A global scale picture of ionospheric peak electron density changes during geomagnetic storms

Abstract

Changes in ionospheric plasma densities can affect society more than ever because of our increasing reliance on communication, surveillance, navigation, and timing technology. Models struggle to predict changes in ionospheric densities at nearly all temporal and spatial scales, especially during geomagnetic storms. Here we combine a 50 year (1965–2015) geomagnetic disturbance storm time (Dst) index with plasma density measurements from a worldwide network of ~132 vertical incidence ionosondes to develop a picture of global scale changes in peak plasma density due to geomagnetic storms. Vertical incidence ionosondes provide measurements of the critical frequency of the ionospheric F2 layer (foF2), a direct measure of the peak electron density (NmF2) of the ionosphere. By dissecting the NmF2 perturbations with respect to the local time at storm onset, season, and storm intensity, it is found that (i) the storm‐associated depletions (negative storm effects) and enhancements (positive storm effects) are driven by different but related physical mechanisms, and (ii) the depletion mechanism tends to dominate over the enhancement mechanism. The negative storm effects, which are detrimental to HF radio links, are found to start immediately after geomagnetic storm onset in the nightside high‐latitude ionosphere. The depletions in the dayside high‐latitude ionosphere are delayed by a few hours. The equatorward expansion of negative storm effects is found to be regulated by storm intensity (farthest equatorward and deepest during intense storms), season (largest in summer), and time of day (generally deeper on the nightside). In contrast, positive storm effects typically occur on the dayside midlatitude and low‐latitude ionospheric regions when the storms are in the main phase, regardless of the season. Closer to the magnetic equator, moderate density enhancements last up to 40 h during the recovery phase of equinox storms, regardless of the local time. Strikingly, high‐latitude plasma densities are moderately enhanced for up to 60 h prior to the actual onset of storms during the equinoxes and summer; a potential precursor of a geomagnetic storm.

Ionospheric Response to the St. Patrick's Day Space Weather Events in March 2012, 2013, and 2015 at Southern Low and Middle Latitudes

“…The hourly values of f o F 2 measured with the ionosonde at two low‐latitude stations, DW (geomagnetic coordinates, 21.96°S, 202.84°E) and Townsville (TV; 28.95°S, 220.72°E), and three midlatitude stations, BR (36.73°S, 228.93 ο E), CB (45.65°S, 226.30°E), and Hobart (HO; 54.17°S, 226.52°E), were obtained from the World Data Centre, Bureau of Meteorology, Australia (online at http://www.sws.bom.gov.au/World_Data_Centre). The f o F 2 values are scaled to the nearest 0.1 MHz (Kumar & Parkinson, ). The local time of stations is given as follows: LT (DW) = UT + 8.7 hr, LT (TV) = UT + 9.8 hr, LT (BR) = UT + 10.2 hr, LT (CB) = UT + 9.9 hr, and LT (HO) = UT + 9.8 hr.…”

“…The values of f o F 2 extracted online are scaled up by a factor of 10, and the same values have been used in our analysis. The f o F 2 is also used to calculate N m F 2 of the F 2 region ionosphere using a simple relationship, , where f o F 2 is in megahertz (Kumar & Parkinson, ). The stations within geomagnetic latitude 10–30°S are considered as low‐latitude stations and stations within 30–60°S as midlatitude stations.…”

“…The (Kumar & Parkinson, 2017). The local time of stations is given as follows: LT (DW) = UT + 8.7 hr, LT (TV) = UT + 9.8 hr, LT (BR) = UT + 10.2 hr, LT (CB) = UT + 9.9 hr, and LT (HO) = UT + 9.8 hr.…”

“…The storm‐time increase/decrease in f o F 2 /TEC is referred to as a positive/negative ionospheric storm (Astafyeva et al, ; Kumar, , Mendillo, ; Titheridge & Buonsanto, ). Kumar and Parkinson () using 50 years (1965–2015) of geomagnetic disturbance and f o F 2 data from a worldwide network of 132 vertical incidence ionosondes have analyzed a global picture of ionospheric storms in N m F 2 . The high‐latitude Joule heating (JH), which could persist for several days, is associated with auroral electric currents and generates storm‐time thermospheric neutral winds with decreased O/N 2 density ratio and gravity waves, which can generate traveling atmospheric disturbances (TADs)/traveling ionospheric disturbances (TIDs; e.g., Balan et al, ; Habarulema et al, ).…”

Temperature and pressure variability in mid-latitude low atmosphere and stratosphere-ionosphere coupling

“…Understanding of variations of ionospheric parameters is not only scientifically important but also necessary from the practical and technological points of view. Variations in ionospheric plasma densities change conditions for the radio signal propagation and, consequently, affect the functioning of the satellite based communication, surveillance, and navigation systems (e.g., Kumar and Parkinson, 2017). In this paper we focus on the variations of the ionospheric conditions above the Iberian Peninsula middle latitudinal region.The ionosphere shows coupling both with the underlying neutral atmosphere and the overlying magnetosphere (Chapman and Bartels, 1951;Kazimirovsky and Kokourov, 1991).…”