v2.4 Changes


Features:
+ 20170328
+ Added IGRF_Tilt() function to return IGRF dipole tilt angle.

+ 20160811
+ Added keyword MLT2mlon to allow for inverse calculations, i.e., MLT to AACGM
  longitude. By setting this keyword the input parameter, mlon, is treated as
  MLT (decimal hours) and the AACGM_v2 magnetic longitude corresponding to
  that MLT is returned.

+ 20160525
+ allowed verbose keyword to AACGM function calls to be negative in order to
  suppress WARNING messages, in particular when the altitude is zero a WARNING
  is issued for negative height since the conversion to geocentric causes the
  height to become negative in the high-latitude. The height is small and the
  WARNING is annoying.

Bug fixes:

+ 20170201
+ fixed bug in function MLTConvertYrsec_v2(), array values not correct

  -   tmlt = MLTConvert_v2(yr[k],mo[k],dy[k],hr[k],mt[k],sc[k],mtmp, $
  +   tmlt = MLTConvert_v2(yrtmp,mo,dy,hr,mt,sc,mtmp, $

+ 20160816
+ added return in mlt_v2() and MLTConvert_v2() if mlon is NaN. Note that this
  also required some logic to deal with array input and the possibility of
  some values being NaN.

+ 20160525
+ fixed minor bug in call to mlt_v2. When yr keyword was specified and hr, mt
  or sc where set to 0 (a valid entry) the existing logic caused an error to
  be set and a NaN returned. The logic now requires only mo and dy to be
  specified if yr is set and an ERROR message now appears. hr, mt and sc are
  set to 0 if they are not specified as well.