Energetic ions in the high latitude boundary layer of the magnetosphere—Rapid/Cluster observation

2003 ◽  
pp. 101-110 ◽  
Author(s):  
Q.-G. Zong ◽  
T. A. Fritz ◽  
B. Wilken ◽  
P. Daly
Keyword(s):  
Boundary Layer ◽  
High Latitude ◽  
Energetic Ions

scholarly journals Recirculation of plasma sheet particles into the high-latitude boundary layer

1998 ◽  
Vol 103 (A11) ◽  
pp. 26521-26532 ◽  
Author(s):  
D. C. Delcourt ◽  
J.-A. Sauvaud
Keyword(s):  
Boundary Layer ◽  
High Latitude ◽  
Plasma Sheet

scholarly journals Channelling of high-latitude boundary-layer flow

2008 ◽  
Vol 15 (1) ◽  
pp. 33-52 ◽  
Author(s):  
N. Nawri ◽  
R. E. Stewart
Keyword(s):  
Boundary Layer ◽  
High Latitude ◽  
Large Scale ◽  
Dynamical Downscaling ◽  
Geostrophic Wind ◽  
Horizontal Wind ◽  
Stationary States ◽  
Prevailing Wind ◽  
Surface Winds ◽  
Variable Surface

Abstract. Due to the stability of the boundary-layer stratification, high-latitude winds over complex terrain are strongly affected by blocking and channelling effects. Consequently, at many low-lying communities in the Canadian Archipelago, including Cape Dorset and Iqaluit considered in this study, surface winds for the most part are from two diametrically opposed directions, following the orientation of the elevated terrain. Shifts between the two prevailing wind directions can be sudden and are associated with geostrophic wind directions within a well defined narrow range. To quantitatively investigate the role of large-scale pressure gradients and the quasi-geostrophic overlying flow, an idealised dynamical system for the evolution of channelled surface winds is derived from the basic equations of motion, in which stability of stationary along-channel wind directions is described as a function of the geostrophic wind. In comparison with long-term horizontal wind statistics at the two locations it is shown that the climatologically prevailing wind directions can be identified as stationary states of the idealised wind model, and that shifts between prevailing wind directions can be represented as stability transitions between these stationary states. In that sense, the prevailing local wind conditions can be interpreted as attracting states of the actual flow, with observed surface winds adjusting to a new stable direction as determined by the idealised system within 3–9 h. Over these time-scales and longer it is therefore advantageous to determine the relatively slow evolution of the observationally well-resolved large-scale pressure distribution, instead of modelling highly variable surface winds directly. The simplified model also offers a tool for dynamical downscaling of global climate simulations, and for determining future scenarios for local prevailing wind conditions. In particular, it allows an estimation of the sensitivity of local low-level winds to changes in the large-scale atmospheric circulation.

The Layered Structure of the Winter Atmospheric Boundary Layer in the Interior of Alaska

2013 ◽  
Vol 52 (4) ◽  
pp. 953-973 ◽  
Author(s):  
John A. Mayfield ◽  
Gilberto J. Fochesatto
Keyword(s):  
Boundary Layer ◽  
Statistical Analysis ◽  
Atmospheric Boundary Layer ◽  
Layered Structure ◽  
High Latitude ◽  
Meteorological Conditions ◽  
Formation Mechanisms ◽  
Observation Data ◽  
Interior Alaska ◽  
Radiosonde Observation

AbstractThe high-latitude winter atmospheric boundary layer of interior Alaska continually exhibits a complex layered structure as a result of extreme meteorological conditions. In this paper the occurrence of elevated inversions (EI), surface-based inversions (SBI), and stratified layers in the sub-Arctic from January 2000 to December 2009 is reported. This statistical analysis is based on radiosonde observation data from the Fairbanks National Weather Service station complemented by Winter Boundary Layer Experiment observations in the period 2010–11. This study found that SBIs occurred 64% of the time. An SBI occurred in combination with one, two, three, or four simultaneous EIs 84.86%, 48.49%, 21.23%, and 7.99% of the time, respectively, in 2326 total cases. The calculated mean SBI height was 377 m; EIs occurred at 1231, 2125, 2720, and 3125 m, respectively. This analysis was able to discriminate between locally controlled inversion layers and synoptic-dependent inversions and to identify their formation mechanisms. It was found that, in the presence of an SBI layer, the first EI layer formed 35.8% of the time under anticyclonic conditions at a mean height of 1249 m and 22% of the time in warm-air-advection situations at a mean height of 1049 m. The remaining 23.4% resulted from combined synoptic situations, and 18.8% were unclassified.

scholarly journals Cluster observations of bounday layer structure and a flux transfer event near the cusp

2005 ◽  
Vol 23 (7) ◽  
pp. 2605-2620 ◽  
Author(s):  
R. C. Fear ◽  
A. N. Fazakerley ◽  
C. J. Owen ◽  
A. D. Lahiff ◽  
E. A. Lucek ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Latitude ◽  
Layer Structure ◽  
Normal Component ◽  
Transfer Event ◽  
Flux Transfer Events ◽  
Magnetic Signatures ◽  
Northern High Latitude ◽  
Flux Transfer ◽  
The Magnetic Field

Abstract. On the 25th January 2002 between 10:00 and 12:00 UT, the four Cluster spacecraft passed through the northern high-latitude cusp, the dayside magnetosphere and into the magnetosheath in a linear formation. In the magnetosphere the PEACE electron spectrometers on the four spacecraft all observed a series of transient bursts of magnetosheath-like plasma, but without bipolar magnetic signatures in the magnetopause normal component as might be expected if the plasma had been injected by transient reconnection (flux transfer events – FTEs). Reordering the data using the magnetopause transition parameter reveals that these plasma observations, the related variations in the magnetic field and the balance of magnetic and thermal gas pressures are consistent with transient entries into a stable high-latitude boundary layer structure. However, once some of the spacecraft entered the magnetosheath, FTE signatures were observed outside the magnetopause at the same time as some of the boundary layer entries occurred at the other spacecraft inside. Thus, (a) the lack of a bipolar BN signature is inconsistent with the traditional picture of a magnetospheric FTE, and (b) the cause of the observed entry of the spacecraft into the boundary layer (pressure pulse or passing magnetosheath FTE) can only be determined by spacecraft observations in the magnetosheath. Keywords. Magnetospheric physics (Magnetopause, cusp and bondary layers; Solar wind- magnetosphere interactions; Magnetosheath)

scholarly journals VLF/ELF wave activity in the vicinity of the polar cusp: Cluster observations

2006 ◽  
Vol 24 (7) ◽  
pp. 1993-2004
Author(s):  
N. Lin ◽  
E. S. Lee ◽  
J. McFadden ◽  
G. Parks ◽  
M. Wilber ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Latitude ◽  
Narrow Band ◽  
Broad Band ◽  
Particle Interaction ◽  
Wave Activity ◽  
Magnetic Noise ◽  
Polar Cusp ◽  
Electrostatic Waves ◽  
Strong Broad Band

Abstract. Observations by the Cluster spacecraft of VLF/ELF wave activity show distinct signatures for different regions in the vicinity of high altitude polar cusps, which are identified by using magnetic field and plasma data along spacecraft trajectories. These waves include: (1) Broad band magnetic noise observed in the polar cusp at frequencies from several Hz to ~100 Hz, below the local electron cyclotron frequency, fce. Similar magnetic noise is also observed in the high latitude magnetosheath and the magnetopause boundary layer. (2) Strong broad band electrostatic emissions observed in the cusp, in the magnetosheath, and in the high latitude magnetopause boundary layer, at frequencies extending from several Hz to tens of kHz, with maximum intensities below ~100 Hz. (3) Narrow-band electromagnetic whistler waves at frequencies ~0.2–0.6 fce, frequently observed in the closed boundary layer (CBL) adjacent to the polar cusp. These waves are for the first time observed in this region to be accompanied by counter-streaming electron beams of ~100 eV, which suggests that the waves are excited by these electrons through wave-particle interaction. (4) Narrow-band electrostatic waves observed slightly above the local fce in the CBL. (5) Lion roars, observed in the high latitude magnetosheath, often in magnetic troughs of mirror mode oscillations. The above wave signatures can serve as indicators of the regions in the vicinity of the magnetospheric cusp.

A high-latitude boundary layer crossing-INTERBALL measurements and MHD model results

1998 ◽  
Vol 22 (1) ◽  
pp. 161-165 ◽  
Author(s):  
B. Nikutowski ◽  
J. Büchner ◽  
H. Wiechen ◽  
U. Auster ◽  
K.H. Fornacon ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Latitude ◽  
Mhd Model

scholarly journals Modeling Kelvin‐Helmholtz Instability at the High‐Latitude Boundary Layer in a Global Magnetosphere Simulation

2021 ◽  
Author(s):  
A. T. Michael ◽  
K. A. Sorathia ◽  
V.G. Merkin ◽  
K. Nykyri ◽  
B. Burkholder ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Latitude ◽  
Helmholtz Instability
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