# Observations of Gravity Wave propagation in the Equatorial Ionosphere after the Hunga Tonga-Hunga Ha'apai eruption with Ionosonde data and HYSPLIT Modeling

Lima Newton Silva De, Santos Alan Ferreira Dos, Filho Eriberto Barroso Façanha, Oliveira Liliam Gleyci de Souza, Oliveira Aldemir Malveira De, Silva Daniel Barros Valentim Mansur Da

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Lima Newton Silva De, Santos Alan Ferreira Dos, Filho Eriberto Barroso Façanha, Oliveira Liliam Gleyci de Souza, Oliveira Aldemir Malveira De, et al.. Observations of Gravity Wave propagation in the Equatorial Ionosphere after the Hunga Tonga-Hunga Ha'apai eruption with Ionosonde data and HYSPLIT Modeling. 1 (1), pp.36-46, 2022, Amazon Expedition Magazine V1 N1. hal-04001539

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<figure><img src="image_1.png" /></figure>

https://www.google.com/maps/Hunga+Tonga/@-20.569987,-175.3975096,14z/

# Observations of Gravity Wave propagation in the Equatorial Ionosphere after the Hunga Tonga-Hunga Ha'apai eruption with Ionosonde data and HYSPLIT Modeling

Newton Silva de Lima¹,², Alan Ferreira dos Santos¹, Eriberto Barroso Façanha Filho¹,², Liliam Gleicy de Souza Oliveira¹, Aldemir Malveira de Oliveira²,³, Daniel Barros Valentim Mansur da Silva⁴.

## (1) Lutheran University Center of Manaus - CEULM/ULBRA

Av. Carlos Drummund de Andrade, 1460. Conj. Atilio Andreazza - Japiim II - CEP 69077-730. Manaus, Amazonas - Brazil. Tel: (+55 92 3616-9800). Email: acsmao@ulbra.br

## (2) Secretary of State for Education and Sports of the State of Amazonas

Street: Waldomiro Lustosa, 250 - Japiim II, Manaus - Amazonas. Brazil. CEP 69076-830
Manaus, Amazonas - Brazil. https://www.seduc.am.gov.br/

## (3) University Center for Higher Education of Amazonas - CIESA

Rua Pedro Dias, 203 - Flores. CEP 69058-818 Manaus - Amazonas - Brazil. Tel. (+55 92 99401-6229).
Email: academico@ciesa.br

## (4) Martha Falcão College - Wyden

Rua Natal, 300 - Adrianópolis - Manaus - Amazonas - Brazil. CEP 69057-090. Tel.: (+55 (92) 2121-0929).

e-mail: newton.lima@ulbra.br; alan.ferreira@ulbra.edu.br; eriberto.filho@ulbra.br; liliam_gso@yahoo.com.br; amoliveira@gmail.com, danielvmansur@gmail.com.
**Abstract**

This article reports the propagation of gravity waves in the Ionosphere over the west coast of South America (-11.9523954; -76.8757172) as of 01:03 UTC, after the eruption of the Hunga Tonga-Hunga Ha'apai volcano (-20.8229 ; -175.4376) using Ionosonde (VIPIR) (PEZZOPANE and SCOTTO, 2005) and HYSPLIT Modeling for January 15, 2022 (17:00 UTC). It was observed the real accuracy of this instrumentation for the verification of gravity waves in the Equatorial Ionosphere.

**Keywords:** Layers F1, F2, F3, Es; Magnetic Equator; ionograms (VIPIR).

**Introduction**

In Lima (2009) and Lima et. al., (2011), he says that oscillating ionospheric disturbances such as gravity waves (GW) and traveling ionospheric disturbances (TID - Traveling Ionospheric Disturbances), are treated by some researchers as synonyms (KELLEY, 1989, HARGREAVES, 1992). TIDs, which are oscillations with a period on the order of hours to minutes, are produced in geomagnetic periods disturbed by the Joule effect at high latitudes and travel in the equatorial direction, while GW generally have their origins in the lower atmosphere by tropospheric winds, fronts cold weather or tropical convection (FAGUNDES et al., 2007) and according to Hines (1960), can also be caused by meteors entering the Earth's atmosphere, rocket launches in the F region of the ionosphere or by Solar Eclipse. In addition to nuclear explosion, volcanic eruption (FERREIRA et al., 2018; KOMJATHY et al., 2012, MINSTER, 1996; ROW, 1967). Hegai et al., (2006), investigated disturbances in the F2 region at mid-latitude during nighttime in the ionosphere that were produced by internal gravity waves generated before a strong earthquake through Joule heating due to the electric field of short duration seismogenics, in the Region D, of the ionosphere. Hines (1974) adds that GW originate by transfer of momentum and pressure and gravity gradients in an anisotropic medium.

During propagation of gravity waves in the neutral atmosphere, depending on the type of forcing in the ionospheric plasma, the time in the region of maximum anomaly (in this study, on the magnetic equator) the appearance of stratification for an F3 layer, is sometimes present. , a fact also discussed by Klausner and Fagundes (2005) and shown in Mendoza et al., (2021).

Fagundes et al., (2008) proposes to study gravity waves, through ionograms obtained by digital Ionsonde that simulate the same RADAR sounding, so sounding analyzes with high temporal resolution (100 seconds, for example) should be used. In Pillat and Guimarães, (2014), the technology and data acquisition by ionosondes are in the radio frequency range from 1 to 20-30 MHz. The radio frequency signals transmitted by ionosondes are reflected when the transmitted frequency is equal to the natural frequency of the ionospheric plasma, that is, the echoes return to the Earth's surface, whose graphs resulting from these echoes when performing a frequency sweep are called ionograms. In this work we use a digital Ionosonde composed of several antennas (Vertical Incidence Pulsed Ionospheric Radar – VIPIR), (MENDOZA et al., 2021, TSAI, et al., 2014), and HYSPLIT - (Hybrid Single Particle Lagrangian Integrated) modeling.

**Materials and Method**

**The site**

Observations were carried out between coordinates (-20.570; -175.398) and (-11.9523954; -76.8757172), near the center of the Equatorial Pacific Ocean and the west coast of South America over Peru, respectively.

**Gravity Waves (GW)**

Study the morphological aspects of the GW, that is, seasonal variation, preferential propagation direction, wavelengths, periods and characteristic propagation speed, mainly in the equatorial region of the event (January 15, 2022) with the aid of Trajectory, dispersion, deposition modeling and Ionograms, were performed in this observation. The dynamics of the lower and upper atmosphere, which were excited after the strong volcanic eruption of the Hunga Tonga-Hunga Ha'apai, mainly in the transport of momentum and energy through clouds of ash, steam and gas up to 30 km into the atmosphere at the beginning of the eruption, the plume that initially spread across 260 km in diameter before being distorted by wind and seismic magnitude of M4.8. (NASA; usgs.gov; IRIS – (2022).
<figure><img src="image_2.png" /></figure>

<figure><img src="image_3.png" /></figure>

**Fig. 1** – (A) The Site: Mosaic of the Observation Site between the Hunga Tonga-Huga Ha'apai volcano and the west coast of South America, wind trajectory modeling for possible dispersion and deposition of ash at tropospheric altitude between days 15 December 2021 to January 18, 2022. Courtesy: HYSPLIT – NASA, (2022). (B) Ionogram of January 15, 2022 at 02:03:04 UTC, in Jicamarca (Peru), using the VIPIR technique. Courtesy: LISN/IGP, (2022).

Ionsonde – VIPIR (Vertical Incidence Pulsed Ionospheric Radar)

VIPIR is a fully digital frequency radar that operates between 0.3 and 26 MHz. It has 8 digital receivers and a digital transmission exciter. It has extremely high-performance analog receiving electronics and a 4 kW solid-state amplifier provide an interface to the real world. This work shows an application of ionograms recorded by this Ionosonde (Fig. 2). Due to the Earth's magnetic field, the ionosphere is birefringent at radio frequencies - there are two possible propagation modes, called ordinary (O) and extraordinary (X) mode. This means that there is a high frequency (HF) radio band sweep, normally they find two distinct ionospheric returns for each frequency. For automatic scaling of ionograms, it is highly desirable to be able to separate the two modes (HARRIS and PEDERICK, 2017).

The acquisition of the ionograms was carried out by the Low-Latitude Ionospheric Sensor Network – Instituto Geofisico del Perú - IGP, at the Jicamarca Radio Observatory (JRO) JM91J, (Lima - Peru), as it has a VIPIR acquisition technique system (Fig. 2), and be ideal for viewing the Magnetic Equator proximity anomaly.

<figure><img src="image_4.png" /></figure>

**Fig. 2** - Equipment set (Double-sided): Model – VIPIR: Vertical Incidence Pulsed Ionospheric Radar Very high interference immunity: IP3 > 45 dBm; High Dynamic Range: 115(I) +30(V) dB; Direct RF sampling 14 bits at 80 MHz; Fully digital conversion, receiver and exciter; Waveform Agility: 2 µs to 2 ms pulse/chip width; USB-2 Data and Command/Control Interfaces; 8 coherent receive channels; Frequency: 0.3 – 26 MHz; 4 kW class AB pulse amplifier; 3rd harmonic < -30 dBc; Precise GPS timing possible for bi-static operation; Radar software Open Source C code; runs under Linux. Courtesy: National Oceanic and Atmospheric Administration – NOAA and National Geophysical Data Center | Terence.Bullet@colorado.edu (2018).
<figure><img src="image_5.png" /><figcaption>**Fig. 3** - Panel of Ionograms of the times (00 UTC; 01 UTC; 02 UTC and 03 UTC) in Jicamarca for January 15, 2022. Courtesy: LISN | IGP, 2022.</figcaption></figure>

## Results and Discussion

In order to understand the results of the ionograms and modeling, we will have to start our observations with the records of Geoscience research agencies (NASA, NOAA, INVG, USGS) that justifies the phenomenon recorded on the volcanic eruption event that occurred in the Central Pacific near the island of Tonga on January 15, 2022.

Comparing the energy of the volcanic explosion with that released by another type of explosion, such as the Hiroshima bomb (Mw = 4.8), the magnitude Mw = 5.7 calculated for the Tonga eruption corresponds to a load of 355,000 tons of TNT (equivalent to TNT), therefore, at least 25 times larger than the Hiroshima explosion (equivalent to 15,000 tons of TNT), (INVG, 2022). For this observation, Ionosonda Digital - VIPIR in Jicamarca records the day of January 15, 2022, (Fig. 3), in the first four ionograms of a total of 24 ionograms in the 1 h time sequence between them, for this work.

The event in the Central Pacific began at 17 UTC. At this time on the west coast of South America (Jicamarca - Peru) it was 01 UTC, (Peru is -5 UTC).

In Fig. 3, at the time of (00:03:04 UTC) it is 19 HL and the Pre-Reverse Peak is taking place in the Electric Field, that is, the inversion of the direction of the Terrestrial Electric Field is taking place, whose effect is a strong elevation altitude of the F layer, at this moment the ionogram registers strong echoes over the F layer, that is, defined close to 300 km of altitude. At, (01:03:04 UTC) there is an echo decrease over the VIPIR signal (transmission) with more definition of the F layer at 350 km altitude. At, (02:03:04 UTC) there is an appearance of Spread-F (Plasma Bubbles) in the signal with altitude 420 km altitude. In, (03:03:04 UTC) F layer wrapped in full Spread-F (Plasma Bubble) at 480 km altitude.
<figure><img src="image_6.png" /><figcaption>**Fig. 4** - Ionogram Panel of the times (04 UTC; 05 UTC; 06 UTC and 07 UTC) in Jicamarca for January 15, 2022. Courtesy: LISN | IGP, 2022.</figcaption></figure>

In Fig. 4, we have at (04:03:04 UTC) a fully diffused signal in Spread-F, close to 400 km of altitude. In, (05:03:04 UTC) Plasma bubbles involved in the F layer with strong echo in the Radar signal - VIPIR. At, (06:03:04 UTC) very strong echoes for all sweep frequencies of the Ionsonde Plasma Bubble formation. (07:03:04) decreases the Plasma Bubbles and the ordinary and extraordinary signals now appear to be more defined for F1 and F2 and signal reflection for F2 with ionospheric plasma scattering.

For Fig. 5, from (08:03:04 UTC) the Radar signal (VIPIR) tends to disappear, remaining thus at (09:03:04 UTC) and (10:03:04 UTC), returning slowly appearing at (11:03:04 UTC), but for the low frequencies of Ionsonde at 300 km altitude. This effect on the ionograms is strongly linked to Gravity Waves (GW) brought to the Ionosphere by tropospheric winds from the eruption of the Hunga Tonga-Hunga Ha'apai volcano at 08 UTC, in the Central Pacific.

At, Fig. 6, (12:03:04 UTC), the GW remain in the high atmosphere environment scattering the ionospheric plasma and begin to appear at an altitude of 100 km approximately in the form of a sporadic E layer, with the radar signal producing strong echoes and the definition of the heights of layers F1 and F2 confused at this time. For the times of (13:03:04 UTC), (14:03:04 UTC) and (15:03:04 UTC) in the range of 4 h to 6 h from the beginning of the volcano eruption, a strong connection is noted of the reflected signal from the plasma between 100 km to 600 km with definition of F1 and F2 and the acquisition signals of O and X, well defined. It is known that when the ionosphere has regions with very rarefied plasma density, the acquisitions (O and X) are more difficult to define the heights of the F1 and F2 layers.

In Fig. 7, at (16:03:04 UTC), (17:03:04 UTC), (18:03:04 UTC) and (19:03:04 UTC) we observe the influence of GW on the ionospheric plasma, with Es formation for all Ionsonde scanning frequencies and F3 layer formation after 17 UTC.
<figure><img src="image_7.png" /><figcaption>Fig. 4 - Ionogram Panel of the times (04 UTC; 05 UTC; 06 UTC and 07 UTC) in Jicamarca for January 15, 2022. Courtesy: LISN | IGP, 2022.</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>Fig. 5 – Timetable Ionogram Panel (08 UTC; 09 UTC; 10 UTC and 11 UTC) in Jicamarca for January 15, 2022. Courtesy: LISN | IGP, 2022.</figcaption></figure>
<figure><img src="image_9.png" /><figcaption>**Fig. 6** - Timetable Ionogram Panel (12 UTC; 13 UTC; 14 UTC and 15 UTC) in Jicamarca for January 15, 2022. Courtesy: LISN | IGP, 2022.</figcaption></figure>

<figure><img src="image_10.png" /><figcaption>**Fig. 7** - Timetable Ionogram Panel (16 UTC; 17 UTC; 18 UTC and 19 UTC) in Jicamarca for January 15, 2022. Courtesy: LISN | IGP, 2022.</figcaption></figure>
<figure><img src="image_11.png" /><figcaption>**Fig. 8** - Timetable Ionogram Panel (20 UTC; 21 UTC; 22 UTC and 23 UTC) in Jicamarca for January 15, 2022. Courtesy: LISN | IGP, 2022.</figcaption></figure>

The modeling of the dispersion and deposition of volcanic ash shows the global dimension of the phenomenon. Comparing the energy of the volcanic explosion with that released by another type of explosion, such as the Hiroshima bomb (Mw = 4.8), the magnitude Mw = 5.7 calculated for the Tonga eruption corresponds to a load of 355,000 tons of TNT (equivalent to TNT), therefore at least 25 times greater than the Hiroshima explosion (equivalent to 15,000 tons of TNT) and P and S seismic waves, traveling at speeds between > 340 m/s (in air) at 1450 m/s (in water). (INGV, 2022). The consequence of the shock wave at the ocean-atmosphere interface is devastating and produces a large difference in pressure, rumble and ejection of particulate matter that are projected in the first moment at an altitude greater than 15 km (NASA Earth Observatory System, 2022).

Fig. 9 shows the modeling in the volcano scenario and the ash dispersion to 15 km of altitude in the first 12 h of the event, if we compare the aerial of the spot, with the city of São Paulo in Brazil, which is 1,521 km2, the largest city in South America, the spot is more than 36 times bigger, even in the first 12 hours.

## Conclusion

Observations in the Equatorial Ionosphere using Digital Ionosonde - VIPIR in Jicamarca (-11.9523954; -76.8757172) and HYSPLIT Modeling of trajectory and ash dispersion, showed efficient and strong accuracy. They also showed the propagation of Gravity Waves, shortly after the eruption of the Hunga Tonga-Hunga Ha'apai volcano (17 HL Tonga, 08 HL London and 03 HL Jicamarca).

This work begins by announcing a series of 24 Ionograms with a 1 h interval, which described the behavior of the Equatorial Ionosphere very close to (or over) the Magnetic Equator on the west coast of South America. Confirming the point location anomaly (-11.9523954; -76.8757172), by enabling the visualization by Ionograms at the time of (00:03:04 UTC to 07:03:04 UTC) the development of Ionospheric Plasma Bubbles throughout the dawn of January 15, 2022. It also identifies the propagation of Gravity Waves in the equatorial position during (08:03:04 UTC and 10:03:04 UTC) the visual identification by Ionograms, through the disappearance or removal (profile of the F layer) in the target of the echoes that should return to the Radar Digital, ie the scanning of the VIPIR
<figure><img src="image_12.png" /><figcaption>**Fig. 9** – Modeling of the dispersion and deposition of ash from the Hunga Tonga-Huga Ha'apai volcano (-20.8229; -175.4376) for the first 12 h of the beginning of the event, at an altitude of 15 km.
Courtesy: HYSPLIT – Vulcan Ash. (NASA).</figcaption></figure>

frequency range (0.3 – 26 MHz) was compromised by GW. The profiles very slowly return to appear on the VIPIR screen at (11:03:04 UTC). Tropospheric winds of > 340 m/s in the atmosphere (NASA, USGS, INGV) (with a certain inclination, shear with stratospheric winds, also with a certain inclination within the atmospheric envelope of the Earth Magnetic Field, inducing an altitude of approximately 100 km (on Screen of VIPIR) the formation of a Sporadic layer – Es. A fact already discussed by Hines, 1964, confirming Lorentz's theory for particles or charges immersed with great speed in a magnetic field, the effect of rotation and displacement. volcano expels particulate material rich in metallic ions (HERRMANN, et al., 1978), which rise and favor the construction of Es throughout 15 January 2022. Also, during the daytime phase (18:03:04 UTC – 14 HL), formation of a third layer F (F3) appears and remains until (20:03:04 UTC). of the Hunga Tonga-Hunga Ha'apai, in the range of (07:03:04 UTC to 23:03:04). During the day phase, the acquisition of information by the O/X signal (ordinary and extraordinary) are well defined in the ionograms, since, during the night, the Spread-F formation is constant, confusing the visualization of a given signal.

The trajectory HYSPLIT Modeling (Fig. 1-A) and ash dispersion (Fig. 9) confirm the efficiency and accuracy of the VIPIR in Jicamarca.

The authors, however, indicate that more information can be extracted with these two instruments used in this observation.
Acknowledgments

The authors are immensely grateful for the
courtesy of Low-Latitude Ionospheric Sensor
Network – LISN, Instituto Geofisico del Perú – IGP
and the Ministry of the Environment of Peru, for
making the information available by Ionograms
(VIPIR | O/X) from Station JM91J: Jicamarca
Radio Observatory – JRO. We also thank the Air
Resources Laboratory (NOAA-NASA) for making
available the HYSPLIT - models that simulate the
dispersion and trajectory of substances
transported and dispersed through our
atmosphere, on local to global scales. We thank
the support of the researchers' institution:
CEULM/ULBRA – SEDUC-AM – CIESA – FMF-
Wyden, Dr. Evandro Barbosa Brandão
(CEULM/ULBRA-Manaus-Brasil) to Dr. Troy
Beldini (UFOPA-Santarém-Brazil), the agencies
NASA, NOAA, INGV, USGS for relevant
information about the research object of the
article.

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