Plasma structure within poleward-moving cusp/cleft auroral transients: EISCAT Svalbard radar observations and an explanation in terms of large local time extent of events
We report high-resolution observations of the southward-IMF cusp/cleft ionosphere made on December 16th 1998 by the EISCAT (European incoherent scatter) Svalbard radar (ESR), and compare them with observations of dayside auroral luminosity, as seen at a wavelength of 630 nm by a meridian scannin...
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2000-09-01
|
| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/18/1027/2000/angeo-18-1027-2000.pdf |
| _version_ | 1828345738252255232 |
|---|---|
| author | M. Lockwood M. Lockwood M. Lockwood M. Lockwood I. W. McCrea S. E. Milan J. Moen J. C. Cerisier A. Thorolfsson A. Thorolfsson |
| author_facet | M. Lockwood M. Lockwood M. Lockwood M. Lockwood I. W. McCrea S. E. Milan J. Moen J. C. Cerisier A. Thorolfsson A. Thorolfsson |
| author_sort | M. Lockwood |
| collection | DOAJ |
| description | We report high-resolution observations of the
southward-IMF cusp/cleft ionosphere made on December 16th 1998 by the EISCAT
(European incoherent scatter) Svalbard radar (ESR), and compare them with
observations of dayside auroral luminosity, as seen at a wavelength of 630 nm by
a meridian scanning photometer at Ny Ålesund, and of plasma flows, as seen by
the CUTLASS (co-operative UK twin location auroral sounding system) Finland HF
radar. The optical data reveal a series of poleward-moving transient red-line
(630 nm) enhancements, events that have been associated with bursts in the rate
of magnetopause reconnection generating new open flux. The combined observations
at this time have strong similarities to predictions of the effects of soft
electron precipitation modulated by pulsed reconnection, as made by Davis and
Lockwood (1996); however, the effects of rapid zonal flow in the ionosphere,
caused by the magnetic curvature force on the newly opened field lines, are
found to be a significant additional factor. In particular, it is shown how
enhanced plasma loss rates induced by the rapid convection can explain two
outstanding anomalies of the 630 nm transients, namely how minima in luminosity
form between the poleward-moving events and how events can re-brighten as they
move poleward. The observations show how cusp/cleft aurora and transient
poleward-moving auroral forms appear in the ESR data and the conditions which
cause enhanced 630 nm emission in the transients: they are an important first
step in enabling the ESR to identify these features away from the winter
solstice when supporting auroral observations are not available.<br><br><b>Key words: </b>Ionosphere (polar ionosphere) -
Magnetospheric physics (magnetopause; cusp and boundary layers; solar
wind-magnetosphere interactions) |
| first_indexed | 2024-04-14T00:16:39Z |
| format | Article |
| id | doaj.art-0a7e80afde32499d8c138b9fcba86452 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-04-14T00:16:39Z |
| publishDate | 2000-09-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-0a7e80afde32499d8c138b9fcba864522022-12-22T02:23:06ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762000-09-01181027104210.1007/s00585-000-1027-5Plasma structure within poleward-moving cusp/cleft auroral transients: EISCAT Svalbard radar observations and an explanation in terms of large local time extent of eventsM. Lockwood0M. Lockwood1M. Lockwood2M. Lockwood3I. W. McCrea4S. E. Milan5J. Moen6J. C. Cerisier7A. Thorolfsson8A. Thorolfsson9Space Science Department, Rutherford Appleton Laboratory, UKDepartment of Physics and Astronomy, Southampton University, UK<i>Correspondence to:</i> M. Lockwoode-mail: m.lockwood@rl.ac.ukSpace Science Department, Rutherford Appleton Laboratory, UKDepartment of Physics and Astronomy, Leicester University, UKArctic Geophysics, University Courses on Svalbard, Longyearben, NorwayCETP, 4, avenue Neptune, F-94107 Saint-Maur, CEDEX FranceCETP, 4, avenue Neptune, F-94107 Saint-Maur, CEDEX FranceScience Institute, Dunhaga 3, 107 Reykjavik, IcelandWe report high-resolution observations of the southward-IMF cusp/cleft ionosphere made on December 16th 1998 by the EISCAT (European incoherent scatter) Svalbard radar (ESR), and compare them with observations of dayside auroral luminosity, as seen at a wavelength of 630 nm by a meridian scanning photometer at Ny Ålesund, and of plasma flows, as seen by the CUTLASS (co-operative UK twin location auroral sounding system) Finland HF radar. The optical data reveal a series of poleward-moving transient red-line (630 nm) enhancements, events that have been associated with bursts in the rate of magnetopause reconnection generating new open flux. The combined observations at this time have strong similarities to predictions of the effects of soft electron precipitation modulated by pulsed reconnection, as made by Davis and Lockwood (1996); however, the effects of rapid zonal flow in the ionosphere, caused by the magnetic curvature force on the newly opened field lines, are found to be a significant additional factor. In particular, it is shown how enhanced plasma loss rates induced by the rapid convection can explain two outstanding anomalies of the 630 nm transients, namely how minima in luminosity form between the poleward-moving events and how events can re-brighten as they move poleward. The observations show how cusp/cleft aurora and transient poleward-moving auroral forms appear in the ESR data and the conditions which cause enhanced 630 nm emission in the transients: they are an important first step in enabling the ESR to identify these features away from the winter solstice when supporting auroral observations are not available.<br><br><b>Key words: </b>Ionosphere (polar ionosphere) - Magnetospheric physics (magnetopause; cusp and boundary layers; solar wind-magnetosphere interactions)https://www.ann-geophys.net/18/1027/2000/angeo-18-1027-2000.pdf |
| spellingShingle | M. Lockwood M. Lockwood M. Lockwood M. Lockwood I. W. McCrea S. E. Milan J. Moen J. C. Cerisier A. Thorolfsson A. Thorolfsson Plasma structure within poleward-moving cusp/cleft auroral transients: EISCAT Svalbard radar observations and an explanation in terms of large local time extent of events Annales Geophysicae |
| title | Plasma structure within poleward-moving cusp/cleft auroral transients: EISCAT Svalbard radar observations and an explanation in terms of large local time extent of events |
| title_full | Plasma structure within poleward-moving cusp/cleft auroral transients: EISCAT Svalbard radar observations and an explanation in terms of large local time extent of events |
| title_fullStr | Plasma structure within poleward-moving cusp/cleft auroral transients: EISCAT Svalbard radar observations and an explanation in terms of large local time extent of events |
| title_full_unstemmed | Plasma structure within poleward-moving cusp/cleft auroral transients: EISCAT Svalbard radar observations and an explanation in terms of large local time extent of events |
| title_short | Plasma structure within poleward-moving cusp/cleft auroral transients: EISCAT Svalbard radar observations and an explanation in terms of large local time extent of events |
| title_sort | plasma structure within poleward moving cusp cleft auroral transients eiscat svalbard radar observations and an explanation in terms of large local time extent of events |
| url | https://www.ann-geophys.net/18/1027/2000/angeo-18-1027-2000.pdf |
| work_keys_str_mv | AT mlockwood plasmastructurewithinpolewardmovingcuspcleftauroraltransientseiscatsvalbardradarobservationsandanexplanationintermsoflargelocaltimeextentofevents AT mlockwood plasmastructurewithinpolewardmovingcuspcleftauroraltransientseiscatsvalbardradarobservationsandanexplanationintermsoflargelocaltimeextentofevents AT mlockwood plasmastructurewithinpolewardmovingcuspcleftauroraltransientseiscatsvalbardradarobservationsandanexplanationintermsoflargelocaltimeextentofevents AT mlockwood plasmastructurewithinpolewardmovingcuspcleftauroraltransientseiscatsvalbardradarobservationsandanexplanationintermsoflargelocaltimeextentofevents AT iwmccrea plasmastructurewithinpolewardmovingcuspcleftauroraltransientseiscatsvalbardradarobservationsandanexplanationintermsoflargelocaltimeextentofevents AT semilan plasmastructurewithinpolewardmovingcuspcleftauroraltransientseiscatsvalbardradarobservationsandanexplanationintermsoflargelocaltimeextentofevents AT jmoen plasmastructurewithinpolewardmovingcuspcleftauroraltransientseiscatsvalbardradarobservationsandanexplanationintermsoflargelocaltimeextentofevents AT jccerisier plasmastructurewithinpolewardmovingcuspcleftauroraltransientseiscatsvalbardradarobservationsandanexplanationintermsoflargelocaltimeextentofevents AT athorolfsson plasmastructurewithinpolewardmovingcuspcleftauroraltransientseiscatsvalbardradarobservationsandanexplanationintermsoflargelocaltimeextentofevents AT athorolfsson plasmastructurewithinpolewardmovingcuspcleftauroraltransientseiscatsvalbardradarobservationsandanexplanationintermsoflargelocaltimeextentofevents |