Statistical Study of Foreshock Transients in the Midtail Foreshock

Liu, Zixu; Zhang, Hui; Wang, Chih‐Ping; Angelopoulos, V.; Vu, Andrew; Wang, Xueyi; Lin, Y.

doi:10.1029/2021ja029156

Cited by 16 publications

(34 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As for the Mach numbers, Figure 3e of the Alfvén Mach numbers shows an increasing preference for higher Alfvén Mach numbers for all event types and peaks between 11 and 13 Alfvén Mach numbers, after which the occurrence rates decrease, consistent with Facskó et al (2009) and Liu, Zhang, Wang, et al (2021). The same trend holds qualitatively after calculating the local the Alfvén Mach number at the local bow shock surface, shown in Figure 3f.…”

Section: Solar Wind Conditions Of Eventssupporting

confidence: 57%

Statistical Study of Foreshock Bubbles, Hot Flow Anomalies, and Spontaneous Hot Flow Anomalies and Their Substructures Observed by MMS

Liu

Zhang

et al. 2022

JGR Space Physics

Self Cite

View full text Add to dashboard Cite

Ubiquitous throughout the universe, shocks form when a supersonic flow encounters an obstacle and are important particle accelerators through different acceleration mechanisms (e.g., Helder et al., 2012;Lee et al., 2012). On Earth, a bow shock forms when the supermagnetosonic solar wind encounters the magnetosphere. At the quasi-parallel bow shock (where the angle between the shock normal and the interplanetary magnetic field (IMF) is less than 45°), some solar wind particles are reflected by the bow shock and populate the region upstream known as the foreshock (e.g., Eastwood et al., 2005). Interactions between these foreshock particles and the incoming solar wind particles can generate ULF waves that permeate the foreshock (e.g., Eastwood et al., 2005;Wilson et al., 2016). In addition, transient kinetic phenomena are also observed in the foreshock (see review by Zhang et al., 2022), such as hot flow anomalies (HFAs) (

show abstract

Section: Solar Wind Conditions Of Eventssupporting

confidence: 57%

Statistical Study of Foreshock Bubbles, Hot Flow Anomalies, and Spontaneous Hot Flow Anomalies and Their Substructures Observed by MMS

Liu

Zhang

et al. 2022

JGR Space Physics

Self Cite

View full text Add to dashboard Cite

show abstract

“…This could explain why in Liu, Turner, et al. (2016), a thick TD forms an HFA, and a thin TD forms an FB during the same time interval, and why a larger magnetic shear angle favors the formation of HFAs (e.g., Liu et al., 2021; Schwartz et al., 2000; Zhao et al., 2017).…”

Section: Discussionmentioning

confidence: 99%

Hybrid Simulations of a Tangential Discontinuity‐Driven Foreshock Bubble Formation in Comparison With a Hot Flow Anomaly Formation

Liu

Zhang

et al. 2022

JGR Space Physics

Self Cite

View full text Add to dashboard Cite

Hot flow anomalies (HFAs) and foreshock bubbles (FBs) are significant foreshock transients that can accelerate particles and disturb the magnetosphere‐ionosphere system. Yet, their early formation mechanisms are still not fully understood. To investigate the formation of tangential discontinuity (TD)‐driven FBs and HFAs, we use 2‐D local hybrid simulations where a reflected or an injected warm foreshock ion beam can interact with a TD whose half‐thickness is comparable to the ion inertial scale. We show that the foreshock ions perform a partial gyration within, or across, the TD. Bulk motion differences between partially‐gyrating foreshock ions and fluid‐electrons lead to the generation of currents. As the trigger, these foreshock‐driven currents change the magnetic field topology around the TD and force the frozen‐in solar wind plasma to redistribute along with the field lines, shaping the foreshock transient. This confirms a recently proposed kinetic formation model. The extent of the magnetic field direction change across the TD within the foreshock ion gyromotion determines the current profile and thus the type of foreshock transient that forms. For a thin TD, the foreshock ions generate a current that is much stronger on the upstream side than the downstream side, forming an FB with one upstream compressional boundary. For the same foreshock ion gyroradius and magnetic shear, a thick TD yields comparable foreshock‐driven currents on the upstream and downstream sides, forming an HFA with two compressional boundaries. Our study suggests that the TD thickness is one of the factors that determine the formation of FBs and HFAs.

show abstract

“… 2017b ) and ARTEMIS (Liu et al. 2021 ) observations also found that the solar wind density does not affect the HFA, SHFA, and FB occurrence, but that low IMF strengths favor occurrence. High fast magnetosonic Mach number ( ) also favors the formation of HFAs.…”

Section: Transient Processes In the Foreshock Bow Shock And Magnetosh...mentioning

confidence: 93%

“…The statistical study of foreshock transients in the midtail foreshock also showed that high solar wind Alfvén Mach number is a favorable condition (Liu et al. 2021 ). PIC simulations by An et al.…”

Section: Transient Processes In the Foreshock Bow Shock And Magnetosh...mentioning

confidence: 98%

Dayside Transient Phenomena and Their Impact on the Magnetosphere and Ionosphere

et al. 2022

Self Cite

View full text Add to dashboard Cite

Dayside transients, such as hot flow anomalies, foreshock bubbles, magnetosheath jets, flux transfer events, and surface waves, are frequently observed upstream from the bow shock, in the magnetosheath, and at the magnetopause. They play a significant role in the solar wind-magnetosphere-ionosphere coupling. Foreshock transient phenomena, associated with variations in the solar wind dynamic pressure, deform the magnetopause, and in turn generates field-aligned currents (FACs) connected to the auroral ionosphere. Solar wind dynamic pressure variations and transient phenomena at the dayside magnetopause drive magnetospheric ultra low frequency (ULF) waves, which can play an important role in the dynamics of Earth’s radiation belts. These transient phenomena and their geoeffects have been investigated using coordinated in-situ spacecraft observations, spacecraft-borne imagers, ground-based observations, and numerical simulations. Cluster, THEMIS, Geotail, and MMS multi-mission observations allow us to track the motion and time evolution of transient phenomena at different spatial and temporal scales in detail, whereas ground-based experiments can observe the ionospheric projections of transient magnetopause phenomena such as waves on the magnetopause driven by hot flow anomalies or flux transfer events produced by bursty reconnection across their full longitudinal and latitudinal extent. Magnetohydrodynamics (MHD), hybrid, and particle-in-cell (PIC) simulations are powerful tools to simulate the dayside transient phenomena. This paper provides a comprehensive review of the present understanding of dayside transient phenomena at Earth and other planets, their geoeffects, and outstanding questions.

show abstract

Statistical Study of Foreshock Transients in the Midtail Foreshock

Cited by 16 publications

References 61 publications

Statistical Study of Foreshock Bubbles, Hot Flow Anomalies, and Spontaneous Hot Flow Anomalies and Their Substructures Observed by MMS

Statistical Study of Foreshock Bubbles, Hot Flow Anomalies, and Spontaneous Hot Flow Anomalies and Their Substructures Observed by MMS

Hybrid Simulations of a Tangential Discontinuity‐Driven Foreshock Bubble Formation in Comparison With a Hot Flow Anomaly Formation

Dayside Transient Phenomena and Their Impact on the Magnetosphere and Ionosphere

Contact Info

Product

Resources

About