scholarly journals Effect of the orientation of interplanetary shock on the geomagnetic sudden commencement

2002 ◽  
Vol 107 (A12) ◽  
pp. SMP 6-1-SMP 6-10 ◽  
Author(s):  
T. Takeuchi ◽  
C. T. Russell ◽  
T. Araki
Keyword(s):  
Interplanetary Shock ◽  
Sudden Commencement ◽  
Geomagnetic Sudden Commencement

Automatic Detection of Geomagnetic Sudden Commencement Using Lifting Wavelet Filters

1999 ◽  
pp. 242-251 ◽  
Author(s):  
Shigeru Takano ◽  
Teruya Minamoto ◽  
Hiroki Arimura ◽  
Koichi Niijima ◽  
Toshihiko Iyemori ◽  
...  
Keyword(s):  
Automatic Detection ◽  
Sudden Commencement ◽  
Wavelet Filters ◽  
Lifting Wavelet ◽  
Geomagnetic Sudden Commencement

scholarly journals Observations of ionospheric flows and particle precipitation following a Sudden Commencement

2000 ◽  
Vol 18 (8) ◽  
pp. 908-917 ◽  
Author(s):  
E. Nielsen ◽  
F. Honary
Keyword(s):  
Electric Fields ◽  
Interplanetary Shock ◽  
Sudden Commencement ◽  
Interplanetary Shocks ◽  
Particle Precipitation ◽  
Flow Modulation ◽  
Interplanetary Physics ◽  
Flow Speeds ◽  
Wind Spacecraft ◽  
Electric Fields And Currents

Abstract. On May 4, 1998, at 0227 UT an interplanetary shock crossed the WIND spacecraft, and half an hour later a Sudden Commencement occurred. Coinciding with the Sudden Commencement a rapid intensification of the flux of particle precipitation into the ionosphere was observed. Evidence is presented that the ionospheric electric fields were influenced by the associated dynamic variations of the ionospheric conductivities. Following the initial phase the ionospheric flow speeds increased rapidly over the next 20 min to more than 2000 m/s, in agreement with an increased effective coupling of the solar wind energy to the magnetosphere following the interplanetary shock that caused the Sudden Commencement. These strong flows were meandering in latitude, a type of plasma flow modulation that has been reported before to occur during Omega band events: a string of alternating field-aligned currents propagating eastward. The riometer absorption was found to be at a minimum in regions associated with outward directed field aligned currents. The riometer absorption regions (the regions of particle precipitation) were drifting  with E × B drift speed of the ionospheric electrons.Key words: Interplanetary physics (interplanetary shocks) - Ionosphere (electric fields and currents) - Magnetospheric physics (energetic particles, precipitating)

scholarly journals Penetration of the electric fields of the geomagnetic sudden commencement over the globe as observed with the HF Doppler sounders and magnetometers

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Takashi Kikuchi ◽  
Jaroslav Chum ◽  
Ichiro Tomizawa ◽  
Kumiko K. Hashimoto ◽  
Keisuke Hosokawa ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Sudden Commencement ◽  
Ionospheric Currents ◽  
Republic Of China ◽  
F Region ◽  
Electric And Magnetic Fields ◽  
Magnetometer Data ◽  
Electric Potentials ◽  
Geomagnetic Sudden Commencement

AbstractUsing the HF Doppler sounders at middle and low latitudes (Prague, Czech Republic; Tucuman, Argentina; Zhongli, Republic of China, and Sugadaira, Japan), we observed the electric fields of the geomagnetic sudden commencement (SC) propagating near-instantaneously (within 10 s) over the globe. We found that the electric fields of the preliminary impulse (PI) and main impulse (MI) of the SC are in opposite direction to each other and that the PI and MI electric fields are directed from the dusk to dawn and dawn to dusk, respectively, manifesting the nature of the curl-free potential electric field. We further found that the onset and peak of the PI electric field are simultaneous on the day and nightsides (0545, 1250, 1345 MLT) within the resolution of 10 s. With the magnetometer data, we confirmed the near-instantaneous development of the ionospheric currents from high latitudes to the equator and estimated the location of the field-aligned currents that supply the ionospheric currents. The global simultaneity of the electric and magnetic fields does not require the contribution of the magnetohydrodynamic waves in the magnetosphere nor in the F-region ionosphere. The global simultaneity and day–night asymmetry of the electric fields are explained with the ionospheric electric potentials transmitted at the speed of light by the TM0 mode waves in the Earth-ionosphere waveguide.

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