Bibliography

The 15 January 2022 Hunga Tonga Eruption History as Inferred From Ionospheric Observations

On 15 January 2022, the Hunga Tonga-Hunga Ha’apai submarine volcano erupted violently and triggered a giant atmospheric shock wave and tsunami. The exact mechanism of this extraordinary eruptive event, its size and magnitude are not well understood yet. In this work, we analyze data from the nearest ground-based receivers of Global Navigation Satellite System to explore the ionospheric total electron content (TEC) response to this event. We show that the ionospheric response consists of a giant TEC increase followed by a strong long-lasting depletion. We observe that the explosive event of 15 January 2022 began at 04:05:54UT and consisted of at least five explosions. Based on the ionospheric TEC data, we estimate the energy released during the main major explosion to be between 9 and 37 Megatons in trinitrotoluene equivalent. This is the first detailed analysis of the eruption sequence scenario and the timeline from ionospheric TEC observations.

Astafyeva, E.; Maletckii, B.; Mikesell, T.; Munaibari, E.; Ravanelli, M.; Coisson, P.; Manta, F.; Rolland, L.;

Published by: Geophysical Research Letters      Published on:

YEAR: 2022     DOI: 10.1029/2022GL098827

co-volcanic ionospheric disturbances; eruption timeline; GNSS; Hunga Tonga eruption; Ionosphere; ionospheric geodesy

Ionospheric Disturbances and Irregularities during the 25--26 August 2018 Geomagnetic Storm

We use ground-based (GNSS, SuperDARN, and ionosondes) and space-borne (Swarm, CSES, and DMSP) instruments to study ionospheric disturbances due to the 25–26 August 2018 geomagnetic storm. The strongest large-scale storm-time enhancements were detected over the Asian and Pacific regions during the main and early recovery phases of the storm. In the American sector, there occurred the most complex effects caused by the action of multiple drivers. At the beginning of the storm, a large positive disturbance occurred over North America at low and high latitudes, driven by the storm-time reinforcement of the equatorial ionization anomaly (at low latitudes) and by particle precipitation (at high latitudes). During local nighttime hours, we observed numerous medium-scale positive and negative ionospheric disturbances at middle and high latitudes that were attributed to a storm-enhanced density (SED)-plume, mid-latitude ionospheric trough, and particle precipitation in the auroral zone. In South America, total electron content (TEC) maps clearly showed the presence of the equatorial plasma bubbles, that, however, were not seen in data of Rate-of-TEC-change index (ROTI). Global ROTI maps revealed intensive small-scale irregularities at high latitudes in both hemispheres within the auroral region. In general, the ROTI disturbance “imaged” quite well the auroral oval boundaries. The most intensive ionospheric fluctuations were observed at low and mid-latitudes over the Pacific Ocean. The storm also affected the positioning accuracy by GPS receivers: during the main phase of the storm, the precise point positioning error exceeded 0.5 m, which is more than five times greater as compared to quiet days.

Astafyeva, E.; Yasyukevich, Y.; Maletckii, B.; Oinats, A.; Vesnin, A.; Yasyukevich, A.; Syrovatskii, S.; Guendouz, N.;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2022     DOI: 10.1029/2021JA029843

Geomagnetic storms; Ionosphere; ROTI; ionospheric disturbances; ionospheric irregularities; multi-instrumental approach

Unprecedented hemispheric asymmetries during a surprise ionospheric storm: A game of drivers

Astafyeva, Elvira; Bagiya, Mala; Förster, Matthias; Nishitani, Nozomu;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2020     DOI:

Game of drivers and a surprise ionospheric storm

For this purpose, we use a set of space-borne (the Swarm constellation, GUVI/TIMED) and ground-based (GPS receivers, magnetometers, SuperDARN) instruments. In the

Astafyeva, Elvira; Bagiya, Mala;

Published by:       Published on:

YEAR: 2019     DOI:

Study of the Equatorial and Low-Latitude Electrodynamic and Ionospheric Disturbances During the 22\textendash23 June 2015 Geomagnetic Storm Using Ground-Based and Spaceborne Techniques

We use a set of ground-based instruments (Global Positioning System receivers, ionosondes, magnetometers) along with data of multiple satellite missions (Swarm, C/NOFS, DMSP, GUVI) to analyze the equatorial and low-latitude electrodynamic and ionospheric disturbances caused by the geomagnetic storm of 22\textendash23 June 2015, which is the second largest storm in the current solar cycle. Our results show that at the beginning of the storm, the equatorial electrojet (EEJ) and the equatorial zonal electric fields were largely impacted by the prompt penetration electric fields (PPEF). The PPEF were first directed eastward and caused significant ionospheric uplift and positive ionospheric storm on the dayside, and downward drift on the nightside. Furthermore, about 45\ min after the storm commencement, the interplanetary magnetic field (IMF) Bz component turned northward, leading to the EEJ changing sign to westward, and to overall decrease of the vertical total electron content (VTEC) and electron density on the dayside. At the end of the main phase of the storm, and with the second long-term IMF Bz southward turn, we observed several oscillations of the EEJ, which led us to conclude that at this stage of the storm, the disturbance dynamo effect was already in effect, competing with the PPEF and reducing it. Our analysis showed no significant upward or downward plasma motion during this period of time; however, the electron density and the VTEC drastically increased on the dayside (over the Asian region). We show that this second positive storm was largely influenced by the disturbed thermospheric conditions.

Astafyeva, E.; Zakharenkova, I.; Hozumi, K.; Alken, P.; isson, Co; Hairston, M.; Coley, W.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 03/2018

YEAR: 2018     DOI: 10.1002/jgra.v123.310.1002/2017JA024981

Study of the equatorial and low-latitude electrodynamic and ionospheric disturbances during the 22—23 June 2015 geomagnetic storm using ground-based and spaceborne techniques

We use a set of ground-based instruments (Global Positioning System receivers, ionosondes, magnetometers) along with data of multiple satellite missions (Swarm, C/NOFS, DMSP, GUVI) to analyze the equatorial and low-latitude electrodynamic and ionospheric disturbances caused by the geomagnetic storm of 22–23 June 2015, which is the second largest storm in the current solar cycle.

Astafyeva, E; Zakharenkova, I; Hozumi, K; Alken, P; isson, Co; Hairston, Marc; Coley, William;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2018     DOI: 10.1002/2017JA024981

Study of the equatorial and low-latitude electrodynamic and ionospheric disturbances during the 22—23 June 2015 geomagnetic storm using ground-based and spaceborne techniques

Astafyeva, E; Zakharenkova, I; Hozumi, K; Alken, P; isson, Co; Hairston, Marc; Coley, William;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2018     DOI:

Prompt penetration electric fields and the extreme topside ionospheric response to the June 22--23, 2015 geomagnetic storm as seen by the Swarm constellation

Using data from the three Swarm satellites, we study the ionospheric response to the intense geomagnetic storm of June 22\textendash23, 2015. With the minimum SYM-H excursion of -207 nT, this storm is so far the second strongest geomagnetic storm in the current 24th solar cycle. A specific configuration of the Swarm satellites allowed investigation of the evolution of the storm-time ionospheric alterations on the day- and the nightside quasi-simultaneously. With the development of the main phase of the storm, a significant dayside increase of the vertical total electron content (VTEC) and electron density Ne was first observed at low latitudes on the dayside. From\ ~22\ UT of 22 June to\ ~1\ UT of 23 June, the dayside experienced a strong negative ionospheric storm, while on the nightside an extreme enhancement of the topside VTEC occurred at mid-latitudes of the northern hemisphere. Our analysis of the equatorial electrojet variations obtained from the magnetic Swarm data indicates that the storm-time penetration electric fields were, most likely, the main driver of the observed ionospheric effects at the initial phase of the storm and at the beginning of the main phase. The dayside ionosphere first responded to the occurrence of the strong eastward equatorial electric fields. Further, penetration of westward electric fields led to gradual but strong decrease of the plasma density on the dayside in the topside ionosphere. At this stage, the disturbance dynamo could have contributed as well. On the nightside, the observed extreme enhancement of the Ne and VTEC in the northern hemisphere (i.e., the summer hemisphere) in the topside ionosphere was most likely due to the combination of the prompt penetration electric fields, disturbance dynamo and the storm-time thermospheric circulation. From\ ~2.8\ UT, the ionospheric measurements from the three Swarm satellites detected the beginning of the second positive storm on the dayside, which was not clearly associated with electrojet variations. We find that this second storm might be provoked by other drivers, such as an increase in the thermospheric composition.

Astafyeva, Elvira; Zakharenkova, Irina; Alken, Patrick;

Published by: Earth, Planets and Space      Published on: 09/2016

YEAR: 2016     DOI: 10.1186/s40623-016-0526-x

Ionospheric response to the 2015 St. Patrick's Day storm: A global multi-instrumental overview

We present the first multi-instrumental results on the ionospheric response to the geomagnetic storm of 17\textendash18 March 2015 (the St. Patrick\textquoterights Day storm) that was up to now the strongest in the 24th solar cycle (minimum SYM-H value of -233 nT). The storm caused complex effects around the globe. The most dramatic positive ionospheric storm occurred at low latitudes in the morning (~100\textendash150\% enhancement) and postsunset (~80\textendash100\% enhancement) sectors. These significant vertical total electron content increases were observed in different local time sectors and at different universal time, but around the same area of the Eastern Pacific region, which indicates a regional impact of storm drivers. Our analysis revealed that this particular region was most concerned by the increase in the thermospheric O/N₂\ ratio. At midlatitudes, we observe inverse hemispheric asymmetries that occurred, despite the equinoctial period, in different longitudinal regions. In the European-African sector, positive storm signatures were observed in the Northern Hemisphere (NH), whereas in the American sector, a large positive storm occurred in the Southern Hemisphere, while the NH experienced a negative storm. The observed asymmetries can be partly explained by the thermospheric composition changes and partly by the hemispherically different nondipolar portions of the geomagnetic field as well as by the IMF By component variations. At high latitudes, negative ionospheric storm effects were recorded in all longitudinal regions, especially the NH of the Asian sector was concerned. The negative storm phase developed globally on 18 March at the beginning of the recovery phase.

Astafyeva, Elvira; Zakharenkova, Irina; Förster, Matthias;

Published by: Journal of Geophysical Research: Space Physics      Published on: 10/2015

YEAR: 2015     DOI: 10.1002/2015JA021629

geomagnetic storm; hemispheric asymmetry; Ionosphere; negative storm; positive storm; Swarm mission

Ionospheric and Thermospheric Response to the 2015 St. Patrick s Day Storm: a Global Multi-Instrumental Overview

We study the ionospheric response to the geomagnetic storm of 17-18 March 2015 (the St. Patrick s Day 2015 storm) that was up to now the strongest in the 24th solar cycle (minimum

Astafyeva, Elvira; Zakharenkova, Irina; Foerster, Matthias; Doornbos, Eelco; Encarnacao, Joao; Siemes, Christian;

Published by:       Published on:

YEAR: 2015     DOI: