| 1. |
- ELPHINSTONE, RD, et al.
(författare)
-
OBSERVATIONS IN THE VICINITY OF SUBSTORM ONSET - IMPLICATIONS FOR THE SUBSTORM PROCESS
- 1995
-
Ingår i: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS. - : AMER GEOPHYSICAL UNION. - 0148-0227. ; 100:A5, s. 7937-7969
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Multi-instrument data sets from the ground and satellites at both low and high altitude have provided new results concerning substorm onset and its source region in the magnetosphere. Twenty-six out of 37 substorm onset events showed evidence of azimuthal
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Ohtani, S, et al.
(författare)
-
4 Large-scale field-aligned current systems in the dayside high-latitude region
- 1995
-
Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 100, s. 137-153
-
Tidskriftsartikel (refereegranskat)abstract
- A system of four current sheets of large-scale field-aligned currents (FACs) was discovered in the data set of simultaneous Viking and DMSP-F7 crossings of the dayside high-latitude region. This paper reports four examples of this system that were observed in the prenoon sector. The flow polarities of FACs are upward, downward, upward, and downward, from equatorward to poleward. The lowest-latitude upward current is flowing mostly in the CPS precipitation region, often overlapping with the BPS at its poleward edge, and is interpreted as a region 2 current. The pair of downward and upward FACs in the middle of the structure are collocated with structured electron precipitation. The precipitation of high-energy (>1 keV) electrons is more intense in the lower-latitude downward current sheet. The highest-latitude downward flowing current sheet is located in a weak, low-energy particle precipitation region, suggesting that this current is flowing on open field lines. Simultaneous observations in the postnoon local time sector reveal the standard three-sheet structure of FACs, sometimes described as region 2, region 1, and mantle (referred to the midday region 0) currents. A high correlation was found between the occurrence of the four FAC sheet structure and negative interplanetary magnetic field (IMF) B-Y, We discuss the FAC structure in terms of three types of convection cells: the merging, viscous, and lobe cells. During strongly negative IMF B-Y two convection reversals exist in the prenoon sector; one is inside the viscous cell, and the other is between the viscous cell and the lobe cell. This structure of convection flow is supported by the Viking electric field and auroral UV image data. Based on the convection pattern, the four FAC sheet structure is interpreted as the latitudinal overlap of midday and morning FAC systems. We suggest that the four-current sheet structure is common in a certain prenoon local time sector during strongly negative IMF B-Y.
|
|
| 6. |
|
|
| 7. |
- VOGELSANG, H, et al.
(författare)
-
An ionospheric travelling convection vortex event observed by ground‐based magnetometers and by Viking
- 1993
-
Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 20:21, s. 2343-2346
-
Tidskriftsartikel (refereegranskat)abstract
- A transient ionospheric travelling convection vortex (ITCV) event was recorded by the EISCAT magnetometer cross in northern Scandinavia on April 21, 1986 around 8:40 MLT. Simultaneously, the near-conjugate satellite VIKING observed strong magnetic and electric field variations on closed magnetic field lines. The signatures seen by the spacecraft are consistent with a passage through two oppositely directed field-aligned current tubes. The total upward and downward currents turned out to be matched within a region of approximately 1000 km in the ionosphere. Because of the close spatial and temporal proximity of both observations we interpret the field-aligned currents as being associated with the ITCV. This is the first time that in-situ measurements of the currents connecting the ITCV to the source region close to the magnetopause have been published. Both the current density and the dimensions of the current tubes could be estimated here.
|
|
