slide1
Download
Skip this Video
Download Presentation
A Local Reacceleration Thick Target Model (LRTTM)

Loading in 2 Seconds...

play fullscreen
1 / 14

A Local Reacceleration Thick Target Model (LRTTM) - PowerPoint PPT Presentation


  • 56 Views
  • Uploaded on

A Local Reacceleration Thick Target Model (LRTTM) (a modification of the Collisional Thick Target Model CTTM -Brown 1971) Brown, Turkmani, Kontar, MacKinnon and Vlahos AA submitted. Collisional TTM. Acceleration. Collisional Transport NO Acceleration. Radiation only No accln.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' A Local Reacceleration Thick Target Model (LRTTM) ' - kasa


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

A Local Reacceleration Thick Target Model (LRTTM)

(a modification of the Collisional Thick Target Model CTTM -Brown 1971)

Brown, Turkmani, Kontar, MacKinnon and Vlahos AA submitted

collisional ttm
Collisional TTM

Acceleration

Collisional

Transport

NOAcceleration

Radiation

only

No accln

the c ollisional t hick t arget m odel cttm brown 71 73 etc hudson 72 etc
The Collisional Thick Target Model CTTM Brown 71, 73 etc Hudson 72 etc

MERITS OF CTTM

Provides a ‘cartoon’ scenario for flare impulsive phase emissions roughly fitting observations

Collisional transport is easy to work with even though we know it cannot really be valid!

Separates acceleration site from HXR (TT Injection) source – ie no acceleration in HXR source. Simple but v restrictive

problems with cttm
PROBLEMS WITH CTTM
  • Inefficiency of bremss =>

1. Beam density ~ coronal loop density

unless loop area there >> footpoint area

2. Very large no. Ne of e’s accelerated >> IP & radio Ne

  • Downward beaming =>

Strong albedo bumps in HXR spectra - not observed.

Data => comparable upward and downward fluxes

(Kontar and Brown 2006)

  • Does not really tally with EM(t) and T(t) data
  • Beam driven evaporation does not work – self choking
hxr source requirements
HXR Source Requirements

Regardless of model, observed HXR flux fixes required value of source nonthermal EM

For a large HXR event

for any thick target model the n 1 source electrons of life t need replenished at a rate
For any thick target model the N1 source electrons of life t need ‘replenished’ at a rate

For the CTTM collisional case t =tcoll ~ 1/n and F 1 is independent of n

If there is LOCAL REACCELERATION inside the HXR source t is increased and F1reduced. In other words the photon yield per electron is increased

one candidate for the local reacceleration
ONE CANDIDATE FOR THELOCAL REACCELERATION –

ELECTRIC FIELDS IN CURRENT SHEET CASCADE OF DISTRIBUTED ENERGY RELEASE (Galsgaard…. Vlahos… Turkmani…..)

MHD defines stochastic electric fields

Test particle acceleration occurs in these in both the corona and then after injection to the chromosphere

slide8

CSC E fields

Corona

Chromosphere

electron motion

slide9

A Local Reacceleration

Thick Target Model (LRTTM)

some lrttm vs cttm properties
SOME LRTTM vs CTTM PROPERTIES
  • Needs lower electron flux and number (but as much beam power) as CTTM. How much lower depends on uncertain parameter values (resistivity etc). More consistent with radio and IP values.
  • Electrons much less anisotropic (less albedo)
  • Like CTTM, predicts HXR footpoints displaying rapid structure, syhnchronism and time of flight delays

BUT

  • Footpoint/coronal contrast higher than CTTM
  • MUCH higher proportion of beam power goes into chromosphere, and deeper – may help with evaporation and WLF problems
ad