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.
(a modification of the Collisional Thick Target Model CTTM -Brown 1971)
Brown, Turkmani, Kontar, MacKinnon and Vlahos AA submitted
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
1. Beam density ~ coronal loop density
unless loop area there >> footpoint area
2. Very large no. Ne of e’s accelerated >> IP & radio Ne
Strong albedo bumps in HXR spectra - not observed.
Data => comparable upward and downward fluxes
(Kontar and Brown 2006)
Regardless of model, observed HXR flux fixes required value of source nonthermal EM
For a large HXR event
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
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
Thick Target Model (LRTTM)