THEMIS observations of a hot flow anomaly: Solar wind, magnetosheath, and ground‐based measurements

Eastwood, J. P.; Sibeck, D. G.; Angelopoulos, V.; Phan, T. D.; Bale, S. D.; McFadden, J. P.; Cully, C. M.; Mende, S. B.; Larson, D. E.; Frey, S.; Carlson, C. W.; Glassmeier, K.; Auster, H. U.; Roux, A.; Contel, O. Le

doi:10.1029/2008gl033475

Cited by 89 publications

(99 citation statements)

References 22 publications

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“…Shields et al (2003) showed statistically that TCV events occur simultaneously with Pc 3 micropulsations and might share the same source as these waves. THEMIS ground-based stations observed a propagating magnetic impulse event caused by an HFA (Eastwood et al 2008), while reported a Pc 5 ULF wave event generated by transient ion foreshock phenomena (TIFP) such as HFAs. Zhao et al (2017b) have shown that HFAs can generate global Pc 3 ULF waves inside the magnetosphere, and that the generated waves are standing Alfvén waves.…”

Section: Ulf Waves Driven By the Transient Foreshock Phenomenamentioning

confidence: 99%

The interaction of ultra-low-frequency pc3-5 waves with charged particles in Earth’s magnetosphere

Zong

Rankin

Zhou

2017

Rev. Mod. Plasma Phys.

140

162

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One of the most important issues in space physics is to identify the dominant processes that transfer energy from the solar wind to energetic particle populations in Earth's inner magnetosphere. Ultra-low-frequency (ULF) waves are an important consideration as they propagate electromagnetic energy over vast distances with little dissipation and interact with charged particles via drift resonance and drift-bounce resonance. ULF waves also take part in magnetosphereionosphere coupling and thus play an essential role in regulating energy flow throughout the entire system. This review summarizes recent advances in the characterization of ULF Pc3-5 waves in different regions of the magnetosphere, including ion and electron acceleration associated with these waves.

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Section: Ulf Waves Driven By the Transient Foreshock Phenomenamentioning

confidence: 99%

The interaction of ultra-low-frequency pc3-5 waves with charged particles in Earth’s magnetosphere

Zong

Rankin

Zhou

2017

Rev. Mod. Plasma Phys.

140

162

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“…Sibeck et al (1999) described magnetopause motion and auroral brightening related to an HFA. Eastwood et al (2008) presented a magnetic impulse event associated with an HFA, which mapped to the dawn flank of the magnetosphere. The HFA pressure perturbation had a significant impact on the magnetopause location, which was measured with ground-based instruments.…”

Section: Introductionmentioning

confidence: 99%

THEMIS satellite observations of hot flow anomalies at Earth's bow shock

et al. 2017

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Abstract. Hot flow anomalies (HFAs) at Earth's bow shock were identified in Time History of Events and Macroscale Interactions During Substorms (THEMIS) satellite data from 2007 to 2009. The events were classified as young or mature and also as regular or spontaneous hot flow anomalies (SHFAs). The dataset has 17 young SHFAs, 49 mature SHFAs, 15 young HFAs, and 55 mature HFAs. They span a wide range of magnetic local times (MLTs) from approximately 7 to 16.5 MLT. The largest ratio of solar wind to HFA core density occurred near dusk and at larger distances from the bow shock. In this study, HFAs and SHFAs were observed up to 6.3 R E and 6.1 R E (Earth radii), respectively, upstream from the model bow shock. HFA-SHFA occurrence decreases with distance upstream from the bow shock. HFAs of the highest event core ion temperatures were not seen at the flanks. The ratio of HFA ion temperature increase to HFA electron temperature increase is highest around 12 MLT and slightly duskward. For SHFAs, (T ihfa /T isw )/(T ehfa /T esw ) generally increased with distance from the bow shock. Both mature and young HFAs are more prevalent when there is an approximately radial interplanetary magnetic field. HFAs occur most preferentially for solar wind speeds from 550 to 600 km s −1 . The correlation coefficient between the HFA increase in thermal energy density from solar wind values and the decrease in kinetic energy density from solar wind values is 0.62. SHFAs and HFAs do not show major differences in this study.

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“…HFAs have magnetosheath manifestations and can impact the magnetopause and magnetosphere (Paschmann et al, 1988;Sibeck et al, 1999;Safránková et al, 2002;Eastwood et al, 2008). The paradigm adopted by most authors at this time is that heated interior plasma results in an overpressure relative to the solar wind, with explosive expansion in the solar wind frame that drives the formation of edge shocks (e.g.…”

Section: Introductionmentioning

confidence: 99%

Foreshock density holes in the context of known upstream plasma structures

et al. 2008

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Abstract. We present case examples of foreshock density holes and results from a statistical survey, which provide additional characterizations of these recently-described structures. Specific effort is made to place these objects into context with well-studied foreshock phenomena, such as hot flow anomalies (HFAs) and large-amplitude magnetic pulsations (SLAMS). Density holes are observed during higherthan-average solar wind speeds (∼620 km s −1 ), have wellcorrelated density and magnetic field intensities, and anticorrelated density and temperature variations. Like HFAs, these structures occur over a wide range of foreshock geometries, suggesting that this is not a determining factor. They are embedded within IMF current sheets, but their crossstructure magnetic shears are considerably lower than for HFAs. When the Cluster spacecraft are widely separated, they are able to measure structure time development, with substantial changes occurring over 10s of seconds, confirming an earlier case study, and possibly indicating short lifetimes as well. We find that density holes can occur in the absence of strong upstream magnetic pulsations and/or density enhancements, which rules out a "wake effect" as the sole explanation for their formation. Most important is the observation that the observed solar wind motional electric fields tend to have components pointing away from the embedding IMF current sheets. Density holes have no connection with magnetic holes and foreshock cavities, and appear not to be early-stage or weakly-formed HFAs.

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THEMIS observations of a hot flow anomaly: Solar wind, magnetosheath, and ground‐based measurements

Cited by 89 publications

References 22 publications

The interaction of ultra-low-frequency pc3-5 waves with charged particles in Earth’s magnetosphere

The interaction of ultra-low-frequency pc3-5 waves with charged particles in Earth’s magnetosphere

THEMIS satellite observations of hot flow anomalies at Earth's bow shock

Foreshock density holes in the context of known upstream plasma structures

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