Quasi-periodic ripples in high latitude electron content, the geomagnetic field, and the solar wind

Abstract

in this study we present evidence for the existence of quasi-periodic ripples in the f-region electron content at high latitude, the magnetic flux density at geosynchronous orbit, and the solar wind dynamic pressure and IMF flux density at L1. The ripples are shown to be continually present during all 14 days of observations in different years and seasons, and at all local times, though they are generally small in magnitude relative to the background. The frequencies of all the parameters are, on average, remarkably similar, and the amplitudes of the selected peaks of some parameters show strong correlations for which regression formulae are given. these results support the proposition that the ripples propagate from the solar wind to the f-region, and that they are a related, persistent phenomenon.Spatial and temporal structuring in the F-region of the ionosphere is a well-known phenomenon which has been observed on many occasions. The structures usually extend along the geomagnetic field and are, therefore, almost vertical at high latitudes.This paper is based on observations of quasi-periodic electron density structures in the high latitude F-region using the EISCAT Svalbard radar. A previous paper 1 , covering 24 hours of observations over 4 days in February and March 2015, showed the presence of F-region electron density structures with a median periodicity of about 22 minutes. The present investigation extends the scope of this study to include a further 10 days of electron density data in different years and seasons. Similar structures are reported in the geomagnetic field, and in the solar wind particle flux and IMF flux density. The relationship between these structures is investigated, and evidence for their origin is discussed.www.nature.com/scientificreports www.nature.com/scientificreports/ giving the electron content variations as a "ratio". (Refer to Validation of the smoothing procedure, comments regarding the efficacy of spectral analysis as an alternative approach, and the testing of this method using random data.) Using this smoothing procedure, Fig. 2 shows the variations in the electron content ratio derived for all four days over the height range 237.50 to 354.85 km; the variations appear to be quasi-periodic in nature. Peaks with magnitudes ≥1.03 were selected (see Selection criteria), and the 53 intervals between the 57 selected peaks are summarised in a histogram (Fig. 3). (Throughout this analysis, for any given set of data, there are occasional data gaps or intervals of bad data. Consequently, if n is the number of peaks sampled, the number of inter-peak periods can be less than n − 1). The median inter-peak period over all four days is 22 minutes, with quartiles at 18 and 26 minutes (Table 1a), and the daily medians are in the range 20-26 minutes. It is not obvious whether there was a dynamic component to the structures because these observations were made with a single, field-aligned radar beam. Scientific RepoRtS |(2020) 10:1313 | https://doi.

On Differentiating Multiple Types of ULF Magnetospheric Waves in Response to Solar Wind Periodic Density Structures

“…At nominal solar wind speeds, the PDSs correspond to structures with size scales of the order of the Earth's magnetosphere (Kepko et al., 2020 ). The resultant directly driven ULF waves, observed in the magnetosphere and at the ground, occur at similar frequencies falling within and extending beyond the Pc5 band (Birch & Hargreaves, 2020 ; Hartinger et al., 2014 ; Kepko et al., 2002 ; Kepko & Spence, 2003 ; Stephenson & Walker, 2002 ; Viall et al., 2009 ; Villante et al., 2016 ).…”

Evidence for presence of a global quasi-resonant mode of oscillations during high-intensity long-duration continuous AE activity (HILDCAA) events

“…The periodic changes in TEC over high latitude are expected due to the particle precipitation during geomagnetically disturbed conditions (Sato et al 2018;Chernyshov et al 2020). Recently, Birch and Hargreaves (2020) reported that the quasi-periodic oscillations of 25-27 min in the F-region electron content at high latitude, the magnetic field at geosynchronous orbit are caused by the solar wind pressure and IMF. Using the Coupled Magnetosphere-Ionosphere-Thermosphere Model (CITM), Liu et al (2018) and Zhang et al (2019) showed that the energy flow from the solar wind to MI-system strongly depends on the temporal changes in IMF Bz and it also controls the Joule heating, cross polar cap potential, auroral peak electron flux, the vertical plasma drift, and ionospheric F2 peak density variations globally.…”

Solar-Wind Structures That Are Not Destroyed by the Action of Solar-Wind Turbulence

“…These periodic solar-wind structures were first identified by examining the solar wind at Earth when spacecraft in the magnetosphere indicated that the magnetosphere was undergoing periodic compressions (Kepko et al, 2002); the solar-wind periodic structures are also responsible for periodic variations of the total electron content of the Earth's ionosphere (Birch and Hargreaves, 2020a). Periodic density oscillations are found typically in slow solar wind with periods in the range of 4-140 min, corresponding to radial wavelengths of 8 × 10 4 -3 × 10 6 km (Viall et al, 2008;Kepko et al, 2020), which are in the inertial range of scalesizes.…”