Electron density and conductance in the auroral ionosphere during substorms. Influence of solar wind and plasma sheet state.

2021 ◽  
Author(s):  
Nikita Stepanov ◽  
Victor Sergeev ◽  
Maria Shukhtina ◽  
Yasunobu Ogawa ◽  
Xiangning Chu
Keyword(s):  
Solar Wind ◽  
Electron Density ◽  
Plasma Sheet ◽  
Auroral Ionosphere

scholarly journals Solar wind control of plasma number density in the near-Earth plasma sheet: three-dimensional structure

2008 ◽  
Vol 26 (12) ◽  
pp. 4031-4049 ◽  
Author(s):  
D. Nagata ◽  
S. Machida ◽  
S. Ohtani ◽  
Y. Saito ◽  
T. Mukai
Keyword(s):  
Solar Wind ◽  
Density Dependence ◽  
High Latitude ◽  
Plasma Sheet ◽  
Strong Dependence ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Lower Latitude ◽  
Number Density ◽  
Three Dimensional Structure

Abstract. The plasma number density in the near-Earth plasma sheet depends on the solar wind number density and the north-south component of interplanetary magnetic field (IMF Bz) with time lag and duration of several hours. We examined the three-dimensional structure of such dependences by fitting observations of plasma sheet and solar wind to an empirical model equation. Analyses were conducted separately for northward and southward IMF conditions. Effects of solar wind speed and IMF orientation were also examined by further subdivision of the dataset. Based on obtained results, we discuss (i) the relative contribution of the ionosphere and solar wind to plasma sheet mass supply, (ii) the entry mechanisms for magnetosheath particles, and (iii) the plasma transport in the plasma sheet. We found that solar wind number density dependence is weaker and IMF Bz dependence is stronger for faster solar wind with southward IMF, which suggests the contribution of ionospheric particles. Further from the Earth, different interplanetary conditions result in different structures of solar wind dependence, which indicate different solar wind entry mechanisms: (1) southward IMF results in a strong dependence on solar wind number density in the flank high-latitude region, (2) slow solar wind with northward IMF leads to lower-latitude peaks of solar wind number density dependence in the flank region, (3) fast solar wind with northward IMF results in a strong dependence on solar wind number density at the down-tail dusk flank equator, and (4) solar wind number density dependence is stronger in the downstream of quasi-parallel bow shock. These features are attributable to (1) low-latitude dayside reconnection entry, (2) high-latitude dayside reconnection entry, (3) entry due to decay of Kelvin-Helmholtz vortices, and (4) diffusive entry mediated by kinetic Alfven waves, respectively. Effect of IMF Bz and its time lags show plasma sheet reconfiguration associated with enhanced convective transport under southward IMF. Duration of IMF Bz effect under northward IMF is interpreted in terms of turbulent diffusive transport.

scholarly journals Cold and Dense Plasma Sheet Caused by Solar Wind Entry: Direct Evidence

Atmosphere ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 831
Author(s):  
Yue Yu ◽  
Zuzheng Chen ◽  
Fang Chen
Keyword(s):  
Solar Wind ◽  
Plasma Sheet ◽  
Cross Correlation ◽  
Direct Evidence ◽  
Dense Plasma ◽  
Ion Density ◽  
Average Value ◽  
Magnetospheric Multiscale ◽  
Cross Correlation Analysis ◽  
Solar Wind Entry

We present a coordinated observation with the Magnetospheric Multiscale (MMS) mission, located in the Earth’s magnetotail plasma sheet, and the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) mission, located in the solar wind, in order to understand the formation mechanism of the cold and dense plasma sheet (CDPS). MMS detected two CDPSs composed of two ion populations with different energies, where the energy of the cold ion population is the same as that of the solar wind measured by ARTEMIS. This feature directly indicates that the CDPSs are caused by the solar wind entry. In addition, He+ was observed in the CDPSs. The plasma density in these two CDPSs are ~1.8 cm−3 and ~10 cm−3, respectively, roughly 4–30 times the average value of a plasma sheet. We performed a cross-correlation analysis on the ion density of the CDPS and the solar wind, and we found that it takes 3.7–5.9 h for the solar wind to enter the plasma sheet. Such a coordinated observation confirms the previous speculation based on single-spacecraft measurements.

scholarly journals Geotail observations of temperature anisotropy of the two-component protons in the dusk plasma sheet

2007 ◽  
Vol 25 (3) ◽  
pp. 769-777 ◽  
Author(s):  
M. N. Nishino ◽  
M. Fujimoto ◽  
T. Terasawa ◽  
G. Ueno ◽  
K. Maezawa ◽  
...  
Keyword(s):  
Solar Wind ◽  
Plasma Sheet ◽  
Transport Process ◽  
Cold Plasma ◽  
Strong Anisotropy ◽  
Temperature Anisotropy ◽  
Low Latitude ◽  
Two Component ◽  
Cold Component

Abstract. In search for clues towards the understanding of the cold plasma sheet formation under northward IMF, we study the temperature anisotropy of the two-component protons in the plasma sheet near the dusk low-latitude boundary observed by the Geotail spacecraft. The two-component protons result from mixing of the cold component from the solar wind and the hot component of the magnetospheric origin, and may be the most eloquent evidence for the transport process across the magnetopause. The cold component occasionally has a strong anisotropy in the dusk flank, and the sense of the anisotropy depends on the observed locations: the parallel temperature is enhanced in the tail flank while the perpendicular temperature is enhanced on the dayside. The hot component is nearly isotropic in the tail while the perpendicular temperature is enhanced on the dayside. We discuss possible mechanism that can lead to the observed temperature anisotropies.

scholarly journals Correlation between ground-based observations of substorm signatures and magnetotail dynamics

2005 ◽  
Vol 23 (3) ◽  
pp. 997-1011 ◽  
Author(s):  
E. Borälv ◽  
H. J. Opgenoorth ◽  
K. Kauristie ◽  
M. Lester ◽  
J.-M. Bosqued ◽  
...  
Keyword(s):  
Solar Wind ◽  
Event Study ◽  
Plasma Sheet ◽  
Sheet Thickness ◽  
Substorm Onset ◽  
Boundary Motion ◽  
Thickness Variations ◽  
Magnetotail Dynamics

Abstract. We present a substorm event study using the four Cluster spacecraft in combination with ground-based instruments, in order to perform simultaneous observations in the ionosphere and magnetotail. We show good correlation between substorm signatures on the ground and in the magnetotail, even though data from the northern-ground and southern-tail hemispheres are compared. During this event ground-based magnetometers show a substorm onset over Scandinavia in the pre-midnight sector. Within 1.5h the onset and three intensifications are apparent in the magnetograms. For all the substorm signatures seen on the ground, corresponding plasma sheet boundary motion is visible at Cluster, located at a downtail distance of 18.5 RE. As a result of the substorm onset and intensifications, Cluster moves in and out between the southern plasma sheet and lobe. Due to the lack of an apparent solar wind driver and the good correlation between substorm signatures on the ground, we conclude the substorm itself is the driver for these plasma sheet dynamics. We show that in the scales of Cluster inter-spacecraft distances (~0.5 RE) the inferred plasma sheet motion is often directed in both Ygsm- and Zgsm-directions, and discuss this finding in the context of previous studies of tail flapping and plasma sheet thickness variations.

scholarly journals Anisotropy of the Taylor scale and the correlation scale in plasma sheet and solar wind magnetic field fluctuations

2009 ◽  
Vol 114 (A7) ◽  
pp. n/a-n/a ◽  
Author(s):  
James M. Weygand ◽  
W. H. Matthaeus ◽  
S. Dasso ◽  
M. G. Kivelson ◽  
L. M. Kistler ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Plasma Sheet ◽  
Solar Wind Magnetic Field ◽  
Field Fluctuations ◽  
Correlation Scale

The Earth's plasma sheet as a laboratory for flow turbulence in high-β MHD

1997 ◽  
Vol 57 (1) ◽  
pp. 1-34 ◽  
Author(s):  
JOSEPH E. BOROVSKY ◽  
RICHARD C. ELPHIC ◽  
HERBERT O. FUNSTEN ◽  
MICHELLE F. THOMSEN
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Plasma Sheet ◽  
Sheet Material ◽  
Single Point ◽  
Power Laws ◽  
Fluxgate Magnetometer ◽  
Flow Measurements ◽  
Field Fluctuations ◽  
Flow Velocities

The bulk flows and magnetic-field fluctuations of the plasma sheet are investigated using single-point measurements from the ISEE-2 Fast Plasma Experiment and fluxgate magnetometer. Ten several-hour-long intervals of continuous data (with 3 s and 12 s time resolution) are analysed. The plasma-sheet flow appears to be strongly ‘turbulent’ (i.e. the flow is dominated by fluctuations that are unpredictable, with rms velocities[Gt ]mean velocities and with field fluctuations≈mean fields). The flow velocities are typically sub-Alfvénic. The flow-velocity probability distribution P(v) is constructed, and is found to be well fitted by exponential functions. Autocorrelation functions [Ascr ](τ) are constructed, and the autocorrelation times τcorr for the flow velocities are found to be about 2 min. From the flow measurements, an estimate of the mixing length in the plasma sheet is produced, yielding Lmix≈2 Earth radii; correspondingly, the plasma-sheet material appears to be well mixed in density and temperature. An eddy viscosity for the plasma sheet is also estimated. Power spectra, which are constructed from the v(t) and B(t) time series, have portions that are power laws with spectral indices that are near the range of those expected for turbulence theories. The plasma sheet may provide a laboratory for the study of turbulence in parameter regimes different from that of solar-wind turbulence: the plasma sheet is a β[Gt ]1, hot-ion plasma, and the turbulence may be strongly driven rather than well developed. The turbulent nature of the flow and the disordered nature of the magnetic field have implications for the transport of plasma-sheet material, for the penetration of the solar-wind electric field into the plasma sheet, and for the calculation of particle orbits in the magnetotail.

Sign in / Sign up

Export Citation Format

Share Document