scholarly journals Observed relationships between electric fields and auroral particle precipitation

1973 ◽  
Vol 78 (1) ◽  
pp. 145-170 ◽  
Author(s):  
D. A. Gurnett ◽  
L. A. Frank
Keyword(s):  
Electric Fields ◽  
Particle Precipitation ◽  
Auroral Particle Precipitation

scholarly journals Strong sunward propagating flow bursts in the night sector during quiet solar wind conditions: SuperDARN and satellite observations

2002 ◽  
Vol 20 (6) ◽  
pp. 771-779 ◽  
Author(s):  
C. Senior ◽  
J.-C. Cerisier ◽  
F. Rich ◽  
M. Lester ◽  
G. K. Parks
Keyword(s):  
Convective Transport ◽  
High Time Resolution ◽  
Polar Cap ◽  
Particle Precipitation ◽  
Phase Velocities ◽  
Plasma Injection ◽  
Night Side ◽  
Magnetospheric Boundaries ◽  
Auroral Particle Precipitation ◽  
Imf Clock Angle

Abstract. High-time resolution data from the two Iceland SuperDARN HF radars show very strong nightside convection activity during a prolonged period of low geomagnetic activity and northward interplanetary magnetic field (IMF). Flows bursts with velocities ranging from 0.8 to 1.7 km/s are observed to propagate in the sunward direction with phase velocities up to 1.5 km/s. These bursts occur over several hours of MLT in the 20:00–01:00 MLT sector, in the evening-side sunward convection. Data from a simultaneous DMSP pass and POLAR UVI images show a very contracted polar cap and extended regions of auroral particle precipitation from the magnetospheric boundaries. A DMSP pass over the Iceland-West field-of-view while one of these sporadic bursts of enhanced flow is observed, indicates that the flow bursts appear within the plasma sheet and at its outward edge, which excludes Kelvin-Helmholtz instabilities at the magnetopause boundary as the generation mechanism. In the nightside region, the precipitation is more spot-like and the convection organizes itself as clockwise U-shaped structures. We interpret these flow bursts as the convective transport following plasma injection events from the tail into the night-side ionosphere. We show that during this period, where the IMF clock angle is around 70°, the dayside magnetosphere is not completely closed.Key words. Ionosphere (Auroral ionosphere; Ionospheremagnetosphere interactions; Particle precipitation)

scholarly journals Cosmic radio noise absorption events associated with equatorward drifting arcs during a substorm growth phase

2004 ◽  
Vol 22 (5) ◽  
pp. 1675-1686 ◽  
Author(s):  
J. R. T. Jussila ◽  
A. T. Aikio ◽  
S. Shalimov ◽  
S. R. Marple
Keyword(s):  
Electron Temperature ◽  
Electric Fields ◽  
Growth Phase ◽  
Energetic Electron ◽  
Cosmic Radio ◽  
Radio Noise ◽  
Particle Precipitation ◽  
Noise Absorption ◽  
D Region ◽  
E Region

Abstract. Cosmic radio noise absorption (CNA) events associated with equatorward drifting arcs during a substorm growth phase are studied by using simultaneous optical auroral, IRIS imaging riometer and EISCAT incoherent scatter radar measurements. The CNA is generally attributed to energetic particle precipitation in the D-region. However, it has been argued that plasma irregularities or enhanced electron temperature (Te) in the E-region could also produce CNA. Both of the latter mechanisms are related to intense electric fields in the ionosphere. We present two events which occur during a substorm growth phase in the evening MLT sector. In both of the events, an auroral arc is drifting equatorward, together with a region of CNA (auroral absorption bay) located on the equatorward side and outside of the arc. Both of the events are associated with enhanced D-region electron density on the equatorward side of the auroral arc, but in the second event, a region of intense electric field and enhanced electron temperature in the E-region is also located on the equatorward side of the arc. We show that in the studied events neither plasma instabilities nor enhanced Te play a significant role in producing the measured CNA, but the CNA in the vicinity of the equatorward drifting arcs is produced by D-region energetic electron precipitation. Key words. Ionosphere (auroral ionosphere; particle precipitation; electric fields and currents)

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 Radar detection of a localized 1.4 Hz pulsation in auroral plasma, simultaneous with pulsating optical emissions, during a substorm

2010 ◽  
Vol 28 (10) ◽  
pp. 1961-1979 ◽  
Author(s):  
R. Cosgrove ◽  
M. Nicolls ◽  
H. Dahlgren ◽  
S. Ranjan ◽  
E. Sanchez ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Optical Emission ◽  
Recovery Phase ◽  
Alfven Wave ◽  
Theoretical Argument ◽  
Particle Precipitation ◽  
Optical Emissions ◽  
Auroral Substorm ◽  
Central Result

Abstract. Many pulsating phenomena are associated with the auroral substorm. It has been considered that some of these phenomena involve kilometer-scale Alfvén waves coupling the magnetosphere and ionosphere. Electric field oscillations at the altitude of the ionosphere are a signature of such wave activity that could distinguish it from other sources of auroral particle precipitation, which may be simply tracers of magnetospheric activity. Therefore, a ground based diagnostic of kilometer-scale oscillating electric fields would be a valuable tool in the study of pulsations and the auroral substorm. In this study we attempt to develop such a tool in the Poker Flat incoherent scatter radar (PFISR). The central result is a statistically significant detection of a 1.4 Hz electric field oscillation associated with a similar oscillating optical emission, during the recovery phase of a substorm. The optical emissions also contain a bright, lower frequency (0.2 Hz) pulsation that does not show up in the radar backscatter. The fact that higher frequency oscillations are detected by the radar, whereas the bright, lower frequency optical pulsation is not detected by the radar, serves to strengthen a theoretical argument that the radar is sensitive to oscillating electric fields, but not to oscillating particle precipitation. Although it is difficult to make conclusions as to the physical mechanism, we do not find evidence for a plane-wave-like Alfvén wave; the detected structure is evident in only two of five adjacent beams. We emphasize that this is a new application for ISR, and that corroborating results are needed.

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