Multi-instrument observations of polar cap patches and traveling ionospheric disturbances generated by solar wind Alfvén waves coupling to the dayside magnetosphere

Abstract

Abstract. During minor to moderate geomagnetic storms, caused by corotating interaction regions (CIRs) at the leading edge of high-speed streams (HSSs), solar wind Alfvén waves modulated the magnetic reconnection at the dayside magnetopause. The Resolute Bay Incoherent Scatter Radars (RISR-C and RISR-N), measuring plasma parameters in the cusp and polar cap, observed ionospheric signatures of flux transfer events (FTEs) that resulted in the formation of polar cap patches. The patches were observed as they moved over the RISR, and the Canadian High-Arctic Ionospheric Network (CHAIN) ionosondes and GPS receivers. The coupling process modulated the ionospheric convection and the intensity of ionospheric currents, including the auroral electrojets. The horizontal equivalent ionospheric currents (EICs) are estimated from ground-based magnetometer data using an inversion technique. Pulses of ionospheric currents that are a source of Joule heating in the lower thermosphere launched atmospheric gravity waves, causing traveling ionospheric disturbances (TIDs) that propagated equatorward. The TIDs were observed in the SuperDual Auroral Radar Network (SuperDARN) high-frequency (HF) radar ground scatter and the detrended total electron content (TEC) measured by globally distributed Global Navigation Satellite System (GNSS) receivers.

Observations of traveling ionospheric disturbances driven by gravity waves from sources in the upper and lower atmosphere

“…In Section 3.2, we present observations of TIDs generated by solar wind-M-I-T coupling on the dayside following the arrival of high-speed streams (HSSs) permeated by solar wind Alfvén waves (Belcher and Davis, 1971;Tsurutani et al, 1987). Solar wind Alfvén waves can modulate ionospheric convection and currents producing polar cap density patches and TIDs (Prikryl et al, 1999(Prikryl et al, , 2005(Prikryl et al, , 2022.…”

“…The Worldwide Atmospheric Gravity-wave Studies (WAGS) program (Crowley and Williams, 1988;Williams et al, 1993) showed that large-scale TIDs originate in auroral latitudes. TIDs generated by AGWs originating in the lower atmosphere come from a variety of sources, including tropospheric weather systems (Bertin, Testud and Kersley, 1975;Bertin et al, 1978;Waldock and Jones, 1987;Oliver et al, 1997;Nishioka et al, 2013;Azeem et al, 2015), total solar eclipses (Zhang et al, 2017;Mrak et al, 2018), the polar vortex (Frissell et al, 2016), volcanic eruptions, earthquakes, and tsunamis (Yu, Wang and Hickey, 2017;Nishitani et al, 2019;Themens et al, 2022).…”

“…The solar wind coupling to the dayside magnetosphere (Dungey, 1961(Dungey, , 1995 generates variable electric fields that map to the ionosphere driving the E×B ionospheric convection and currents. The Joule heating due to the ionospheric currents of in the lower thermosphere is a source of equatorward propagating AGWs, which in turn drive TIDs (e.g., Prikryl et al, 2022). The electric fields transmitted to the low latitude ionosphere in the magnetosphere-ionosphere current circuit (Kikuchi and Hashimoto, 2016) play a role in generating TIDs through ion-neutral interactions (Nishitani et al, 2019) and an electrodynamic instability mechanism (Kelley et al, 2023).…”

“…Global Navigation Satellite System (GNSS) data for this were gathered from the same global networks of GNSS receivers used in Themens et al (2022), which constitute 5200-5800 stations, depending on the period. Examples of the GNSS station distribution in the two local domains can be viewed in Fig.…”

“…To characterize the TID structures using these data, LoS TEC measurements for each satellitereceiver pair were detrended by first projecting the LoS TEC to vertical TEC (vTEC) using the thin shell approximation at 350-km altitude and subtracting the sliding 60-minute average. More details on this method can be found in Themens et al (2022). The TEC anomalies are then binned in 0.75-degree latitude and longitude bins for mapping.…”