Hinode are discussed.

Authors: Aveek Sarkar, Robert W Walsh
Projects: None

Publication Status: ApJ(accepted)
Last Modified: 2008-04-22 16:25
Go to main E-Print page  Edit Entry  Download Preprint  Delete Entry 

Subject will be restored when possible  

Aveek Sarkar   Submitted: 2007-10-11 02:47

There is a growing body of evidence that the plasma loops seen with current instrumentation (SOHO, TRACE and Hinode) may consist of many subresolution elements or strands. Thus, the overall plasma evolution we observe in these features could be the cumulative result of numerous individual strands undergoing sporadic heating. This paper presents a short (109 cm ≡ 10 Mm) `global loop' as 125 individual strands where each strand is modelled independently by a one-dimensional hydrodynamic simulation. The energy release mechanism across the strands consists of localised, discrete heating events (nano-flares). The strands are "coupled" together through the frequency distribution of the total energy input to the loop which follows a power law distribution with index α. The location and lifetime of each energy event occurring is random. Although a typical strand can go through a series of well-defined heating/cooling cycles, when the strands are combined, the overall quasi-static emission measure weighted thermal profile for the global loop reproduces a hot apex/cool base structure. Localised cool plasma blobs are seen to travel along individual strands which could cause the loop to "disappear" from coronal emission and appear in transition or chromospheric ones. As α increases (from 0 to 2.29 to 3.29), more weight is given to the smallest heating episodes. Consequently, the overall global loop apex temperature increases while the variation of the temperature around that value decreases. Any further increase in α saturates the loop apex temperature variations at the current simulation resolution. The effect of increasing the number of strands and the loop length as well as the implications of these results upon possible future observing campaigns for TRACE and Hinode are discussed.

Authors: Aveek Sarkar, Robert W Walsh
Projects:

Publication Status: ApJ(accepted)
Last Modified: 2008-04-22 16:26
Go to main E-Print page  Edit Entry  Download Preprint  Delete Entry 

Subject will be restored when possible  

Aveek Sarkar   Submitted: 2007-10-11 02:47

There is a growing body of evidence that the plasma loops seen with current instrumentation (SOHO, TRACE and Hinode) may consist of many subresolution elements or strands. Thus, the overall plasma evolution we observe in these features could be the cumulative result of numerous individual strands undergoing sporadic heating. This paper presents a short (109 cm ≡ 10 Mm) `global loop' as 125 individual strands where each strand is modelled independently by a one-dimensional hydrodynamic simulation. The energy release mechanism across the strands consists of localised, discrete heating events (nano-flares). The strands are `coupled' together through the frequency distribution of the total energy input to the loop which follows a power law distribution with index α. The location and lifetime of each energy event occurring is random. Although a typical strand can go through a series of well-defined heating/cooling cycles, when the strands are combined, the overall quasi-static emission measure weighted thermal profile for the global loop reproduces a hot apex/cool base structure. Localised cool plasma blobs are seen to travel along individual strands which could cause the loop to "disappear" from coronal emission and appear in transition or chromospheric ones. As α increases (from 0 to 2.29 to 3.29), more weight is given to the smallest heating episodes. Consequently, the overall global loop apex temperature increases while the variation of the temperature around that value decreases. Any further increase in α saturates the loop apex temperature variations at the current simulation resolution. The effect of increasing the number of strands and the loop length as well as the implications of these results upon possible future observing campaigns for TRACE and Hinode are discussed.

Authors: Aveek Sarkar, Robert W Walsh
Projects: None

Publication Status: ApJ(accepted)
Last Modified: 2008-04-22 16:28
Go to main E-Print page  Edit Entry  Download Preprint  Delete Entry 

Subject will be restored when possible  

Aveek Sarkar   Submitted: 2007-10-11 02:47

There is a growing body of evidence that the plasma loops seen with current instrumentation (SOHO, TRACE and Hinode) may consist of many subresolution elements or strands. Thus, the overall plasma evolution we observe in these features could be the cumulative result of numerous individual strands undergoing sporadic heating. This paper presents a short (109 cm ≡ 10 Mm) `global loop' as 125 individual strands where each strand is modelled independently by a one-dimensional hydrodynamic simulation. The energy release mechanism across the strands consists of localised, discrete heating events (nano-flares). The strands are ''coupled'' together through the frequency distribution of the total energy input to the loop which follows a power law distribution with index α. The location and lifetime of each energy event occurring is random. Although a typical strand can go through a series of well-defined heating/cooling cycles, when the strands are combined, the overall quasi-static emission measure weighted thermal profile for the global loop reproduces a hot apex/cool base structure. Localised cool plasma blobs are seen to travel along individual strands which could cause the loop to `disappear' from coronal emission and appear in transition or chromospheric ones. As α increases (from 0 to 2.29 to 3.29), more weight is given to the smallest heating episodes. Consequently, the overall global loop apex temperature increases while the variation of the temperature around that value decreases. Any further increase in α saturates the loop apex temperature variations at the current simulation resolution. The effect of increasing the number of strands and the loop length as well as the implications of these results upon possible future observing campaigns for TRACE and Hinode are discussed.

Authors: Aveek Sarkar, Robert W Walsh
Projects:

Publication Status: ApJ(accepted)
Last Modified: 2008-04-22 16:29
Go to main E-Print page  Edit Entry  Download Preprint  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
Simulating coronal loop implosion and compressible wave modes in a flare hit active region
Modeling solar coronal bright point oscillations with multiple nanoflare heated loops
EUV Observational consequences of the spatial localisation of nanoflare heating within a multi-stranded atmospheric loop
Subject will be restored when possible
Subject will be restored when possible
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