Beirut Port explosion a study showing how the atmosphere was affected by it Beirut Port explosion a study showing how the atmosphere was affected by it

Beirut Port explosion a study showing how the atmosphere was affected by it

Beirut Port explosion a study showing how the atmosphere was affected by it

About three and a half years after the Beirut Port explosion , a study by researchers from Wuhan University in China, in cooperation with researchers from Kocaeli University in Turkey, revealed the “temporary” disturbances caused by the explosion in the “ionosphere” layer of the Earth’s atmosphere.

The “ionosphere” is a region in the Earth’s upper atmosphere that extends from about 30 miles (48 kilometers) to 600 miles (965 kilometers) above the Earth’s surface. It consists mainly of charged ionized particles due to the influence of solar radiation, and it plays a decisive role in various atmospheric and electromagnetic phenomena.

Two studies prior to the Wuhan University study dealt with the impact of this layer on the explosion. One of them was an Indian-Japanese study published in the journal Scientific Reports, and the other was an American study published in the journal Radio Science, and they focused on the effect of the “sound waves” left by the explosion on the atmosphere in specific directions.

But what is unique about the new study published in the journal “Pure and Applied Geophysics” is that it provided more comprehensive data, as it included what happens in different directions as a result of the “ionosphere” layer being affected by sound waves, and other waves known as “acoustic gravity.”

Sound waves and acoustic gravity...what's the difference?
The lecturer in the “Geomatics” Department at the Faculty of Engineering in Shubra, Benha University in Egypt, a postdoctoral researcher at Wuhan University in China, and the main researcher of the study, Mohamed Freisheh, explains the difference between the two waves, in an interview with “Al Jazeera Net” via the “Zoom” application, as follows:

Sound waves
They are mechanical waves that spread through a medium (usually air) due to the sudden release of energy during an explosion event. These waves are transmitted through the atmosphere to the Earth in the form of longitudinal waves, in several steps:

Generation: The explosion generates a rapid and large amount of energy within a short period, and this leads to the creation of a pressure wave that spreads outward from the center of the explosion in all directions.
Diffusion: The pressure wave resulting from the explosion travels through the surrounding medium, which is the air. As the pressure wave travels, it compresses and decompresses (decompresses) the air molecules in its path.
Interaction of medium: Sound waves need a medium to propagate, air serves as the medium, and compressed air molecules transmit the energy of the pressure wave by colliding with neighboring molecules, and transfer momentum and pressure along the wavefront.
Effect: The pressure wave resulting from sound waves appears in the Earth’s atmosphere minutes after the explosion, and moves outward in all directions from the explosion site. Its spread is limited and not regional. The speed at which it travels through the atmosphere depends on various factors, including the degree of Temperature, humidity, and altitude. In dry air at room temperature, sound waves usually travel at a speed of about 343 meters per second (about 1,125 feet per second).
Detection: Sound waves resulting from explosions can be detected by various instruments, including infrasonic sensors and seismometers. These devices measure fluctuations in air pressure resulting from the passage of sound waves, allowing researchers to analyze the characteristics of the waves and determine the source and intensity of the explosion.
Acoustic gravitational waves
It is a unique combination of sound waves and gravitational waves, hence the term “acoustic gravity.” These waves travel through the atmosphere to the Earth, in several steps:

Generation: Acoustic gravitational waves are generated when a sudden, energetic event - such as a large explosion - disturbs the atmosphere. This disturbance creates waves that have the properties of both sound waves and gravitational waves.
Propagation: These waves propagate through the atmosphere and exhibit characteristics of both longitudinal (sound-like) and transverse (gravity-like) waves.
Effect: The effect of these waves appears in the Earth’s atmosphere about two hours after the explosion, and unlike sound waves, acoustic gravitational waves can have a regional effect, as they travel long distances through the atmosphere, maintain their energy and cohesion over large distances, and can spread at the speed of sound. Or faster, depending on the medium and the energy of the event.
Detection: Like sound waves, these waves can be detected by infrasonic sensors and seismometers.

Where did the researchers get the data?
To study the impact of the atmosphere on sound waves and acoustic gravitational waves resulting from the Beirut Port explosion, the researchers used data from Turkish reference stations for continuous monitoring and the Global Positioning Systems (IGS) service.

These services provide high-quality data from a global network of GNSS stations, including GPS, and other satellite navigation systems such as GLONASS, Galileo, and Beidou. These stations continuously monitor signals issued by satellites in orbit, providing precise location, timing, and weather data.

The signals of these stations are affected by the Earth's atmosphere, especially the ionosphere, as changes resulting from explosions such as electron density can cause delays and distortions in those signals, which allows researchers to detect abnormal events affecting that layer.

Freisheh explains that in high-energy explosions - such as the Beirut port bombing, which is described as "the largest non-nuclear explosion in modern history" - a large number of electrons may be liberated from atoms and molecules, which in turn contribute to ionizing the surrounding medium (air), which affects its electrical conductivity. Its thermal properties, and the presence of ionized particles can affect the behavior of acoustic gravitational waves as they propagate through the ionized region.

Experiment with 4 methods of data analysis
Because the activity of the Earth's atmosphere varies between the tropical, polar, and mid-latitude regions, due to differences in temperature, pressure, and humidity, the behavior of these waves varies from one place to another, and therefore the scientific tools used to study this behavior differ from one place to another. The method in which It gives accurate results in one place that may not be suitable in another place.

Freisheh says: “We tried four scientific tools to analyze the data, and concluded that the Savitzky-Golay method was the best and most appropriate for the conditions of the explosion that occurred in the country of Lebanon, which belongs to the mid-latitude regions.”

The four tools are: “Calculating Differences from Multistep Numericals,” “Sixth-Degree Polynomials,” and “Calculating Differences from Averages for a Week,” leading to the fourth method that the researchers found to be the most accurate, which is “Savitzky-Golay Smoothing Filter.”

The differences between the four methods can be explained as follows:

Calculating differences of multi-step numerical:
It involves measuring differences in what is known as the “vertical component of gravity” between two or more points on the Earth’s surface, and then combining these differences to calculate changes in the gravitational field.
 Sixth degree polynomials:
It is a mathematical function used to approximate a set of data points with the aim of finding a curve that closely matches the observed data, and can be used to extrapolate what happened.

Calculate variances from averages for a week:
It is a statistical measure used to analyze trends or patterns in data over time, specifically the average difference between the values ​​observed in the data set and the corresponding values ​​from one week ago.

Savitzky Golay smoothing filter:
It is a widely used signal processing and data analysis technique to reduce noise in data sets with repetitive patterns. The filter was developed by scientists Abraham Savitsky and Marcel J. E. Golay in the 1960s.

How does the Savitzky-Gulay method work?
In a previous study published in the journal Annals of Geophysics, Freisheh and his colleagues demonstrated that the first three methods can be inaccurate for various reasons, including that they do not deal with low-frequency disturbances, while some of them can be the result of abnormal events, and some of them bypass the disturbance. Which can be discovered, because it takes a certain period of time as an average to measure what comes after it and what comes before it, and it is possible for disturbance to occur in the time period between them.

“In our new study, the shortcomings of these methods were confirmed, and the Savitzky-Golay smoothing filter was the most accurate in explaining the disturbances that occurred in the atmosphere after the Beirut explosion,” says Freishah.

He explains how to use this filter through several steps:

First: data collection
Collecting “electron content effect” data from satellite-based measurements or ground-based ionospheric monitoring stations, these data show how the electron content in the ionosphere changes over time.

Second: Reducing noise
Electron content forcing data often contain noise and fluctuations due to various factors such as atmospheric turbulence or measurement errors, and the Savitzky-Golay smoothing filter is used in these data to reduce this noise while maintaining the overall trend.

Third: Homogeneity
The Savitzky-Golay smoothing filter smooths the "Electron Content Effect" data by fitting a polynomial curve to the data points within a moving window. This process removes short-term fluctuations caused by noise, making it easier to see the long-term effects of explosions on electron content .

Fourth: Identify patterns
After the electron content data is smoothed, trends and patterns in the data are analyzed by looking for sudden increases or decreases in electron content that may be associated with explosions or other events.

Fifth: Comparative analysis
Electron content impact data are compared before and after known explosion events. This comparison allows us to know how explosions affect the electron content in the ionosphere, and how quickly the ionosphere returns to its normal state after the event.

3 results and 4 applications
By applying the Savitzky-Golay smoothing filter to the data they obtained, Freisheh explains that their results revealed the following:

First: The ionosphere responded to the intense explosion twice:
First: The effect occurred after the explosion within a few minutes, and the frequency was low, and this effect was caused by “sound waves.”
The second: The ionospheric disturbance occurred more than two hours after the explosion, with a high frequency compared to the first, and was caused by “acoustic gravitational waves.”
 Second: The speed of the waves in the northern direction of the explosion was slower than the waves in the western and southern directions, respectively.
Third: The data revealed that two large explosions occurred in the port of Beirut, the first was small, and the second was more severe.
Freisheh says: Our results are an important indication that ionospheric disturbances are affected by the activity of the acoustic gravitational wave resulting from the explosion, and not by other random events, which is useful in many applications, including:

Providing valuable information about the characteristics of explosions:
Analyzing the propagation of sound waves and acoustic gravitational waves through the Earth's atmosphere can provide valuable information about the characteristics of explosions, such as energy release, location, and timing. This information can help authorities determine the cause and source of explosions, and improve explosion detection and monitoring systems.

Monitoring nuclear explosions:
If causes that could cause an effect in the atmosphere, such as volcanoes, earthquakes, and explosions similar to what happened in the port of Beirut, are excluded, studying the relationship between explosions and what happens in the Earth’s atmosphere can be useful in tracking the occurrence of nuclear tests in some places.

Space notes:
Studying the interactions between waves generated by explosions and the Earth's atmosphere enhances the understanding of space weather phenomena, ionospheric perturbations and their impact on satellite communications and space navigation systems.

Atmospheric modeling:
Studying the interaction between explosions and the Earth's atmosphere provides insight into atmospheric dynamics, including acoustic energy transfer, pollutant dispersion, and atmospheric oscillations. This knowledge contributes to atmospheric modeling and improves our understanding of atmospheric processes and the environmental impacts of explosions.

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