This folder contains subfolders for the year 2015 with time domain raw data from the Sierra Nevada ELF station. Each year contains folders for each month, named with the four digits corresponding to year and month, e.g., 1512 stands for the raw data during December 2015. Within each month folder, the data and information files for each sensor and each hour are available. Data are stored in files containing measurements corresponding to a time period of approximately one hour. The filenames begin with a common part, “smplGRTU1_sensor_”, followed by a specific part to denote the sensor used (0 for the NS orientation and 1 for the EW orientation), the date and the initial time of the measurement recorded. For example, smplGRTU1_sensor_0_1412010430, stands for data measured by the NS-oriented magnetometer, in the year 2014, month 12, day 01, hour 04, and starting minute, 30. The information file has the same name but ends with _info.txt. Since the initial time is not fixed, the filenames in each folder are not completely determined. For this reason, each month folder includes two files, 'ficheros0' and 'ficheros1', that contain the set of filenames for that month. Therefore, for each normally measured we have 24 data files and also 24 information files for each sensor. Each hour data file occupies 1.8 MB, so each month has roughly a data volume of 2.6 GB.