GGOS Focus Area
Geodetic Space Weather Research
To put the aforementioned issues in a nutshell, the main objectives of the FA-GSWR are the
- development of improved ionosphere models,
- development of improved thermosphere models,
- study of the coupled processes between the thermosphere and the ionosphere,
- improved understanding of space weather events and their monitoring by space observations (geodetic and non-geodetic).
The first objective aims at the high-precision and the high-resolution (spatial and temporal) modelling of the electron density. This finally allows to compute a signal propagation delay, which will be used in many geodetic applications, in particular in positioning, navigation and timing (PNT). Moreover, it is also important for other techniques using electromagnetic waves, such as satellite- or radio communications. Concerning the second objective, satellite geodesy will obviously benefit when working on precise orbit determination (POD), but there are further technical matters like collision analysis or re-entry calculation, which will become more reliable when using high quality thermosphere models. The third objective links the first two objectives by introducing physical laws and principles such as continuity, energy and momentum equations and solving partial differential equations. The fourth objective finally connects the improved understanding to the monitoring techniques and vice versa. Figure 2 visualizes the structure of the FA-GSWR as a double tetrahedron including the magnetosphere which is the region of the space around the Earth where the dominant magnetic field is the Earth’s magnetic field, rather than the IMF.
Figure 2: Structure of the IAG GGOS Focus Area on Geodetic Space Weather Research including the components Magnetosphere, Plasmasphere, Ionosphere and Thermosphere
Figure 3: Space-geodetic observation techniques and selected solar observation missions which provide valuable information about the MIT system
For a long time geodesists looked at the ionosphere just as a disturbing factor, whose impacts on electromagnetic signal propagation, i.e. the signal delay and the bending of the ray path, have to be corrected by applying ionospheric correction models of sufficient accuracy. On the other hand, as already mentioned before and shown in Fig. 3, the observation data of various geodetic measurement techniques that are influenced by the atmosphere in different ways provide valuable information on state and dynamics of the ionosphere. These are of great interest also for other disciplines such as meteorology.
Today, for Geodetic Space Weather Research geodesy has to go another step forward by introducing physics. To be more specific, we have to take into account the complete chain of cause and effect. This means the research has to start with processes and events on the Sun. Next, it has to continue with the effects in the near-Earth space and finally it has to consider the impact on (geodetic) applications and systems. Besides this general chain of cause and effect interactions, physics and especially the coupled processes within the MIT system have to be regarded. Geodetic Space Weather Research is fundamental research, too, particularly when intending to detect and to survey structures of the ionosphere, e.g. bubbles, or when studying special phenomena like electro-jets. Summarizing, geodetic space weather research has to be based on
a) the use and combination of all space geodetic observation methods,
b) the use of Sun observations,
c) real-time modelling,
d) the development of deterministic and stochastic forecast approaches,
e) assimilation strategies.