FUNCTION dustem_plugin_synchrotron,key=key $
                                   ,val=val $
                                   ,scope=scope $
                                   ,paramtag=paramtag $
                                   ,paramdefault=paramdefault $
                                   ,help=help

;+
; NAME:
;    dustem_plugin_synchrotron
;
; PURPOSE:
;    DustEMWrap plugin to compute synchrotron emission
;
; CATEGORY:
;    DustEM, Distributed, Mid-Level, Plugin
;
; CALLING SEQUENCE:
;    synch=dustem_plugin_synchrotron([,key=][,val=])
;
; INPUTS:
;    None
;
; OPTIONAL INPUT PARAMETERS:
;    key  = input parameter number
;        1: s, power spectrum of CR E distribution
;         2 : Amplitude []
;         3 : polarization fraction [%] (default=0)
;         4 : polarization angle [deg]
;    val  = input parameter value
;
; OUTPUTS:
;    synch = synch spectrum (on dustem wavelengths)
;
; OPTIONAL OUTPUT PARAMETERS:
;    scope = scope of the plugin
;    paramdefault = default values of parameters
;    paramtag = plugin parameter names as strings
;
; ACCEPTED KEY-WORDS:
;    help                  = if set, print this help
;
; COMMON BLOCKS:
;    None
;
; SIDE EFFECTS:
;    None
;
; RESTRICTIONS:
;    The DustEMWrap IDL code must be installed
;
; PROCEDURE:
;    This is a DustEMWrap plugin
;
; EXAMPLES
;    dustem_init
;    vec=dustem_plugin_sychrotron(scope=scope)
;
; MODIFICATION HISTORY:
;    Written by JPB 2022 
;    Evolution details on the DustEMWrap gitlab.
;    See http://dustemwrap.irap.omp.eu/ for FAQ and help.  
;-

IF keyword_set(help) THEN BEGIN
  doc_library,'dustem_plugin_synchrotron'
  output=0.
  goto,the_end
ENDIF

;default values of input parameters
s=3           ;power spectrum of CR E distribution
A=1           ;Synchrotron radiation amplitude at 10 mm
psi=0.        ;default polarization angle
smallp=0.3;0.3    ;default polarization fraction
;scope='ADD_SED+ADD_POLSED'
scope='ADD_SED'
;paramtag=['s (plaw_index)','Amp','p','Psi (deg)']
paramtag=[textoidl('\alpha_{CR}'),'Amp','p',textoidl('\psi')+' [deg]']
paramdefault=[s,A,smallp,psi]
IF keyword_set(key) THEN BEGIN 
  
  ind1=where(key EQ 1,count1)
  ind2=where(key EQ 2,count2)
  ind3=where(key EQ 3,count3)
  ind4=where(key EQ 4,count4)
  
  IF count1 NE 0 then s=val[ind1[0]]
  IF count2 NE 0 then A=val[ind2[0]]
  IF count3 NE 0 then smallp=val[ind3[0]] 
  IF count4 NE 0 then psi=val[ind4[0]]
  
ENDIF

lambir=dustem_get_wavelengths()
Nwavs=n_elements(lambir)

cmic=3.e14
nu=cmic/lambir
lambir_ref=10000.

output=fltarr(Nwavs,3)

;following eqn is Deschenes et al 2008, eq 6
;output[*,0]=nu^(-(s+3.)/2.)

; following is Condon 1992 page 590 (in text)
output[*,0]=nu^((1.-s)/2.)

norm=interpol(output[*,0],lambir,lambir_ref)
output[*,0]=A*output[*,0]/norm

polar_ippsi2iqu,output[*,0],Q,U,replicate(smallp,Nwavs),replicate(psi,Nwavs)
output[*,1]=Q
output[*,2]=U

;stop

the_end:
RETURN,output
  
END