pro read_dst,filename,time=time,value=value,max_days=max_days

;+
;read the hourly DST index from the standard text data file provided
;by NOAA/NGDC
;
;History
; 2004/12/09     Jie Zhang      created
;-

if not keyword_set(max_days) then max_days= 366 ; holding maximum one year's data (366)
date_str   = STRARR(max_days)    ; date in DSTYYMM*DD
dst_ind    = INTARR(24,max_days) ; DST index, one-hour averaged, 24 per day
line=''
i=0

; Read in the index file

OPENR,lu,filename,/get_lun
WHILE (not eof(lu)) DO BEGIN
    READF,lu,line
    IF (strmid(line,0,1) ne '#') THEN BEGIN
        date_str[i]=strmid(line,0,10)
        
        READS,strmid(line,16,104),tmp1,tmp2,tmp3,tmp4,tmp5,tmp6,tmp7,tmp8,tmp9,tmp10,tmp11,tmp12,tmp13,tmp14,tmp15,tmp16,tmp17,tmp18,tmp19,tmp20,tmp21,tmp22,tmp23,tmp24,tmp25,tmp26,FORMAT='(26i4)'
        dst_ind[0,i]=tmp2
        dst_ind[1,i]=tmp3
        dst_ind[2,i]=tmp4
        dst_ind[3,i]=tmp5
        dst_ind[4,i]=tmp6
        dst_ind[5,i]=tmp7
        dst_ind[6,i]=tmp8
        dst_ind[7,i]=tmp9
        dst_ind[8,i]=tmp10
        dst_ind[9,i]=tmp11
        dst_ind[10,i]=tmp12
        dst_ind[11,i]=tmp13
        dst_ind[12,i]=tmp14
        dst_ind[13,i]=tmp15
        dst_ind[14,i]=tmp16
        dst_ind[15,i]=tmp17
        dst_ind[16,i]=tmp18
        dst_ind[17,i]=tmp19
        dst_ind[18,i]=tmp20
        dst_ind[19,i]=tmp21
        dst_ind[20,i]=tmp22
        dst_ind[21,i]=tmp23
        dst_ind[22,i]=tmp24
        dst_ind[23,i]=tmp25
        i=i+1
    ENDIF
    if i ge max_days then break
ENDWHILE
FREE_LUN,lu

day_num=i
;print,'valid day=',day_num
if day_num gt 0 then begin
;   Truncate the array to include only valid points
date_str = date_str(0:day_num-1); print the date of Dst 
dst_ind = dst_ind(*,0:day_num-1); print the value of Dst interger
value=fltarr(24*day_num) ; print value of Dst in float

;convert the data into a single array, the time into a single UTC array
time_str=STRARR(24*day_num)
for i=0,day_num-1 do begin
    for j=0,23 do begin 
 ;      if (strmid(date_str[i],3,2) gt 10) then yy='19' else yy='20'    ;year 2000 problem
	yy='20'
       tmp_str=yy+strmid(date_str[i],3,2)+'/'+strtrim(strmid(date_str[i],5,2),2)+'/'+strtrim(strmid(date_str[i],8,2),2)+' '+strtrim(string(j+1),2)+':00'
       time_str(i*24+j)=tmp_str
       value(i*24+j)=dst_ind(j,i)
    endfor
 endfor

;stop

time=str2utc(time_str)
endif

RETURN

END