Ionospheric Pc1 waves during a storm recovery phase observed by the China Seismo-Electromagnetic Satellite

Abstract

Abstract. During the storm recovery phase on 27 August 2018, the China Seismo-Electromagnetic Satellite (CSES) detected Pc1 wave activities in both the Northern Hemisphere and Southern Hemisphere in the high-latitude, post-midnight ionosphere with a central frequency of about 2 Hz. Meanwhile, the typical Pc1 waves were simultaneously observed for several hours by the Sodankylä Geophysical Observatory (SGO) stations on the ground. In this paper, we study the propagation characteristics and possible source regions of those waves. Firstly, we find that the Pc1 waves observed by the satellites exhibited mixed polarisation, and the wave normal is almost parallel with the background magnetic field. The field-aligned Poynting fluxes point downwards in both hemispheres, implying that the satellites are close to the wave injection regions in the ionosphere at about L=3. Furthermore, we also find that the estimated position of the plasmapause calculated by models is almost at L=3. Therefore, we suggest that the possible sources of waves are near the plasmapause, which is consistent with previous studies in that the outward expansion of the plasmasphere into the ring current during the recovery phase of geomagnetic storms may generate electromagnetic ion cyclotron (EMIC) waves, and these EMIC waves propagate northwards and southwards along the background magnetic field to the ionosphere at about L=3. Additionally, the ground station data show that Pc1 wave power attenuates with increasing distance from L=3, supporting the idea that the CSES observes the wave activities near the injection region. The observations are unique in that the Pc1 waves are observed in the ionosphere in nearly conjugate regions where transverse Alfvén waves propagate down into the ionosphere.

Diagnosing low-/mid-latitude ionospheric currents using platform magnetometers: CryoSat-2 and GRACE-FO

“…To name a few, we have solar quiet (Sq) currents flowing in the ionospheric E-layer (Yamazaki and Maute 2017), inter-hemispheric field-aligned currents (IHFACs) connecting the two Sq systems in respective hemispheres (Shinbori et al 2017;Lühr et al 2015Lühr et al , 2019, gravity-driven horizontal currents (Lühr and Maus 2006;Maute and Richmond 2017), pressure-driven currents which counter-balance plasma density inhomogeneity (Lühr et al 2003;Stolle et al 2006;Alken et al 2016;Maute and Richmond 2017;Rodríguez-Zuluaga et al 2019;Laundal et al 2019), wind-driven dynamo currents flowing vertically in the ionospheric F-layer (Lühr and Maus 2006), horizontal currents across the polar cap closing net auroral FACs (Lühr and Zhou 2020, and references therein), and low-/mid-latitude small-scale FACs resulting from a divergence of background currents by ionospheric irregularities (Park et al 2009;Rodríguez-Zuluaga et al 2017;Yin et al 2019). There also exist magneto-hydrodynamic (MHD) waves propagating in the ionosphere and accompanying currents, such as Pc3 (Heilig and Sutcliffe 2016) and Pc1 pulsations (Kim et al 2018;Gou et al 2020).…”

Topside Ionospheric Structures Determined via Automatically Detected DEMETER Ion Perturbations during a Geomagnetically Quiet Period

“…In Figure 2, it is clear that the distributions of plasma variations in light of the Kp index present no special areas where PERs with large Kp values appear collectively, although solar activity tends to have a slightly heavier effect on equatorial and high-latitude ionospheric areas. The response of the ionosphere to solar and geomagnetic activity variations depends on the season, latitude, and storm time occurrence [15,32,44,47,48]. In total, 117,718 ion PERs were attained from the ion density dataset measured by the DEMETER satellite during this considered period.…”

Topside Ionospheric Structures Determined by Automatically Detected DEMETER Ion Perturbations

“…Figure 2 shows the distributions of all 117,718 ion PERs with an increasing value of corresponding Kp index as one PER occurred. From Figure 2, it is clear that the distributions of plasma variations in light of Kp index present no special areas, where PERs with large Kp values appear collectively although the solar activity tends to give a more heavier effect on equatorial and high latitude ionospheric areas: the effect from the magnetic storms are global [33,43,44,48]. To further examine exactly the influence of the solar activity on amplitude and space size of ionospheric PERs, firstly, PERs with Kp > 4 considered perturbed period and ones with Kp ≤ 2 for quiet period have been selected respectively from all 117,718 ion PERs to form two new groups of PERs: 87,057 with Kp ≤ 2 and 4,263 with Kp > 4.…”