Alert on Strong Geomagnetic Storming and How Lonospheric Activity Impact on GNSS Performance

The 23 March CME arrived at around 24/1411 UTC. Severe (G4) geomagnetic storming has been observed and is expected to continue through the remainder of the 24 March-UTC day and into the first half of 25 March. The alert issued by NOAA's Space Weather Prediction Center in Boulder, Colorado.


image from NASA


The CME process occurred almost directly opposite the Earth, so when viewed from the Earth, the ejection formed a circular surface, which is what we mentioned in the past as the "full halo". The solar material ejected by such explosive activities is faster than the earth and has a high coverage, which may cause relatively strong geomagnetic activity.


Geomagnetic storms will interfere with communications and navigation. The main reason is that the ionizing radiation during geomagnetic storms will interfere with the ionosphere of the earth's atmosphere, causing ionospheric scintillation and ionospheric delay, which will in turn affect radio communications and navigation and positioning systems, resulting in Positioning error or interruption. For users who rely on GNSS for navigation and positioning, especially high-precision applications, operating activities should be reasonably arranged.


In addition to geomagnetic storms that affect ionospheric activity, periodic solar activity also has a huge impact on ionospheric activity, thereby affecting satellite positioning and navigation services.



Custom Icon    Introduction to Ionospheric Activity

The ionosphere is a region of Earth's upper atmosphere, extending from about 30 miles (48 kilometers) above the Earth's surface to several hundred miles in altitude. It is a dynamic and ever-changing layer characterized by the presence of ionized or charged particles, primarily electrons and positively charged ions. These charged particles are created through the process of ionization, which is primarily driven by solar radiation. As solar energy reaches the Earth's upper atmosphere, it causes neutral gases to become ionized, leading to the formation of the ionosphere.


The ionospheric active cycle is usually associated with cyclic changes in solar activity, and the duration of a cycle is about 11 years. The current solar activity cycle is expected to peak between 2024 and 2026. Ionospheric activities will directly affect the propagation and reception of GNSS satellite signals, which may lead to a decrease in positioning accuracy. Generally speaking, ionospheric activity is more active at lower latitudes, so the impact on high-precision users around the equator may be more significant.

NOAA Space weather prediction center



Custom Icon    The Effects of Ionospheric Activity on GNSS Performance

Ionospheric activity, influenced by factors such as solar radiation and geomagnetic storms, can have several effects on GNSS performance. Understanding these effects is crucial for accurate positioning and navigation. Here are the key impacts of ionospheric activity on GNSS:


Signal Delay:

The ionosphere causes delays in GNSS signals as they pass through the ionized layers. Delay is frequency-dependent, with higher-frequency signals experiencing greater delays. This delay can lead to inaccuracies in the calculation of signal travel time, affecting position estimation.

Frequency Dispersion:

Higher-frequency GNSS signals, such as those in the L2 band, are more susceptible to ionospheric dispersion. Dispersion causes the different frequencies of the signal to travel at different speeds, leading to spreading and distortion of the signal. Frequency dispersion can result in inaccuracies in phase measurements and impact positioning accuracy.

Signal Scintillation:

Ionospheric scintillation refers to rapid fluctuations in signal amplitude and phase caused by irregularities in the ionosphere. Scintillation effects are more pronounced in equatorial and high-latitude regions. Scintillation can lead to signal loss, tracking errors, and increased uncertainty in GNSS measurements.

Geomagnetic Storm Impact:

Geomagnetic storms, triggered by solar activity, can intensify ionospheric disturbances. During geomagnetic storms, increased electron density in the ionosphere can lead to stronger signal delays and scintillation. Storm-induced disturbances may result in temporary GNSS service outages and degraded accuracy.



Custom Icon    Mitigating the Effects of Ionospheric Activity

Users are advised to consider the following recommendations when using GNSS positioning to fully utilize the latest algorithms and reduce the impact of ionospheric activity:


Updating Receiver Firmware:

Ensure that the receiver firmware is updated to the latest version to optimize positioning performance during ionospheric activity using the latest algorithms.

Using Dual-Frequency or Triple-Frequency Receivers:

Dual-frequency or triple-frequency receivers can utilize signals of different frequencies to calculate and correct ionospheric delays, thereby improving positioning accuracy.

Utilizing Multiple Satellite Systems:

In addition to the GPS system, consider using satellite signals from other GNSS systems such as GLONASS, Galileo, BeiDou, etc. Using multiple satellite systems can increase the amount of observation data, enhancing positioning reliability and accuracy.

Adjusting Satellite Elevation Angle:

Setting the satellite elevation angle to 10 degrees can reduce the impact of the ionosphere on satellites closest to the horizon. Setting a higher satellite elevation angle can mitigate signal propagation delays caused by the ionosphere.

In summary, by implementing measures such as updating receiver firmware, using dual-frequency or triple-frequency receivers, utilizing multiple satellite systems, and adjusting satellite elevation angles, users can better address positioning errors during ionospheric activity, thereby improving the accuracy and reliability of GNSS positioning.





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