The Earth's ionosphere, a partly ionized plasma layer in the upper atmosphere extending from about 60 km to around 1000 km, is not only a playground for many fascinating phenomena such as the aurorae or plasma bubbles, but also affects many technological systems: Ionosphere and Ionospheric perturbations affect the propagation of electromagnetic waves (precision and reliability of GNSS, over the horizon radars, radio communications), ionospheric currents cause changes in the geomagnetic field, leading to geomagnetically induced currents that pose a risk to power line transformers.Ionospheric plasma is primarily generated by ionizing solar radiation. However, ionospheric dynamics and disturbances depend strongly on the interaction between the solar wind and the Earth's magnetosphere, which is tightly coupled to the ionosphere through field-aligned currents, electric fields, etc. In addition, the ionosphere is strongly linked to the neutral atmosphere, with which it partially merges and responds to processes that take place below in the neutral atmosphere. In particular, during geomagnetically quiet periods neutral atmosphere may account for 10-15% of the ionospheric variability. Atmospheric gravity waves, generated by a variety of processes in lower atmosphere, are the key vertical coupling agent, transferring energy and momentum into middle/upper atmosphere and ionosphere. Atmospheric thermal tides, both migrating and non-migrating, are responsible for diurnal, semidiurnal and terdiurnal variabilities.There are also reports of multi-day variabilities, matching the periods of various planetary waves, though the origin of these variabilities is still debated. Changes in global atmospheric circulations, e.g., seasonal or caused by sudden stratospheric warmings, can influence middle/upper atmosphere and ionosphere. A downward coupling to lower atmosphere, due to atmospheric gravity waves being generated by Joule heating in the ionospheric E-region, has been also proposed.Although the ionosphere has been studied for more than one hundred years, starting with the transatlantic transmission of radio signals, and the basic principles of ionospheric physics are well known, the instabilities and day-to-day variability needs to be further investigated because of the complex interactions 25 with the layers below and above it. The papers in this special issue attempt to describe and explain some of 26 these processes. The enhanced auroral energy deposition during HSSs is proposed as a mechanism for the generation of 31 downward propagating atmospheric gravity waves (AGWs). As AGWs reach lower atmosphere, they may 32 excite the conditional instability in the troposphere, thus leading to excessive precipitation. This downward 33 influence from solar wind to troposphere could be considered as a direct link between solar variability and 34 climate variability or trends.
Editorial16 January 2024
Editorial: Vertical coupling in the atmosphere-ionosphere-magnetosphere systemOPINION
10 October 2023
Dmytro Kotovand Oleksandr Bogomaz
2 Authors
- DK
Dmytro Kotov
Institute of Ionosphere, Ukraine
- OB
Oleksandr Bogomaz
Institute of Ionosphere, Ukraine
4,274 views
2 citations
CORRECTION
7 November 2023
Dmytro Kotovand Oleksandr Bogomaz
2 Authors
- DK
Dmytro Kotov
Institute of Ionosphere, Ukraine
- OB
Oleksandr Bogomaz
Institute of Ionosphere, Ukraine
1,081 views
ORIGINAL RESEARCH
29 September 2023
Ivana Molinaand Ludger Scherliess
3,360 views
3 citations
ORIGINAL RESEARCH
14 September 2023
Ivana Molinaand Ludger Scherliess
2,542 views
2 citations
ORIGINAL RESEARCH
31 July 2023
Paul Prikryland Vojto Rušin
A tendency of heavy-rainfall-induced floods in Canada to follow arrivals of solar wind high-speed streams (HSSs) from coronal holes is observed. Cool season precipitation events, including extreme freezing rain events in the province of New Brunswick, also tend to occur following HSSs. More direct evidence is provided using the satellite-based gridded precipitation data set IMERG in the superposed epoch analysis of high-rate precipitation. The results show an increase in the high-rate daily precipitation occurrence over Canada following arrivals of major HSSs. This is consistent with previously published results for other mid-latitude geographic regions. The ERA5 meteorological reanalysis is used to evaluate slantwise convective available potential energy (SCAPE) that is of importance in the development of storms. The role of the solar wind-magnetosphere-ionosphereatmosphere coupling, mediated by globally propagating aurorally excited atmospheric gravity waves releasing the conditional symmetric instability in the troposphere leading to convection and precipitation, is proposed. Extreme weather events, such as heavy precipitation leading to floods or flash floods particularly in summer, and snow-or ice-storms in winter, pose natural hazards with major socio-economic and environmental consequences (Brooks et al., 2001;Buttle et al. 2016). Despite advances made in forecasting and improved understanding of mesoscale processes (Doswell and Bosart 2001), predictions of extreme precipitation events continue to present difficult challenges (Doswell and Bosart 2001;Villarini et al. 2010;Gourley et al. 2012). Such events are common in Canada and with the climate change affecting the stability of Earth's atmosphere their occurrence is expected to increase (Burn and Whitfield 2016). Buttle et al. (2016; their Table 2) reviewed the key processes, classified as meteorological, hydrological, geomorphic and human induced, that generate floods in Canada.In this paper we focus on heavy precipitation events in Canada where the proximity of the auroral zone, the source region of atmospheric gravity waves (AGWs), makes it the most favorable geographic location to investigate the relationship between high-rate precipitation occurrence and solar wind high-speed streams.
Increased solar radiation during solar flare events can cause additional ionization and enhanced absorption of the electromagnetic (EM) waves in the ionosphere leading to partial or even total radio fade-outs. In this study, the ionospheric response to large solar flares has been investigated using the ionosonde data from Juliusruh (54.63° N, 13.37° E), Průhonice (49.98° N, 14.55° E) and San Vito (40.6° N, 17.8° E) Digisonde (DPS-4D) stations. We studied the effect of 13 intense (>C4.8) solar flares that occurred between 06:00 and 16:30 (UT, daytime LT=UT+1 h) from 04-10 September 2017 using three different methods. A novel method based on the amplitude data of the measured EM waves is used to calculate and investigate the relative absorption changes (compared to quiet period) occurring during the flares. The amplitude data are compared with the variation of the fmin parameter (fmin, the minimum measured frequency, it is considered as a qualitative proxy for the "nondeviative" radio wave absorption). Furthermore, the signal-to-noise ratio (SNR) measured by the Digisondes was used as well to quantify and characterize the fade-out events and the ionospheric absorption. In order to compare the three different methods, residuals have been defined for all parameters, which provide the percentage changes compared to the selected reference periods. Total and partial radio fade-outs, increased values (+0.4-318%) of the fmin parameter, and +20-1400% amplitude changes (measured at 2.5 and 4 MHz) were experienced during and after the investigated flares. Generally, the observed changes depended on the intensity, solar zenith angle and duration of the flare events. Although the three different methods have their own advantages/disadvantages and their limitations, the combination of them seems to be an efficient approach to monitor the ionospheric response to solar flares.
ORIGINAL RESEARCH
23 June 2023
Petra Koucká Knížová, 8 more and Jacek Kerum
10 Authors
- PK
Petra Koucká Knížová
Department of Ionosphere and Aeronomy, Czechia
- KP
Kateřina Potužníková
Department of Meteorology, Czechia
- KP
Kateřina Podolská
Department of Ionosphere and Aeronomy, Czechia
- PH
Patrick Hannawald
German Aerospace Center, Germany
- ZM
Zbyšek Mošna
Department of Ionosphere and Aeronomy, Czechia
- DK
Daniel Kouba
Department of Ionosphere and Aeronomy, Czechia
- JC
Jaroslav Chum
Department of Ionosphere and Aeronomy, Czechia
- SW
Sabine Wüst
German Aerospace Center, Germany
- MB
Michael Bittner
German Aerospace Center, Germany
- JK
Jacek Kerum
Department of Meteorology, Czechia
The ionosphere as a part of the Earth's atmosphere supports wide range oscillations. Within them acoustic-gravity waves (AGW) form an important part. AGWs distribute energy and momentum from the source region over large distances. Significant portion of AGWs originates in the lower atmosphere and propagates through the atmosphere up to the ionospheric heights where, due to the coupling between neutral and ionized particles, it could be detected as wave-like disturbances of the plasma. Primarily the ionosphere behavior is driven by solar and geomagnetic activity while the influence from neutral and below laying regions of the atmosphere most of the time forms substantially smaller part of the observed variability. However, it could significantly alter ionospheric behavior. Our study is limited to a time span of rather low solar and geomagnetic activity in order to highlight neutral atmosphere influence. In the study we focus on two tropospheric situations above Europe that may lead to AGW generation that propagate up to the F layer where they potentially induce variability that we observe within ionospheric plasma parameters.
A multi-instrumental analysis of the meridional ionospheric response is presented over Europe during the two largest ICME-driven geomagnetic storms of solar cycle #24 maximum. Data from 5 European digisonde stations, ground-based Global Navigation Satellite System, Total Electron Content (GNSS TEC), the ratio of the TEC difference (rTEC), as well as Swarm and Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite observations have been used for the investigation of selected intervals (11-17 November, 2012, and 16-25 March, 2015). The storm evolution is monitored by digisonde foF2 critical frequency (related to the maximum electron density of F2-layer) and GNSS TEC data. Moreover, Global Ultraviolet Imager (GUVI) measurements from the TIMED satellite are used to investigate the changes in the thermospheric O/N2 ratio. Our main focus was on the main phase of the geomagnetic storms, when during the nighttime hours extremely depleted plasma was detected. The extreme depletion is observed in foF2, TEC and rTEC, which is found to be directly connected to the equatorward motion of the midlatitude ionospheric trough (MIT) on the nightside. We demonstrate a method (beside the existing ones) which allows the monitoring of the storm-time evolution of the disturbances (e.g. MIT, SAPS, SED) in the thermosphere-ionosphere-plasmasphere system by the combined analysis of the worldwide digisonde system data (with the drift measurements and the ionospheric layer parameters with 5-15 minute cadence), with rTEC and GNSS TEC data, and with the satellite data like Swarm, TIMED/GUVI.
This paper presents a multi-instrument observational analysis of the equatorial plasma bubbles (EPBs) variation over the American sector during a geomagnetically quiet time period of 07--10 December 2019. The day-to-day variability of EPBs and their underlying drivers are investigated through coordinately utilizing the Global-scale Observations of Limb and Disk (GOLD) ultraviolet images, the Ionospheric Connection Explorer (ICON) in-situ and remote sensing data, the global navigation satellite system (GNSS) total electron content (TEC) observations, as well as ionosonde measurements. The main results are as follows: (1) The postsunset EPBs' intensity exhibited a large day-to-day variation in the same UT intervals, which was fairly noticeable in the evening of December 07, yet considerably suppressed on December 08 and 09, and then dramatically revived and enhanced on December 10. (2) The postsunset linear Rayleigh-Taylor instability growth rate exhibited a different variation pattern. It had a relatively modest peak value on December 07 and 08, yet a larger peak value on December 09 and 10. There was a two-hour time lag of the growth rate peak time in the evening of December 09 from other nights. This analysis did not show an exact one-to-one relationship between the peak growth rate and the observed EPBs intensity. (3) The EPBs' day-to-day variation has a better agreement with that of traveling ionospheric disturbances (TIDs) and atmospheric gravity waves (AGWs) signatures, which exhibited relatively strong wavelike perturbations preceding/accompanying the observed EPBs on December 07 and 10 yet relatively weak fluctuations on December 08 and 09. These coordinate observations indicate that the initial wavelike seeding perturbations associated with AGWs, together with the catalyzing factor of the instability growth rate, collectively played important roles to modulate the day-to-day variation of EPBs. A strong seeding perturbation could effectively compensate for a moderate strength of Rayleigh-Taylor instability growth rate and therefore their combined effect could facilitate EPB development. Lacking of proper seeding perturbations would make it a more inefficient process for the development of EPBs, especially with a delayed peak value of Rayleigh-Taylor instability growth rate.