Data are stored in the JSOC in "Data Series" and you need to use the correct format to access it. All HMI data have the prefix "hmi.". Similarly, all AAI data have the prefix "aia"; MDI data have the prefix "mdi", SHA data have the prefix "sha."and IRIS data have the prefix "iris".The typical data format is the series name followed by the data and time. For example: hmi.M_45s[2011.01.01_01:30:00_TAI/30m] refers to the LOS Magnetograms on the date 2011/01/01 at time 01:01:30_TAI for an interval of the next 30 min. Similarly, hmi.Ic_45s[2011.01.01_01:30_TAI-2011.01.01_02:00_TAI]. This query requests all HMI continuum data for January 1, 2011 between 01:30 and 02:00 TAI.
The data series archived in JSOC are enumerated here
More details about data products can be found in the left hand navigation bar on this page. For more information on the JSOC, see the wiki
If you know which instrument and data product you would like to access, but do not know what the series name is called go to Mapping dataproducts to Series see