Ground‐Based Magnetometer Response to Impacting Magnetosheath Jets

Abstract

The terrestrial bow shock is a shock front formed in front of the magnetosphere where the supersonic solar wind abruptly decelerates to subsonic velocities. Downstream of the bow shock lies a turbulent region of warm dense plasma -the magnetosheath. In the magnetosheath, localized dynamic pressure enhancements are often observed examples (Amata et al., 2011;Archer et al., 2012;Karlsson et al., 2012). These pressure enhancements have been referred by many different names, for example, plasmoids (Gunell et al., 2012(Gunell et al., , 2014, antisunward high-speed jets (Plaschke et al., 2020), and supermagnetosonic subsolar magnetosheath jets (Hietala et al., 2012). In this article, we will refer to them as jets, or impacting jets.Geoeffective jets, which are jets causing disturbances to the magnetosphere-ionosphere system, have raised attention. For instance, Hietala et al. (2012) investigated several jets measured during a period of one day by Cluster spacecraft. They compared the jet observations with simultaneous observations from the geostationary orbit by Geostationary Operational Environmental Satellite (GOES) and from the ionosphere by the Super Dual Aurora Network (SuperDARN) radars. Hietala et al. (2012) reported that during times with observations of jets, irregular pulsations in the magnetic field at the geostationary orbit could be seen. Furthermore, at the same time, localized enhanced ionospheric flows were observed by SuperDARN. Archer, Horbury, et al. (2013) performed a similar study using the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft observations and ground-based magnetometer (GMAG) data as well as SuperDARN observations during a time period of 12 h. Also they could observe enhanced ionospheric flows associated with the periods with jet observations. Archer, Horbury, et al. (2013) characterized these flows as traveling convection vortices (TCVs, cf. (Glassmeier et al., 1989)). Further, Archer et al (2013) suggested that the magnetopause filters away pressure variations on timescales shorter than a few minutes, yielding a low-pass filter effect. Dmitriev and Suvorova (2012) conducted a case study for a single jet using THEMIS spacecraft observations and GMAG data. They reported that the magnetosheath jet in their event impacted the magnetopause causing it to distort in an "expansion-compression-expansion" sequence, which lasted for ∼15 min. At the same time, the Chapman-Ferraro currents at the magnetopause were simi-Abstract Localized dynamic pressure pulses in the magnetosheath, or jets, have been a popular topic for discussion in recent decades. Studies show that they can propagate through the magnetosheath and impact the magnetopause, possibly showing up as geoeffective elements at ground level. However, questions still remain on how geoeffective they can be. Previous studies have been limited to case studies during few days and with only a handful of events. In this study we have found 65 cases of impacting jets using observations from the Multisca...

Investigating the Role of Magnetosheath High‐Speed Jets in Triggering Dayside Ground Magnetic Ultra‐Low Frequency Waves

“…These HSJ‐triggered ground magnetic field oscillations is in good agreement with a recent report by Norenius et al. (2021).…”

Magnetosheath Jet Occurrence Rate in Relation to CMEs and SIRs

“…There is the consensus that the jets primarily appear downstream of the quasi‐parallel bow shock (Archer & Horbury, 2013 ; Plaschke et al., 2013 ; Raptis et al., 2020 ; Vuorinen et al., 2019 ). There is evidence that magnetosheath jets significantly influence the magnetopause and cause geomagnetic substorms in Earth's magnetosphere (Hietala et al., 2018 ; Norenius et al., 2021 ; Nykyri et al., 2019 ; Wang et al., 2018 ). Magnetosheath jets are therefore an important link between the SW and the magnetopause.…”

On Magnetosheath Jet Kinetic Structure and Plasma Properties

“…It has been shown that jets appear more frequently behind the Qpar shock rather than the Qperp one (Raptis, Aminalragia‐Giamini, et al., 2020; Raptis, Karlsson, et al., 2020; Vuorinen et al., 2019), and typically have significant effects on the geomagnetic environment of Earth (Plaschke et al., 2018). For example, they can enhance or initiate magnetopause reconnection (Escoubet et al., 2020; Hietala et al., 2018; Ng et al., 2021; Vuorinen et al., 2021), accelerate particles (Liu et al., 2019, 2020), generate a variety of different waves in the MSH and outer magnetosphere environment (Archer et al., 2019, 2021; Katsavrias et al., 2021) and even have effects on the inner magnetosphere and ionosphere (Hietala et al., 2012; Norenius et al., 2021; Wang et al., 2018).…”

“…outer magnetosphere environment (Archer et al, 2019(Archer et al, , 2021Katsavrias et al, 2021) and even have effects on the inner magnetosphere and ionosphere (Hietala et al, 2012;Norenius et al, 2021;Wang et al, 2018).…”