Low‐altitude observations and modeling of quasi‐steady magnetopause reconnection

Onsager, T. G.; Chang, S.-W.; Perez, J. D.; Austin, J. B.; Janoo, Laurence X.

doi:10.1029/94ja02702

Cited by 66 publications

(79 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is necessary to maintain change neutrality. Onsager et al (1995) have noted the importance of the ionospheric source of electrons in maintaining charge neutrality. We also noted that recently small uxes of very energetic ions ($200 keV) have been detected by the POLAR satellite on open cusp-like ®eld lines (Spence, private communication).…”

Section: Implications and Interpretation Of The New Observationsmentioning

confidence: 99%

The ionospheric response to flux transfer events: the first few minutes

Rodger

Pinnock

1997

Ann. Geophys.

View full text Add to dashboard Cite

Abstract. We utilise high-time resolution measurements from the PACE HF radar at Halley, Antarctica to explore the evolution of the ionospheric response during the ®rst few minutes after enhanced reconnection occurs at the magnetopause. We show that the plasma velocity increases associated with¯ux transfer events (FTEs) occur ®rst $100±200 km equatorward of the region to which magnetosheath (cusp) precipitation maps to the ionosphere. We suggest that these velocity variations start near the ionospheric footprint of the boundary between open and closed magnetic ®eld lines. We show that these velocity variations have rise times $100 s and fall times of $10 s. When these velocity transients reach the latitude of the cusp precipitation, sometimes the equatorward boundary of the precipitation begins to move equatorward, the expected and previously reported ionospheric signature of enhanced reconnection. A hypothesis is proposed to explain the velocity variations. It involves the rapid out¯ow of magnetospheric electrons into the magnetosheath along the most recently reconnected ®eld lines. Several predictions are made arising from the proposed explanation which could be tested with ground-based and space-based observations.

show abstract

Section: Implications and Interpretation Of The New Observationsmentioning

confidence: 99%

The ionospheric response to flux transfer events: the first few minutes

Rodger

Pinnock

1997

Ann. Geophys.

View full text Add to dashboard Cite

show abstract

“…For example, the merging process has been believed to be quasistationary (e.g. Onsager et al, 1995;Fuselier et al, 2000;Frey et al, 2002Frey et al, , 2003Chang et al, 2004), while Chisham et al (2004) noted reconnection potential with transient enhancements. Lu et al (2004) observed intermittent magnetic reconnection at the high-latitude magnetopause, and Provan et al (2005) suggested that the dayside reconnection rate was modulated by variations in the solar wind dynamic pressure and the IMF B z component.…”

Section: ∼30 • -40mentioning

confidence: 99%

Dayside flow bursts and high-latitude reconnection when the IMF is strongly northward

Yeoman²,

Lester³

et al. 2006

Ann. Geophys.

View full text Add to dashboard Cite

Abstract. The characteristics of dayside ionospheric convection are studied using Northern Hemispheric SuperDARN data and DMSP particle and flow observations when the interplanetary magnetic field (IMF) was strongly northward during 13:00-15:00 UT on 2 March 2002. Although IMF B x was positive, which is believed to favour Southern Hemisphere high-latitude reconnection at equinox, a four-cell convection pattern was observed and lasted for more than 1.5 h in the Northern Hemisphere. The reconnection rate derived from an analysis of the Northern Hemisphere Super-DARN data illustrates that the high-latitude reconnection was quasi-periodic, with a period between 4-16 min. A sawtooth-like and reverse-dispersed ion signature was observed by DMSP-F14 in the sunward cusp convection at around 14:41 UT, confirming that the high-latitude reconnection was pulsed. Accompanying the pulsed reconnection, strong antisunward ionospheric flow bursts were observed in the post-noon LLBL region on closed field lines, propagating with the same speed as the plasma convection. DMSP flow data show that a similar flow pattern and particle precipitation occurred in the conjugate Southern Hemisphere.

show abstract

“…While statistical plasma properties of the LLBL and cusp regions have been extensively studied (e.g., Smith and Lockwood, 1996;Meng, 1988, 1992;Onsager et al, 1995;Lockwood and Smith, 1994;Lockwood et al, 1998;Aparicio et al, 1991;Newell et al, 1991a,b;Lundin, 1992, 1993;Zhou et al, 2000), the electron edge of the LLBL containing only magnetosheath-like electrons is a comparatively poorly studied region. However, Wing et al (1996) and Wing et al (2005) modelled the penetration of the magnetosheath electrons to low altitudes and compared results from these models with DMSP observations.…”

Section: Introductionmentioning

confidence: 99%

Statistical study of the location and size of the electron edge of the Low-Latitude Boundary Layer as observed by Cluster at mid-altitudes

et al. 2006

View full text Add to dashboard Cite

Abstract. The nature of particle precipitations at dayside mid-altitudes can be interpreted in terms of the evolution of reconnected field lines. Due to the difference between electron and ion parallel velocities, two distinct boundary layers should be observed at mid-altitudes between the boundary between open and closed field lines and the injections in the cusp proper. At lowest latitudes, the electrondominated boundary layer, named the "electron edge" of the Low-Latitude Boundary Layer (LLBL), contains softmagnetosheath electrons but only high-energy ions of plasma sheet origin. A second layer, the LLBL proper, is a mixture of both ions and electrons with characteristic magnetosheath energies. The Cluster spacecraft frequently observe these two boundary layers. We present an illustrative example of a Cluster mid-altitude cusp crossing with an extended electron edge of the LLBL. This electron edge contains 10-200 eV, low-density, isotropic electrons, presumably originating from the solar wind halo population. These are occasionally observed with bursts of parallel and/or anti-paralleldirected electron beams with higher fluxes, which are possibly accelerated near the magnetopause X-line. We then use 3 years of data from mid-altitude cusp crossings (327 events) to carry out a statistical study of the location and size of the electron edge of the LLBL. We find that the equatorward boundary of the LLBL electron edge is observed at 10:00-17:00 magnetic local time (MLT) and is located typically between 68 • and 80 • invariant latitude (ILAT). The location of the electron edge shows a weak, but significant, dependence on some of the external parameters (solar wind pressure, and IMF B Z -component), in agreement with expectations from previous studies of the cusp location. The latitudinal extent of the electron edge has been estimated using new multi-spacecraft techniques. The Cluster tetrahedron crosses the electron and ion boundaries of the LLBL/cusp Correspondence to: Y. V. Bogdanova (jb@mssl.ucl.ac.uk) with time delays of 1-40 min between spacecraft. We reconstruct the motion of the electron boundary between observations by different spacecraft to improve the accuracy of the estimation of the boundary layer size. In our study, the LLBL electron edge is distinctly observed in 87% of mid-altitude LLBL/cusp crossings with clear electron and ion equatorward boundaries equivalent to 35% of all LLBL/cusp crossings by Cluster. The size of this region varied between 0 • -2 • ILAT with a median value of 0.2 • ILAT. Generally, the size of the LLBL electron edge depends on the combination of many parameters. However, we find an anti-correlation between the size of this region and the strength of the IMF, the absolute values of the IMF B Y -and B Z -components and the solar wind dynamic pressure, as is expected from a simple reconnection model for the origin of this region.

show abstract

Low‐altitude observations and modeling of quasi‐steady magnetopause reconnection

Cited by 66 publications

References 35 publications

The ionospheric response to flux transfer events: the first few minutes

The ionospheric response to flux transfer events: the first few minutes

Dayside flow bursts and high-latitude reconnection when the IMF is strongly northward

Statistical study of the location and size of the electron edge of the Low-Latitude Boundary Layer as observed by Cluster at mid-altitudes

Contact Info

Product

Resources

About