Pro tr_plot_hlz, date, lowlat=lowlat, oval=oval, hc=hc
;
;NAME:  tr_plot_hlz
;        
;PURPOSE:
;       To compute magnetic latitude of the orbit and plot the times
;	of SAA, high latitude and passage through the auroral ovals for a day's
;	day's worth of timelineing (date 12:00 --> date+1 12:00)
;
;SAMPLE CALLING SEQUENCE:
;       tr_plot_hlz,'23-Jun-98', /hc
;	tr_plot_hlz,'23-Jun-98', lowlat=45, oval=[55,75], /hc
;
;INPUTS:
;	date - date of the 24 hour period desired
;	lowlat - lower limit for high latitude region (default = 40 degrees mag)
;	oval - array of low and upper magnetic latitude limits for oval 
;	  boundaries (default = [50,70])
;	hc - set for hardcopy on default ps printer
;	Assumes North magnetic pole at latitude = 78.5 and longitude = -70
;OUTPUTS
;	4 plots covering 6 hours each; normally use /hc to get paper plots
;HISTORY:
;        Written 21-Jun-98 by TDT
;	 Changed  2-May-99 by TDT  plot 00:00 to 24:00, not 12 - 12
;#
if (not keyword_set(lowlat)) then lowlat=40.
if (not keyword_set(oval)) then oval=[50.,70.]
if (not keyword_set(hc)) then hc=0

doy=anytim2doy(date)
t1=doytim2ints(string(doy)+' 00:00')
t2=doytim2ints(string(doy)+' 06:55')
high_mag_lat,[t1,t2],lowlat=lowlat,oval=oval,hc=hc
t1=doytim2ints(string(doy)+' 06:00')
t2=doytim2ints(string(doy)+' 12:55')
high_mag_lat,[t1,t2],lowlat=lowlat,oval=oval,hc=hc
t1=doytim2ints(string(doy)+' 12:00')
t2=doytim2ints(string(doy)+' 18:55')
high_mag_lat,[t1,t2],lowlat=lowlat,oval=oval,hc=hc
t1=doytim2ints(string(doy)+' 18:00')
t2=doytim2ints(string(doy+1)+' 00:55')
high_mag_lat,[t1,t2],lowlat=lowlat,oval=oval,hc=hc
return
end