scholarly journals Multi-scale observations of magnetotail flux transport during IMF-northward non-substorm intervals

2007 ◽  
Vol 25 (7) ◽  
pp. 1709-1720 ◽  
Author(s):  
A. Grocott ◽  
T. K. Yeoman ◽  
S. E. Milan ◽  
O. Amm ◽  
H. U. Frey ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Plasma Sheet ◽  
Plasma Convection ◽  
Flux Transport ◽  
Multi Scale ◽  
Central Plasma ◽  
Central Plasma Sheet ◽  
Field Lines

Abstract. Simultaneous observations by the Cluster spacecraft and SuperDARN radars are presented of magnetotail flux transport during northward, but BY-dominated IMF. Two events are discussed, which occurred on 14 August 2004 and 17 September 2005, during intervals of negative and positive IMF BY, respectively. During both intervals the Cluster spacecraft observed isolated bursts of Earthward plasma convection in the central plasma sheet. During the first event, the flows observed by Cluster also had a significant V⊥Y component in the duskward direction, consistent with westward azimuthal flows observed in the midnight sector by the Northern Hemisphere SuperDARN radars. During the second event, Cluster 4 observed a significant dawnward V⊥Y component, again consistent with the Northern Hemisphere SuperDARN observations which revealed eastward azimuthal flow. In this instance, however, Cluster 3 observed a duskward V⊥Y component which was more consistent with the duskward sense of the convection observed by the Southern Hemisphere SuperDARN radars. This implies that Cluster 3 and Cluster 4 were located on different field lines which experienced opposite net azimuthal forces and hence observed oppositely directed convection. These observations are consistent with previous SuperDARN studies of nightside flows under northward IMF and, more importantly, provide the first simultaneous in-situ evidence for a mode of tail reconnection occurring during non-substorm intervals in an asymmetric tail.

scholarly journals The storm time central plasma sheet

2002 ◽  
Vol 20 (11) ◽  
pp. 1737-1741 ◽  
Author(s):  
R. Schödel ◽  
K. Dierschke ◽  
W. Baumjohann ◽  
R. Nakamura ◽  
T. Mukai
Keyword(s):  
Magnetic Flux ◽  
Plasma Sheet ◽  
Neutral Line ◽  
Magnetic Storms ◽  
Main Phase ◽  
Plasma Convection ◽  
Flux Transport ◽  
Storm Main Phase ◽  
Central Plasma ◽  
Central Plasma Sheet

Abstract. The plasma sheet plays a key role during magnetic storms because it is the bottleneck through which large amounts of magnetic flux that have been eroded from the dayside magnetopause have to be returned to the dayside magnetosphere. Using about five years of Geotail data we studied the average properties of the near- and midtail central plasma sheet (CPS) in the 10–30 RE range during magnetic storms. The earthward flux transport rate is greatly enhanced during the storm main phase, but shows a significant earthward decrease. Hence, since the magnetic flux cannot be circulated at a sufficient rate, this leads to an average dipolarization of the central plasma sheet. An increase of the specific entropy of the CPS ion population by a factor of about two during the storm main phase provides evidence for nonadiabatic heating processes. The direction of flux transport during the main phase is consistent with the possible formation of a near-Earth neutral line beyond ~20 RE.Key words. Magnetospheric physics (plasma convection; plasma sheet; storms and substorms)

scholarly journals Plasma convection in the magnetotail lobes: statistical results from Cluster EDI measurements

2008 ◽  
Vol 26 (8) ◽  
pp. 2371-2382 ◽  
Author(s):  
S. Haaland ◽  
G. Paschmann ◽  
M. Förster ◽  
J. Quinn ◽  
R. Torbert ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Geomagnetic Disturbance ◽  
Plasma Convection ◽  
Data Set ◽  
Central Plasma ◽  
Strong Convection ◽  
Central Plasma Sheet ◽  
Field Lines ◽  
Convection Patterns

Abstract. A major part of the plasma in the Earth's magnetotail is populated through transport of plasma from the solar wind via the magnetotail lobes. In this paper, we present a statistical study of plasma convection in the lobes for different directions of the interplanetary magnetic field and for different geomagnetic disturbance levels. The data set used in this study consists of roughly 340 000 one-minute vector measurements of the plasma convection from the Cluster Electron Drift Instrument (EDI) obtained during the period February 2001 to June 2007. The results show that both convection magnitude and direction are largely controlled by the interplanetary magnetic field (IMF). For a southward IMF, there is a strong convection towards the central plasma sheet with convection velocities around 10 km s−1. During periods of northward IMF, the lobe convection is almost stagnant. A By dominated IMF causes a rotation of the convection patterns in the tail with an oppositely directed dawn-dusk component of the convection for the northern and southern lobe. Our results also show that there is an overall persistent duskward component, which is most likely a result of conductivity gradients in the footpoints of the magnetic field lines in the ionosphere.

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

2006 ◽  
Vol 24 (8) ◽  
pp. 2227-2242 ◽  
Author(s):  
H. Hu ◽  
T. K. Yeoman ◽  
M. Lester ◽  
R. Liu ◽  
H. Yang ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
High Latitude ◽  
Closed Field ◽  
Flow Data ◽  
Plasma Convection ◽  
Convection Pattern ◽  
Reconnection Rate ◽  
Northern Hemispheric ◽  
Field Lines

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 Bx 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 SuperDARN 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.

scholarly journals Rapid flux transport in the central plasma sheet

2001 ◽  
Vol 106 (A1) ◽  
pp. 301-313 ◽  
Author(s):  
R. Schödel ◽  
W. Baumjohann ◽  
R. Nakamura ◽  
V. A. Sergeev ◽  
T. Mukai
Keyword(s):  
Plasma Sheet ◽  
Flux Transport ◽  
Central Plasma ◽  
Central Plasma Sheet

scholarly journals On energetic electrons (>38 keV) in the central plasma sheet: Data analysis and modeling

2011 ◽  
Vol 116 (A9) ◽  
pp. n/a-n/a ◽  
Author(s):  
Bingxian Luo ◽  
Weichao Tu ◽  
Xinlin Li ◽  
Jiancun Gong ◽  
Siqing Liu ◽  
...  
Keyword(s):  
Data Analysis ◽  
Plasma Sheet ◽  
Energetic Electrons ◽  
Central Plasma ◽  
Central Plasma Sheet

scholarly journals In situ observations of aerosol particles remaining from evaporated cirrus crystals: Comparing clean and polluted air masses

2002 ◽  
Vol 2 (5) ◽  
pp. 1599-1633 ◽  
Author(s):  
M. Seifert ◽  
J. Ström ◽  
R. Krejci ◽  
A. Minikin ◽  
A. Petzold ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Aerosol Particles ◽  
Pollution Level ◽  
Size Distributions ◽  
Number Density ◽  
Particle Volume ◽  
The North ◽  
In Situ Observations

Abstract. In situ observations of aerosol particles contained in cirrus crystals are presented and compared to interstitial aerosol size distributions (non-activated particles in between the cirrus crystals). The observations were conducted in cirrus clouds in the Southern and Northern Hemisphere mid-latitudes during the INCA project. The first campaign in March and April 2000 was performed from Punta Arenas, Chile (54° S) in pristine air. The second campaign in September and October 2000 was performed from Prestwick, Scotland (53° N) in the vicinity of the North Atlantic flight corridor. Size distribution measurements of crystal residuals (particles remaining after evaporation of the crystals) show that small aerosol particles (Dp < 0.1µm) dominate the number density of residuals. The crystal residual size distributions were significantly different in the two campaigns. On average the residual size distributions were shifted towards larger sizes in the Southern Hemisphere. For a given integral residual number density, the calculated particle volume was on average three times larger in the Southern Hemisphere. This may be of significance to the vertical redistribution of aerosol mass by clouds in the tropopause region. In both campaigns the mean residual size increased with increasing crystal number density. The observations of ambient aerosol particles were consistent with the expected higher pollution level in the Northern Hemisphere. The fraction of residual particles only contributes to approximately a percent or less of the total number of particles, which is the sum of the residual and interstitial particles.

scholarly journals Energetic ions scattered into the loss cone with observations of the Cluster satellite

2016 ◽  
Vol 34 (2) ◽  
pp. 249-257 ◽  
Author(s):  
Ying Xiong ◽  
Zhigang Yuan ◽  
Jingfang Wang
Keyword(s):  
Field Line ◽  
Plasma Sheet ◽  
Outer Boundary ◽  
Scattering Mechanism ◽  
Loss Cone ◽  
Energetic Ions ◽  
Left Hand ◽  
Central Plasma ◽  
Emic Waves

Abstract. In this paper, we report in situ observations by the Cluster spacecraft of energetic ions scattered into the loss cone during the inbound pass from the plasma sheet into the plasmasphere. During the inbound pass of the plasma sheet, Cluster observed the isotropy ratio of energetic ions to gradually decrease from unity and the isotropic boundary extended to lower L value for higher-energy ions, implying that the field line curvature scattering mechanism is responsible for the scattered ions into the loss cone from the plasma sheet. In the outer boundary of a plasmasphere plume, Cluster 3 observed the increase of the isotropy ratio of energetic ions accompanied by enhancements of Pc2 waves with frequencies between the He+ ion gyrofrequency and O+ ion gyrofrequency estimated in the equatorial plane. Those Pc2 waves were left-hand circularly polarized and identified as electromagnetic ion cyclotron (EMIC) waves. Using the observed parameters, the calculations of the pitch angle diffusion coefficients for ring current protons demonstrate that EMIC waves could be responsible for the ions scattering and loss-cone filling. Our observations provide in situ evidence of energetic ion loss in the plasma sheet and the plasmasphere plume. Our results suggest that energetic ions scattering into the loss cone in the central plasma sheet and the outer boundary of the plasmaspheric plume are attributed to the field line curvature scattering mechanism and EMIC wave scattering mechanism, respectively.

Sign in / Sign up

Export Citation Format

Share Document