A Case Study of Near‐Earth Magnetotail Conditions at Substorm and Pseudosubstorm Onsets

Miyashita, Yukinaga; Angelopoulos, V.; Fukui, Kento; Machida, S.

doi:10.1029/2018gl078589

Cited by 6 publications

(14 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figure 3). Similar relation of plasma sheet β to pseudobreakups and substorms was recently found for a single event study of the near‐Earth magnetotail conditions during fast ion flows that originated from X GSM <−21 R E (Miyashita et al, 2018). That is, despite differences in the dipolarization front formation and substorm scenarios between the near‐Earh BICI mechanism and more tailward reconnection events (Angelopoulos et al, 2008; Nagai et al, 2005; Petrukovich et al, 2009), the requirement of higher β eq may well be common for all substorm models.…”

Section: Relevance To Magnetosphere‐ionosphere Couplingsupporting

confidence: 80%

Understanding Spacecraft Trajectories Through Detached Magnetotail Interchange Heads

Panov

Pritchett

2020

JGR Space Physics

View full text Add to dashboard Cite

The kinetic ballooning/interchange instability (BICI) was recently found to produce azimuthally narrow interchange heads extending into the dipole region from a reversed radial gradient of BZ in the near‐Earth magnetotail. In their nonlinear evolution individual heads were predicted to detach from the reversed BZ gradient and grow into transient earthward moving northward magnetic field intensifications (dipolarization fronts; DFs). The distinguished signatures of such fronts would be their oblique propagation and cross‐tail localization due to the finite ky structure of the BICI modes. Simultaneous conjugate observations of DFs by the Time History of Events and Macroscale Interactions during Substorms probes at 11 Earth's radii (RE) downtail and of sudden brightening and growth of individual auroral beads by the all‐sky imagers on the ground have been suggested to be ionospheric signature of detached magnetotail interchange heads (Panov et al., 2019, https://doi.org/10.1029/2019GL083070). Here we compare such DFs with a simulated interchange head during later(detachment)‐stage BICI head development. The comparison reveals similarly structured leading edges and trailing tails in both the observed DFs and the simulated BICI head. We further identify Time History of Events and Macroscale Interactions during Substorms trajectories through the DFs and find that the trajectories were due to oblique (earthward and dawnward) DF propagation. This analysis further supports the idea that BICI indeed releases obliquely propagating azimuthally localized dipolarization fronts in the Earth's magnetotail.

show abstract

Section: Relevance To Magnetosphere‐ionosphere Couplingsupporting

confidence: 80%

Understanding Spacecraft Trajectories Through Detached Magnetotail Interchange Heads

Panov

Pritchett

2020

JGR Space Physics

View full text Add to dashboard Cite

show abstract

“…Since the width of dipolarization fronts may be related to the maximum ion outflow speed in the reconnection jet (Arnold et al, ), the azimuthal size of the corresponding ionospheric current system may also depend on the reconnection jet speed. Reconnection jets with different speed (or alternatively dipolarization fronts with different width) could lead and contribute to pseudo‐breakups and small or global substorms (Miyashita et al, ; Nakamura et al, ).…”

Section: Discussionmentioning

confidence: 99%

Continent‐Wide R1/R2 Current System and Ohmic Losses by Broad Dipolarization‐Injection Fronts

et al. 2019

View full text Add to dashboard Cite

We employ Magnetospheric Multiscale, Geostationary Operational Environmental and Los Alamos National Laboratory satellites, as well as the ground magnetometer networks over Greenland and North America to study a substorm on 9 August 2016 between 9 and 10 UT. We found that during the substorm two earthward flows, whose dipolarization-injection fronts exceeded 6.5 and 4 Earth's radii (R E) in Y GSM , impinged and rebounded from Earth's dipolar field lines at L = 6-7 downtail, where L is the McIlwain number. The impingements and rebounds ended with a substorm current system of downward R1 and upward R2 currents which grew to azimuthally cover the whole North American continent. At the fronts, regions of enhanced negative j•E ′ were formed and peaked toward the end of the impingements. These regions appeared to be conjugate with eastward moving aurora (along the growth phase arc and together with eastward drifting energetic electrons at geosynchronous equatorial orbit), which manifests ionospheric Ohmic losses.

show abstract

“…In particular, such auroral activity is often seen poleward of the most equatorward arc. Miyashita et al () and Motoba et al () presented pseudosubstorm events that were followed by a substorm. Their all‐sky imager data clearly showed that an auroral onset arc developed into wave‐like structure after initial brightening but did not proceed to poleward expansion for the pseudosubstorms, while poleward expansion occurred for the substorms.…”

Section: Introductionmentioning

confidence: 99%

A Statistical Study of Near‐Earth Magnetotail Evolution During Pseudosubstorms and Substorms With THEMIS Data

et al. 2020

Self Cite

View full text Add to dashboard Cite

Pseudosubstorms (pseudobreakups) and substorms are similar phenomena. In terms of auroral morphology, however, the former are not accompanied by poleward expansion, while the latter are. To understand what causes this difference, we studied temporal and spatial development of the near-Earth magnetotail at X = −7 to −11R E around pseudosubstorm and substorm onsets, based on superposed epoch analysis of Time History of Events and Macroscale Interactions during Substorms (THEMIS) data. We find that the earthward flow begins to increase at X = −10 to −11R E just before onset and dipolarization for both pseudosubstorms and substorms, possibly due to near-Earth magnetic reconnection or the preceding relaxation of the thin current sheet in a tailward region, but the earthward flow is slower for pseudosubstorms than for substorms. Dipolarization, together with magnetic field fluctuation, is nearly the same at X = −8R E for both cases, but it is weaker at other distances for pseudosubstorms than for substorms. This result suggests that the current disruption related to dipolarization does not expand tailward and hence auroral poleward expansion does not occur for pseudosubstorms. Furthermore, the total pressure is larger at X = −8 to −11R E for several minutes before onset for substorms than for pseudosubstorms. The total pressure gradient increases more largely after onset for substorms than for pseudosubstorms. We suggest that these differences are important factors for determining whether ballooning instability causing current disruption grows in a wide area, that is, whether the initial action develops into a substorm or subsides as a pseudosubstorm.

show abstract

A Case Study of Near‐Earth Magnetotail Conditions at Substorm and Pseudosubstorm Onsets

Cited by 6 publications

References 37 publications

Understanding Spacecraft Trajectories Through Detached Magnetotail Interchange Heads

Understanding Spacecraft Trajectories Through Detached Magnetotail Interchange Heads

Continent‐Wide R1/R2 Current System and Ohmic Losses by Broad Dipolarization‐Injection Fronts

A Statistical Study of Near‐Earth Magnetotail Evolution During Pseudosubstorms and Substorms With THEMIS Data

Contact Info

Product

Resources

About