- High solar activity: what impact will it have on your GNSS device?
- High solar activity: what impact will it have on your GNSS device?
- High solar activity: what impact will it have on your GNSS device?
- High solar activity: what impact will it have on your GNSS device?
- High solar activity: what impact will it have on your GNSS device?
- High solar activity: what impact will it have on your GNSS device?
- High solar activity: what impact will it have on your GNSS device?
- High solar activity: what impact will it have on your GNSS device?
- High solar activity: what impact will it have on your GNSS device?
- High solar activity: what impact will it have on your GNSS device?
High solar activity: what impact will it have on your GNSS device?
EMINENT APPROACH
SOLAR MAXIMUM
Recently our Sun emitted a powerful eruption. It is an impressive phenomenon. These geomagnetic storms cause major disruption to the electronic equipment we use every day: satellites, telecommunications and geolocation networks, etc
What are the real consequences for GNSS measurement equipment? How can we prevent disruption and continue surveying in the field?
SOLAR ACTIVITY
As with any star, the Sun is constantly active, regularly expelling huge jets of matter known as solar flares.
The Sun has what is known as a ” solar corona “, made up of plasma, a completely ionised gas whose temperature is higher than that of its surface. During solar flares, jets of plasma, magnetic waves and charged particles are expelled into interstellar space at speeds of up to 2,000 kilometres per second.
Solar flares vary in power and duration from a few minutes to a few hours. The impact on our planet depends on their intensity. For this reason, space weather services are responsible for monitoring and assessing them.
SOLAR FLARE MEASUREMENT SCALE
Solar flares are assessed according to their intensity (watts/m²) on a scale equivalent to the Richter scale in seismology.
They are classified into six categories, A, B, C, M and finally X and X10 for the most powerful (the solar flare of 1859 known as the Carrington Event). Each category corresponds to an intensity 10 times greater than the previous one. To this alphabetical value is added an identity coefficient ranging from 1 to 9.
Powerful solar flares in the M and X classes can cause coronal mass ejections (CMEs). CMEs have their own magnetic fields. CMEs can then cause magnetic field disturbances. When they are directed towards the Earth, they can have effects on our planetary environment.
CORONAL MASS EJECTION, SOLAR STORM
Coronal mass ejections (CMEs ), more commonly known as solar storms. CMEs are plasma bubbles that are often triggered by a strong solar flare.
These giant bubbles modify the atomic characteristics of the solar wind. The solar wind moves through interstellar space in all directions, including the Earth.
The magnetic field of the solar storms (EMC) is very strong. When the ejecta head towards Earth, their magnetic fields interact with our magnetic shield (Earth’s magnetosphere). The magnetic reconnection of the two fields causes geomagnetic storms. The Earth’s field lines are compressed to the point where they open up. This reaction weakens our magnetic shield.
Weakened, our shield becomes temporarily permeable to certain solar emissions. When one coronal mass ejection follows another in the direction of the Earth, the effects on the terrestrial environment and our technological equipment can be very significant.
In general, the vast majority of particles emitted by solar winds are blocked by the Earth’s magnetic field and therefore have no impact. This phenomenon is visible on Earth in areas near the poles and is known as the “polar aurora”.
However, since the beginning of the year, the Sun has been experiencing coronal mass ejections (CMEs) on an almost daily basis, according to the National Oceanic and Atmospheric Administration. And the frequency will continue to increase. Why is this?
THE SOLAR CYCLE
Like the Earth, the Sun is subject to a rhythm of seasons that follow one another almost constantly. This is known as the Solar Cycle, and its average duration is 11.2 years (varying between 9 and 25 years).
One of the criteria for determining the progress of the solar cycle is the number of sunspots visible on the surface of the Sun. There are few in the Solar Minimum and many in the Solar Maximum.
Sunspots are the result of intense magnetic activity. This activity is so powerful that it slows down the convection (circulation) of matter and reduces the heat influx to the Sun’s surface. As a result, some zones become less hot than others. This is why we can observe a difference in contrast at the surface of our star. When there are a lot of sunspots, there are a lot of flares and solar storms.
During solar maximum, solar storms are at their peak. There is a high probability of the appearance of M and X category solar storms.
We are currently close to Solar Maximum, which should be reached between 2023 and 2025. Solar storms and ejections will therefore be very active. Only a small proportion of solar storms are Earth-bound. However, the impact on our environment can still be considerable.
Below is a graph highlighting the variations in solar activity over the eleven-year solar activity cycle. The estimated and anticipated values are shown in red, while the actual values measured monthly are shown in black.
SOME OF THE CONSEQUENCES OF SOLAR FLARES
1859
The Carrington event is known today as the largest geomagnetic storm ever recorded (greater than category X10). It disrupted telegraph services in North America and Europe. Some accounts indicate that telegraph lines were energised without any electrical source, that operators were electrocuted or that some telegraph lines caught fire. If this event had taken place today, the consequences would have been far greater.
1989
The most intense EMCs can produce telluric currents in long power lines, generating voltages and currents of considerable intensity that can exceed the safety thresholds of network equipment. In 1989 and 2003, telluric currents caused local blackouts.
5, 6, 13 and 14 December 2006
Signals from the GPS satellite network were severely disrupted for several hours by gigantic coronal mass ejections, the most intense of which was measured at X9.
5 April 2010
A solar flare disrupted the trajectory of an orbiting telecommunications satellite, cutting off all communication with the control station. IntelSat’s Galaxy 15 satellite became uncontrollable.
17 April 2015
A coronal mass ejection of category M1.05 caused magnetic storms that affected PPP and RTK services in Norway. During this event, known as the St Patrick’s Storm, a significant drop in accuracy was observed. This is thought to be due to the sharp drop in the number of positioning satellites taken into account following disturbances in the ionospheric layer.
4 February 2022
40 of the 49 satellites launched by the SpaceX programme did not reach their orbits and were destroyed in the atmosphere.
March 2022
A radio blackout caused by an X-class solar flare affected the Americas, South-East Asia and Australia.
More generally, a strong solar storm can cause :
Overloading of electricity transformers causing blackouts
Damage to satellites in high orbit
Disruptions to the time-stamping of financial transactions
Passenger radiation during air travel
Disruption of telecommunications signals
Space weather enables us to anticipate the Sun’s mood and provide solutions to limit its impact.
IMPACT ON GNSS DEVICES
As mentioned above, the solar wind and ejections of ionised mattercause magnetic reconnections when they reach the Earth’s magnetosphere. This interaction is the source ofmagnetic storms.
These magnetic storms occur in theionosphere, the atmospheric layer in which satellites operate and from which telecommunications and geolocation signals are transmitted.
Solar activity therefore causes fluctuations in the ionosphere, leading to numerous malfunctions in electronic equipment, including GNSS equipment. GNSS equipment receives signals through this disturbed atmospheric layer.
In addition to the impact of magnetism on the equipment itself, signal delay due to the ionosphere is one of the main sources of error in GNSS. Sudden disturbances of this atmospheric layer make it a subject of major importance.
Monofrequency devices
A single-frequency GNSS (commonly known as GPS) device calculates its position by triangulation using a single frequency (L1) emitted by several satellite constellations(see our article “GNSS – how it works”).
To correct errors caused by signals passing through the ionosphere, single-frequency receivers incorporate a model of the ionosphere, which may prove inadequate during sudden magnetic storms.
As a result, receiver accuracy can be severely degraded and in some cases it becomes impossible to fix ambiguities even on short baselines.
Dual-frequency equipment
For several years now, GNSS equipment has been improved by the use of a second signal (L2). With dual-frequency operation, it is no longer necessary to use an ionospheric model. By linear combination, it is possible to use a so-called ion-free frequency to resolve ambiguities. This means there are fewer errors to correct when calculating position. The device can then provide accurate positioning.
Although the issue of modelling the ionosphere has been resolved, another remains, that of ‘scintillation’: strong solar flares, such as CMEs, can generate rapid changes in the phase and amplitude of signals. This significant scintillation in the low frequencies can cause certain satellites to reject the signal , resulting in a loss of accuracy or the cessation of the device’s positioning service.
Practical consequences in the field
During an EMC, there will be a significant loss of accuracy at the beginning and end of the magnetic storm episode. At the height of the storm, geolocation solutions will probably be lost. All receivers continue to be affected by ionospheric disturbances. Dual-frequency receivers are much more accurate than single-frequency receivers.
In practical terms, ionospheric fluctuations prevent a GNSS receiver from fixing ambiguities. Even if the receiver uses an accuracy enhancement service, it remains in RTK Float mode and can only achieve decimetre accuracy.
Today, many consumer products are single-frequency. They are dual-frequency for entry-level and mid-range professional measurement equipment.
As mentioned, ionospheric disturbances will continue to increase over several years, with a solar maximum in 2024-2025, so it is important to anticipate this element in the field and provide a solution.
SOLUTIONS
The ionospheric disturbance is a one-off phenomenon. It mainly affects measurements in the middle of the day, when the disturbances are most intense. The scale of the disturbance is relatively small compared with disturbances measured at the magnetic equator.
If you have a single- or dual-frequency instrument, we therefore recommend that you use it at the beginning and end of the day.
To help you identify the most favourable periods of use, TERIA offers you the option of checking the level of ionospheric disturbance in real time. To do this, you can observe the state of the ionosphere directly on this article using the module opposite, developed by our engineers.
You can also download the free iTERIA application for even greater convenience, so you can have this information at your fingertips at all times.
WHAT TO DO WHEN SURVEYS HAVE TO BE CARRIED OUT IN THE MIDDLE OF THE DAY?
A new generation of equipment has recently been introduced that uses several additional frequencies. Operating in tri-frequency mode , or even quadri-frequency mode in some constellations, they provide a crucial redundancy of information to correct errors caused by ionospheric disturbances. Using three or more frequencies makes it possible to identify and exclude any measurement errors. Extending the frequency range thus improves iono-free processing while reserving one frequency for monitoring.
The PYX by TERIA, which is equipped with a three-frequency GNSS card that can be upgraded to four frequencies, belongs to this latest top-of-the-range generation. Improved ambiguity resolution adds extra reliability to measurements. As a result, it is only slightly affected by ionospheric disturbances.
However, even if your device is new-generation, if it uses an N-RTK positioning service that is not :
- full GNSS multi-frequency,
- assisted by technical support,
- monitored by an audit and ongoing maintenance of the network to guarantee its integrity,
- continuously monitored, particularly for ionospheric activity.
So it’s important to check the technical specifications when you buy your GNSS mobile and to opt for an ISO-certified NRTK correction service. The quality of these two elements will allow you to work with complete peace of mind.
LES SOLUTIONS TERIA
TERIA is ISO-certified and meets these quality criteria. In addition to its network of more than 240 GNSS stations (in France), TERIA is also able to provide Full GNSS corrections in Europe on all the GNSS frequencies available through the associated constellations. Real-time monitoring on our servers enables us to warn of ionospheric events and alert users.
The PYX All-in-One package gives you a top-of-the-range made-in-France receiver with all its accessories, backed up by an ISO 9001 and 14001-certified NRTK service.
