A modified forecast method of ionosphere VTEC series based on ARMA model

The ordinary ARMA forecast model uses the differential method to get the stationary ionosphere VTEC (Vertical Total Electron Content Unit) series. This paper proposes a new un-difference method to stabilize the VTEC time series. The superiority and reasonability of the new method is proved by comparing the result of two methods. Then, the un-difference predicting method is used to process the long series of IGS ionosphere VTEC products in this paper. By calculating the predicting result of the 263th day to 272th day from 2006 to 2015, this paper comes to conclusions that the predicting precision is higher during solar inactive years and lower during solar active years. The difference of the predicting precision can be used to distinguish the activity level of ionosphere.