Midlatitude postsunset plasma bubbles observed over Europe during intense storms in April 2000 and 2001

Plasma bubbles are prevalent features of the equatorial/low-latitude ionosphere which are seldom observed at middle and high latitudes. Understanding the influence of geomagnetic storms on plasma bubbles' migration to higher latitudes is an important space weather topic, since a geomagnetic storm is an important phenomenon of space weather. This paper reports on the first observations of postsunset/evening midlatitude plasma bubbles in the European sector during the main phase of severe storms (Dst=-200 nT) on 6 April 2000 and 11 April 2001. Plasma depletions observed in Global Navigation Satellite System total electron content measurements are confirmed with those observed from in situ Defense Meteorological Satellite Program ion density measurements. The results show that the plasma bubbles were migrating north at virtual speeds of 400 m/s and on each of the storm days they extended as far north as ~42° (geographic latitude). It is estimated that the plasma bubbles may have grown to a maximum apex height of approximately 4000 km. During the time of bubble occurrence, the evening midlatitude plasma was enhanced and the equatorial ionization anomaly extended to European midlatitudes. In addition, evidence of the upward plasma motion was found in ionosonde hmF2 and h'F measurements, while the interplanetary electric field Ey was enhanced. This was found to suggest that the possible mechanism for the enhancement of midlatitude plasma and subsequent midlatitude plasma bubbles occurrence was the eastward penetration electric field associated with Bz southward turning.Peer ReviewedPostprint (published version

Storm Time Global Observations of Largeâ Scale TIDs From Groundâ Based and In Situ Satellite Measurements

This paper discusses the ionosphere’s response to the largest storm of solar cycle 24 during 16â 18 March 2015. We have used the Global Navigation Satellite Systems (GNSS) total electron content data to study largeâ scale traveling ionospheric disturbances (TIDs) over the American, African, and Asian regions. Equatorward largeâ scale TIDs propagated and crossed the equator to the other side of the hemisphere especially over the American and Asian sectors. Poleward TIDs with velocities in the range â 400â 700 m/s have been observed during local daytime over the American and African sectors with origin from around the geomagnetic equator. Our investigation over the American sector shows that poleward TIDs may have been launched by increased Lorentz coupling as a result of penetrating electric field during the southward turning of the interplanetary magnetic field, Bz. We have observed increase in SWARM satellite electron density (Ne) at the same time when equatorward largeâ scale TIDs are visible over the Europeanâ African sector. The altitude Ne profiles from ionosonde observations show a possible link that stormâ induced TIDs may have influenced the plasma distribution in the topside ionosphere at SWARM satellite altitude.Key PointsIncreased SWARM in situ electron density toward high latitudes in presence of equatorward largeâ scale TIDsEvidence of equatorward TIDs in influencing altitudinal plasma distribution to the topside ionospherePossibility of poleward TIDs launched from the geomagnetic equatorial region with comparable velocity values in both hemispheresPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142539/1/jgra53978_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142539/2/jgra53978.pd

Multi-instrument observations of large-scale atmospheric gravity waves/traveling ionospheric disturbances associated with enhanced auroral activity over Svalbard

This study reports on observations of large-scale atmospheric gravity waves/traveling ionospheric disturbances (AGWs/TIDs) using Global Positioning System (GPS) total electron content (TEC) and Fabry–Perot Interferometer’s (FPI’s) intensity of oxygen red line emission at 630 nm measurements over Svalbard on the night of 6 January 2014. TEC large-scale TIDs have primary periods ranging between 29 and 65 min and propagate at a mean horizontal velocity of ~749–761 m/s with azimuth of ~345–347° (which corresponds to poleward propagation direction). On the other hand, FPI large-scale AGWs have larger periods of ~42–142 min. These large-scale AGWs/TIDs were linked to enhanced auroral activity identified from co-located all-sky camera and IMAGE magnetometers. Similar periods, speed and poleward propagation were found for the all-sky camera (~60–97 min and ~823 m/s) and the IMAGE magnetometers (~32–53 min and ~708 m/s) observations. Joule heating or/and particle precipitation as a result of auroral energy injection were identified as likely generation mechanisms for these disturbances. © 2018 COSPAR. Published by Elsevier Ltd. All rights reserved

Multi-instrument observations of large-scale atmospheric gravity waves/traveling ionospheric disturbances associated with enhanced auroral activity over Svalbard

This study reports on observations of large-scale atmospheric gravity waves/traveling ionospheric disturbances (AGWs/TIDs) using Global Positioning System (GPS) total electron content (TEC) and Fabry-Perot Interferometer’s (FPI’s) intensity of oxygen red line emission at 630 nm measurements over Svalbard on the night of 6 January 2014. TEC large-scale TIDs have primary periods ranging between 29 and 65 minutes and propagate at a mean horizontal velocity of ∼749–761 m/s with azimuth of ∼345°–347° (which corresponds to poleward propagation direction). On the other hand, FPI large-scale AGWs have larger periods of ∼42–142 minutes. These large-scale AGWs/TIDs were linked to enhanced auroral activity identified from co-located all-sky camera and IMAGE magnetometers. Similar periods, speed and poleward propagation were found for the all-sky camera (∼60–97 minutes and ∼823 m/s) and the IMAGE magnetometers (∼32–53 minutes and ∼708 m/s) observations. Joule heating or/and particle precipitation as a result of auroral energy injection were identified as likely generation mechanisms for these disturbances

Counter-Electrojet Occurrence as Observed From C/NOFS Satellite and Ground-Based Magnetometer Data Over the African and American Sectors

An analysis of the counter-electrojet occurrence (CEJ) during 2008-2014 is presented for the African and American sectors based on local daytime (0700-1700 LT) observations from the Communications and Navigation Outage Forecasting System (C/NOFS) vertical ion plasma drift (equivalent to vertical Eà B at an altitude of about 400 km) and ground-based magnetometers. Using quiet time (Kp- 3) data, differences and/or similarities between the two data sets with reference to local time and seasonal dependence are established. For the first time, it is shown that C/NOFS satellite data are consistent with magnetometer observations in identifying CEJ occurrences during all seasons. However, C/NOFS satellite data show higher CEJ occurrence rate for almost all seasons. With respect to local time, C/NOFS satellite observes more CEJ events than magnetometer observations by average of about 20% and 40% over the American and African sectors, respectively, despite both data sets showing similar trends in CEJ identification. Therefore, when a space weather event occurs, it is important to first establish the original variability nature and/or magnitude of the eastward electric field in equatorial regions before attributing the resulting changes to solar wind-magnetosphere and ionosphere coupling processes since CEJ events can be present even during quiet conditions.Key PointsA statistical trend of CEJ events using C/NOFS satellite vertical ion plasma drift and magnetometer observations has been establishedBoth C/NOFS satellite and magnetometer data show higher CEJ occurrence rate over the African sector than the American sectorC/NOFS satellite data exhibit more CEJ events than magnetometer data by average of 20% (40%) over the American (African) sectorPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151259/1/swe20897.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151259/2/swe20897_am.pd

Midlatitude postsunset plasma bubbles observed over Europe during intense storms in April 2000 and 2001

Plasma bubbles are prevalent features of the equatorial/low-latitude ionosphere which are seldom observed at middle and high latitudes. Understanding the influence of geomagnetic storms on plasma bubbles' migration to higher latitudes is an important space weather topic, since a geomagnetic storm is an important phenomenon of space weather. This paper reports on the first observations of postsunset/evening midlatitude plasma bubbles in the European sector during the main phase of severe storms (Dst=-200 nT) on 6 April 2000 and 11 April 2001. Plasma depletions observed in Global Navigation Satellite System total electron content measurements are confirmed with those observed from in situ Defense Meteorological Satellite Program ion density measurements. The results show that the plasma bubbles were migrating north at virtual speeds of 400 m/s and on each of the storm days they extended as far north as ~42° (geographic latitude). It is estimated that the plasma bubbles may have grown to a maximum apex height of approximately 4000 km. During the time of bubble occurrence, the evening midlatitude plasma was enhanced and the equatorial ionization anomaly extended to European midlatitudes. In addition, evidence of the upward plasma motion was found in ionosonde hmF2 and h'F measurements, while the interplanetary electric field Ey was enhanced. This was found to suggest that the possible mechanism for the enhancement of midlatitude plasma and subsequent midlatitude plasma bubbles occurrence was the eastward penetration electric field associated with Bz southward turning.Peer Reviewe

A Statistical Study of Poleward Traveling Ionospheric Disturbances Over the African and American Sectors During Geomagnetic Storms

We present statistical results of traveling ionospheric disturbances (TIDs) with origin near the geomagnetic equator during geomagnetic storms that occurred within the period of 2010–2018. Based on storm criteria of Kp > 4 and Dst ≤ −50 nT, we have analyzed total electron content perturbations derived from Global Navigational Satellite Systems observations within a latitude range of 40°S–60°N and longitude ranges of 20°–40°E and 50°–70°W representing the African and American sectors. Although the northern hemispheric part of the African sector has limited data coverage, results show that the launched TIDs do not exceed the latitudinal distance of 20°–25° from their origin during the analyzed period. A statistically similar result is observed over the American sector with launched poleward TIDs constrained largely within ±20°–30° around the geomagnetic equator. Where data are available, majority of these cases are linked to changes in ionospheric electrodynamics, especially the enhancement of equatorial electrojet (EEJ), although there are other observations that are not explained by EEJ variability. This indicates that there may be other physical mechanisms that play a role in launching TIDs at the geomagnetic equator during disturbed conditions. An important result is that large‐scale and medium‐scale TIDs have been found to occur predominantly during the main and recovery phases of geomagnetic storms, respectively, at least over the African sector.Key PointsStorm‐time‐related poleward traveling ionospheric disturbances (TIDs) originating from the geomagnetic equatorial region occur mainly during local daytimeLarge scale poleward TIDs are observed during the main phase while medium‐scale TIDs dominate the recovery phase, at least over the African sectorIncreased vertical E × B drift plays a crucial role in launching poleward TIDsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/172076/1/jgra57097_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/172076/2/jgra57097.pd

Thermospheric Neutral Wind Measurements and Investigations across the African Region—A Review

This paper briefly reviews studies of thermospheric neutral wind dynamics over the African region. The literature includes a review of the observations of neutral winds over five African locations using the Fabry–Perot Interferometer (FPI), and the comparison between the FPI observations and predictions of the horizontal wind model (HWM-14). So far, there are reports of FPI thermospheric wind measurements in South Africa and Morocco representing the mid-latitude regions in the southern and northern hemispheres, respectively. Within the low latitudes, FPI instruments are installed in the Ivory Coast, Ethiopia, and Nigeria. For the literature reviewed, the years covered in the FPI data are 2018–2019 (South Africa), 2016–2017 (Nigeria), 2015–2016 (Ethiopia), 2013–2016 (Morocco), and 1994–1995 (Ivory Coast). Overall, the HWM-14 reproduces the climatological behavior of the meridional and zonal winds, with varying levels of fidelity for the different regions. The HWM-14 is more accurate in the stations located in the northern hemisphere of the African region; a result attributed to the presence of data during the development of this empirical model

Atmospheric and ionospheric waves induced by the Hunga eruption on 15 January 2022; Doppler sounding and infrasound

The massive explosive eruption of the Hunga volcano on 15 January 2022 generated atmospheric waves that were recorded around the globe and affected the ionosphere. The paper focuses on observations of atmospheric waves in the troposphere and ionosphere in Europe, however, a comparison with observations in East Asia, South Africa and South America is also provided. Unlike most recent studies of waves in the ionosphere based on the detection of changes in the total electron content, this study builds on detection of ionospheric motions at specific altitudes using continuous Doppler sounding. In addition, much attention is paid to long-period infrasound (periods longer than ∼50 s), which in Europe is observed simultaneously in the troposphere and ionosphere about an hour after the arrival of the first horizontally propagating pressure pulse (Lamb wave). It is shown that the long-period infrasound propagated approximately along the shorter great circle path, similar to the previously detected pressure pulse in the troposphere. It is suggested that the infrasound propagated in the ionosphere probably due to imperfect refraction in the lower thermosphere. The observation of infrasound in the ionosphere at such large distances from the source (over 16 000 km) is rare and differs from ionospheric infrasound detected at large distances from the epicenters of strong earthquakes, because in the latter case the infrasound is generated locally by seismic waves. An unusually large traveling ionospheric disturbance (TID) observed in Europe and associated with the pressure pulse from the Hunga eruption is also discussed. Doppler sounders in East Asia, South Africa and South America did not record such a significant TID. However, TIDs were observed in East Asia around times when Lamb waves passed the magnetically conjugate points. A probable observation of wave in the mesopause region in Europe approximately 25 min after the arrival of pressure pulse in the troposphere using a 23.4 kHz signal from a transmitter 557 km away and a coincident pulse in electric field data are also discussed.Fil: Chum, Jaroslav. Czech Academy of Sciences; República ChecaFil: Idelářová, Tereza. Czech Academy of Sciences; República ChecaFil: Kníová, Petra Koucká. Czech Academy of Sciences; República ChecaFil: Podolská, Kateřina. Czech Academy of Sciences; República ChecaFil: Rusz, Jan. Czech Academy of Sciences; República ChecaFil: Base, Jiří. Czech Academy of Sciences; República ChecaFil: Nakata, Hiroyuki. Chiba University; JapónFil: Hosokawa, Keisuke. University Of Electrocommunications; JapónFil: Danielides, Michael. Danielides Space Science Consulting; AlemaniaFil: Carsten, Schmidt. German Aerospace Center.; AlemaniaFil: Knez, Leon. German Aerospace Center.; AlemaniaFil: Liu, Jann Yenq. National Central University; ChinaFil: Molina, Maria Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología; ArgentinaFil: Fagre, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología; ArgentinaFil: Katamzi Joseph, Zama. South African National Space Agency; SudáfricaFil: Ohya, Hiroyo. Chiba University; JapónFil: Omori, Tatsuya. Chiba University; JapónFil: Lastovicka, Jan. Czech Academy of Sciences; República ChecaFil: Obrazova Buresova, Dalia. Czech Academy of Sciences; República ChecaFil: Kouba, Daniel. Czech Academy of Sciences; República ChecaFil: Urbar, Jaroslav. Czech Academy of Sciences; República ChecaFil: Truhlık, Vladimır. Czech Academy of Sciences; República Chec