Kinetic‐Scale Magnetic Holes Inside Foreshock Transients

Liu, Zixu; Zhang, Hui; Turner, D. L.; Goodrich, K.; An, Xin; Zhang, Xiaojia

doi:10.1029/2021ja029748

Cited by 6 publications

(5 citation statements)

References 84 publications

(132 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Plasma heating and acceleration, common with FBs and HFAs (e.g., Liu, Angelopoulos et al., 2017), are ignored, because our understanding is still not sufficient to quantify them. (b) In our model and hybrid simulations, electrons are assumed to be magnetized fluid, but our recent observations found that electrons can be demagnetized, resulting in a thin current sheet that shapes the field profile (Liu, Zhang, Turner, et al., 2021). Whether the role of electron dynamics is important needs further examination.…”

Section: Discussionmentioning

confidence: 99%

Modeling the Expansion Speed of Foreshock Bubbles

Liu

Zhang

et al. 2023

JGR Space Physics

Self Cite

View full text Add to dashboard Cite

Foreshock transients, including hot flow anomalies (HFAs) and foreshock bubbles (FBs), are frequently observed in the ion foreshock. Their significant dynamic pressure perturbations can disturb the bow shock, resulting in disturbances in the magnetosphere and ionosphere. They can also contribute to particle acceleration at their parent bow shock. These disturbances and particle acceleration caused by the foreshock transients are not yet predictable, however. In this study, we take the first step in establishing a first‐order predictive expansion speed model for FBs (which are simpler than HFAs). Starting with energy conversion from foreshock ions to solar wind ions, we derive the FB expansion speed in the FB's early formation stage and late expansion stage as a function of foreshock and solar wind parameters. We use local hybrid simulations with varying parameters to fit and improve the early stage model and 1D particle‐in‐cell simulations to test the late‐stage model. By comparing model results with Magnetospheric Multiscale (MMS) and Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations, we adjust the late‐stage model and show that it can predict the FB expansion speed. Our study provides a foundation for predictive models of foreshock transient formation and expansion, so that we can eventually forecast their space weather effects and particle acceleration at shocks.

show abstract

Section: Discussionmentioning

confidence: 99%

Modeling the Expansion Speed of Foreshock Bubbles

Liu

Zhang

et al. 2023

JGR Space Physics

Self Cite

View full text Add to dashboard Cite

show abstract

“…Moreover, a couple of these substructures resemble SLAMS in the foreshock but instead appear in series within event cores (see Substructure one in Figure S3 in Supporting Information S1). For substructures that exhibit a negative correlation between the plasma densities and magnetic field strengths, these substructures could be generated by a slow-mode or mirror-mode mechanism that occurs within the event cores (e.g., Liu, Zhang, Turner, et al, 2021). To elaborate, inside the event cores where the magnetic field strengths are typically very low and the plasma are very hot, plasma betas can be very large (e.g., larger than 10).…”

Section: Discussionmentioning

confidence: 99%

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

“…We have investigated a self-consistent electron acceleration process driven by an adiabatic periodic modulation of the electron distribution function. A natural mechanism of such modulation is the dynamics of ultralow-frequency magnetic field structures (e.g., magnetic holes or compressional waves, see Liu et al 2021;Huang et al 2022) that magnetically trap hot electron populations and transport them across the inhomogeneous and dynamical plasma medium near the Earth Figure 6. Evolution of the energy distribution function f E over the period of 1000 adiabatic oscillations.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

“…To run the electron acceleration on the Earth's bow shock, and in many other shocks observed in the heliosphere, cold solar (stellar) wind electrons should be pre-accelerated (see discussion in Morris et al 2022, 2023, andreferences therein) to energies large enough to start being scattered on low-frequency magnetic field fluctuations (see a review of electron shock acceleration in Amano et al 2022;Perri et al 2022). The key role in such pre-acceleration, and further acceleration at the shock, is believed to be played by various magnetic field perturbations at and around the shock front (e.g., Burgess 2006;Guo & Giacalone 2010;Chen et al 2018), which are naturally generated by shock dynamics (e.g., Krasnoselskikh et al 2013;Johlander et al 2016;Wilson 2016;Liu et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Electron Heating by Magnetic Pumping and Whistler-mode Waves

Frantsuzov,

Artemyev,

Shi

et al. 2024

ApJ

View full text Add to dashboard Cite

The investigation of mechanisms responsible for the heating of cold solar wind electrons around the Earth’s bow shock is an important problem in heliospheric plasma physics because such heating is vitally required to run the shock drift acceleration at the bow shock. The prospective mechanism for electron heating is magnetic pumping, which considers electron adiabatic (compressional) heating by ultralow-frequency waves and simultaneous scattering by high-frequency fluctuations. Existing models of magnetic pumping have operated with external sources of such fluctuations. In this study, we generalize these models by introducing the self-consistent electron scattering by whistler-mode waves generated due to the anisotropic electron heating process. We consider an electron population captured within a magnetic trap created by ultralow-frequency waves. Periodical adiabatic heating and cooling of this population drives the generation of whistler-mode waves scattering electrons in the pitch-angle space. The combination of adiabatic heating and whistler-driven scattering provides electron acceleration and the formation of a suprathermal electron population that can further participate in the shock drift acceleration.

show abstract

Kinetic‐Scale Magnetic Holes Inside Foreshock Transients

Cited by 6 publications

References 84 publications

Modeling the Expansion Speed of Foreshock Bubbles

Modeling the Expansion Speed of Foreshock Bubbles

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

Electron Heating by Magnetic Pumping and Whistler-mode Waves

Contact Info

Product

Resources

About