scholarly journals Pi2 pulsations observed around the dawn terminator

2015 ◽  
Vol 120 (3) ◽  
pp. 2088-2098 ◽  
Author(s):  
S. Imajo ◽  
A. Yoshikawa ◽  
T. Uozumi ◽  
S. Ohtani ◽  
A. Nakamizo ◽  
...  
Keyword(s):  
Pi2 Pulsations

scholarly journals SABRE observations of Pi2 pulsations: case studies

1997 ◽  
Vol 15 (1) ◽  
pp. 40-53 ◽  
Author(s):  
E. G. Bradshaw ◽  
M. Lester
Keyword(s):  
Case Studies ◽  
Magnetic Activity ◽  
Auroral Zone ◽  
Field Of View ◽  
Ionospheric Currents ◽  
Pi2 Pulsation ◽  
First Case ◽  
Pi2 Pulsations ◽  
Generation Region

Abstract. The characteristics of substorm-associated Pi2 pulsations observed by the SABRE coherent radar system during three separate case studies are presented. The SABRE field of view is well positioned to observe the differences between the auroral zone pulsation signature and that observed at mid-latitudes. During the first case study the SABRE field of view is initially in the eastward electrojet, equatorward and to the west of the substorm-enhanced electrojet current. As the interval progresses, the western, upward field-aligned current of the substorm current wedge moves westward across the longitudes of the radar field of view. The westward motion of the wedge is apparent in the spatial and temporal signatures of the associated Pi2 pulsation spectra and polarisation sense. During the second case study, the complex field-aligned and ionospheric currents associated with the pulsation generation region move equatorward into the SABRE field of view and then poleward out of it again after the third pulsation in the series. The spectral content of the four pulsations during the interval indicate different auroral zone and mid-latitude signatures. The final case study is from a period of low magnetic activity when SABRE observes a Pi2 pulsation signature from regions equatorward of the enhanced substorm currents. There is an apparent mode change between the signature observed by SABRE in the ionosphere and that on the ground by magnetometers at latitudes slightly equatorward of the radar field of view. The observations are discussed in terms of published theories of the generation mechanisms for this type of pulsation. Different signatures are observed by SABRE depending on the level of magnetic activity and the position of the SABRE field of view relative to the pulsation generation region. A twin source model for Pi2 pulsation generation provides the clearest explanation of the signatures observed.

scholarly journals Effect of geomagnetic activity, solar wind and parameters of interplanetary magnetic field on regularities in intermittency of Pi2 geomagnetic pulsations

2015 ◽  
Vol 1 (3) ◽  
pp. 11-20 ◽  
Author(s):  
Надежда Куражковская ◽  
Nadezhda Kurazhkovskaya ◽  
Борис Клайн ◽  
Boris Klain
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Geomagnetic Activity ◽  
Dynamic Pressure ◽  
Cumulative Distribution ◽  
Qualitative Assessment ◽  
Geomagnetic Pulsations ◽  
Magnetospheric Substorms ◽  
Pi2 Pulsations

We present the results of investigation of the influence of geomagnetic activity, solar wind and parameters of the interplanetary magnetic field (IMF) on properties of the intermittency of midlatitude burst series of Pi2 geomagnetic pulsations observed during magnetospheric substorms on the nightside (substorm Pi2) and in the absence of these phenomena (nonsub-storm Pi2). We considered the index α as a main characteristic of intermittency of substorm and nonsubstorm Pi2 pulsations. The index α characterizes the slope of the cumulative distribution function of Pi2 burst amplitudes. The study indicated that the value and dynamics of the index α varies depending on the planetary geomagnetic activity, auroral activity and the intensity of magnetospheric ring currents. In addition, the forms of dependences of the index α on the density n, velocity V, dynamic pressure Pd of the solar wind and IMF Bx-component are different. The behavior of the index α depending on the module of B, By- and Bz-components is similar. We found some critical values of V, Pd, B, By- and Bz-components, after reaching of which the turbulence of the magnetotail plasma during substorm development is decreased. The revealed patterns of the intermittency of Pi2 pulsations can be used for qualitative assessment of turbulence level in the magnetotail plasma depending on changing interplanetary conditions.

scholarly journals Application of a global magnetospheric-ionospheric current model for dayside and terminator Pi2 pulsations

2017 ◽  
Vol 122 (8) ◽  
pp. 8589-8603 ◽  
Author(s):  
S. Imajo ◽  
A. Yoshikawa ◽  
T. Uozumi ◽  
Shin. Ohtani ◽  
A. Nakamizo ◽  
...  
Keyword(s):  
Current Model ◽  
Ionospheric Current ◽  
Pi2 Pulsations

CRRES electric field study of the radial mode structure of Pi2 pulsations

2003 ◽  
Vol 108 (A5) ◽  
Author(s):  
Kazue Takahashi ◽  
Dong-Hun Lee ◽  
Masahito Nosé ◽  
Roger R. Anderson ◽  
W. Jeffrey Hughes
Keyword(s):  
Electric Field ◽  
Field Study ◽  
Radial Mode ◽  
Mode Structure ◽  
Pi2 Pulsations

Properties and sources of low and very low latitude Pi2 pulsations

1998 ◽  
Vol 103 (A2) ◽  
pp. 2343-2358 ◽  
Author(s):  
Y. Li ◽  
B. J. Fraser ◽  
F. W. Menk ◽  
D. J. Webster ◽  
K. Yumoto
Keyword(s):  
Low Latitude ◽  
Pi2 Pulsations

A new method to calculate the time delay of the Pi2 pulsations

2016 ◽  
Vol 57 (2) ◽  
pp. 701-709 ◽  
Author(s):  
Essam Ghamry ◽  
Adel Fathy
Keyword(s):  
Time Delay ◽  
New Method ◽  
Pi2 Pulsations

scholarly journals EISCAT observations of unusual flows in the morning sector associated with weak substorm activity

1994 ◽  
Vol 12 (6) ◽  
pp. 541-553 ◽  
Author(s):  
N. J. Fox ◽  
M. Lockwood ◽  
S. W. H. Cowley ◽  
M. P. Freeman ◽  
E. Friis-Christensen ◽  
...  
Keyword(s):  
Auroral Oval ◽  
Geosynchronous Orbit ◽  
Polar Cap ◽  
Expansion Phase ◽  
Geomagnetic Tail ◽  
Density Depletion ◽  
Significant Difference ◽  
Pi2 Pulsations ◽  
Substorm Activity ◽  
Open Flux

Abstract. A discussion is given of plasma flows in the dawn and nightside high-latitude ionospheric regions during substorms occurring on a contracted auroral oval, as observed using the EISCAT CP-4-A experiment. Supporting data from the PACE radar, Greenland magnetometer chain, SAMNET magnetometers and geostationary satellites are compared to the EISCAT observations. On 4 October 1989 a weak substorm with initial expansion phase onset signatures at 0030 UT, resulted in the convection reversal boundary observed by EISCAT (at ~0415 MLT) contracting rapidly poleward, causing a band of elevated ionospheric ion temperatures and a localised plasma density depletion. This polar cap contraction event is shown to be associated with various substorm signatures; Pi2 pulsations at mid-latitudes, magnetic bays in the midnight sector and particle injections at geosynchronous orbit. A similar event was observed on the following day around 0230 UT (~0515 MLT) with the unusual and significant difference that two convection reversals were observed, both contracting poleward. We show that this feature is not an ionospheric signature of two active reconnection neutral lines as predicted by the near-Earth neutral model before the plasmoid is "pinched off", and present two alternative explanations in terms of (1) viscous and lobe circulation cells and (2) polar cap contraction during northward IMF. The voltage associated with the anti-sunward flow between the reversals reaches a maximum of 13 kV during the substorm expansion phase. This suggests it to be associated with the polar cap contraction and caused by the reconnection of open flux in the geomagnetic tail which has mimicked "viscous-like" momentum transfer across the magnetopause.

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