Long-term ionospheric characteristics over Lhasa

It is important to study ionospheric characteristic for researching electron equipments impacted by ionosphere. There are important effects on the electron equipments for the variations of ionosphere, such as it can induce shortwave communications quality decline indeed interrupted, navigation signal scintilla and error increase, space probe orbit change, charge up and proton event etc. Based on Lhasa's data of ionospheric vertical sounders more than 30 years, we researched the daily variations, seasonal changes and long-term trends of the ionosphere of Lhasa, and get some meaningful conclusions. The annual means of ionospheric f_oF₂ are between 3-11 MHz, the daily changes of ionospheric f_oF₂ are significant, and the seasonal changes are also obvious, the f_oF₂ varies greatly with solar activities. The annual means of ionospheric h'F are between 200-420 km, the daily changes of ionospheric h'F are significant, and the seasonal changes are unconspicuous, there are positive correlation between h'F and solar cycle changes. The annual means of ionospheric f_oEs are between 1-7 MHz, the daily changes and the seasonal changes of ionospheric f_oEs are significant as well, yet the solar cycle changes are not noticeable. Studying the long-term variation of the ionosphere and obtaining the long-term change rule is important to the design and maintenance of communication navigation, spacecraft equipments.