Function: t89 Purpose: generates an array of model magnetic field vectors from a monotonic time series and an array of 3-d position vectors Keywords: tarray: N array representing the time series in seconds utc since 1970 rgsm_array: Nx3 array representing the position series in earth radii GSM kp(optional): the requested value of the kp parameter(default: 2) kp can also be an array, if it is an array it should be an N length array(you should interpolate your values onto the tarray) Also kp values passed in can only be integers. any pluses or minuses will be ignored, because the Tsyganenko model ignores plus and minuses on kp values period(optional): the amount of time between recalculations of geodipole tilt and application of a new kp value in seconds,increase this value to decrease run time(default: 600) igrf_only(optional): Set this keyword to turn off the t89 component of the model and return only the igrf component add_tilt: Increment the default dipole tilt used by the model with a user provided tilt in degrees. Result will be produced with TSY_DEFAULT_TILT+ADD_TILT Value can be set to an N length array an M length array or a single element array. N is the number of time elements for the data. M is the number of periods in the time interval.(determined by the period keyword) If single element is provided the same correction will be applied to all periods. If an N length array is provided, the data will be re-sampled to an M length array. Consequently, if the values change quickly, the period may need to be shortened. get_tilt: Returns the dipole_tilt parameter used for each period. Returned value has a number of elements equal to the value returned by get_nperiod set_tilt: Alternative alternative dipole_tilt value rather than the geopack tilt. This input can be an M length array, and N length array or a single elemnt. Value can be set to an N length array an M length array or a single element array. N is the number of time elements for the data. M is the number of periods in the time interval.(determined by the period keyword) If an N length array is provided, the data will be re-sampled to an M length array. Consequently, if the values change quickly, the period may need to be shortened. set_tilt will cause add_tilt to be ignored. get_nperiod: Returns the number of periods used for the time interval= ceil((end_time-start_time)/period) geopack_2008 (optional): Set this keyword to use the latest version (2008) of the Geopack library. Version 9.2 of the IDL Geopack DLM is required for this keyword to work. Returns: an Nx3 length array or -1L on failure Example: mag_array = t89(time_array,pos_array) mag_array = t89(time_array,pos_array,kp=5,rlength=10) Notes: 1. Relies on the IDL/Geopack Module provided by Haje Korth JHU/APL and N.A. Tsyganenko NASA/GSFC, if the module is not installed this function will fail. 2. Sums the contribution from the internal field model and the external field model. 3. Has a loop with number of iterations = (tarray[n_elements(t_array)]-tarray[0])/period This means that as period becomes smaller the amount time of this function should take will grow quickly. 4. Position units are earth radii, be sure to divide your normal units by 6374 km to convert them. $LastChangedBy: egrimes $ $LastChangedDate: 2014-03-19 08:22:59 -0700 (Wed, 19 Mar 2014) $ $LastChangedRevision: 14600 $ $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/spdsoft/trunk/external/IDL_GEOPACK/t89/t89.pro $