Coordinated Cluster and ground-based instrument observations of transient changes in the magnetopause boundary layer during an interval of predominantly northward IMF: relation to reconnection pulses and FTE signatures
We study a series of transient entries into the low-latitude boundary layer (LLBL) of all four Cluster spacecraft during an outbound pass through the mid-afternoon magnetopause ( [ XGSM, YGSM, ZGSM ] ≈ [ 2, 7, 9 ] <i>R<sub>E</sub></i>). The events take place during a...
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
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| Language: | English |
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Copernicus Publications
2001-09-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/19/1613/2001/angeo-19-1613-2001.pdf |
| _version_ | 1831677243658600448 |
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| author | M. Lockwood M. Lockwood A. Fazakerley H. Opgenoorth J. Moen J. Moen A. P. van Eyken M. Dunlop J.-M. Bosqued G. Lu C. Cully P. Eglitis I. W. McCrea M. A. Hapgood M. N. Wild R. Stamper W. Denig M. Taylor J. A. Wild G. Provan O. Amm K. Kauristie T. Pulkkinen A. Strømme P. Prikryl F. Pitout A. Balogh H. Rème R. Behlke T. Hansen R. Greenwald H. Frey S. K. Morley D. Alcaydé P.-L. Blelly E. Donovan M. Engebretson M. Lester J. Watermann M. F. Marcucci |
| author_facet | M. Lockwood M. Lockwood A. Fazakerley H. Opgenoorth J. Moen J. Moen A. P. van Eyken M. Dunlop J.-M. Bosqued G. Lu C. Cully P. Eglitis I. W. McCrea M. A. Hapgood M. N. Wild R. Stamper W. Denig M. Taylor J. A. Wild G. Provan O. Amm K. Kauristie T. Pulkkinen A. Strømme P. Prikryl F. Pitout A. Balogh H. Rème R. Behlke T. Hansen R. Greenwald H. Frey S. K. Morley D. Alcaydé P.-L. Blelly E. Donovan M. Engebretson M. Lester J. Watermann M. F. Marcucci |
| author_sort | M. Lockwood |
| collection | DOAJ |
| description | We study a series of
transient entries into the low-latitude boundary layer (LLBL) of all four
Cluster spacecraft during an outbound pass through the mid-afternoon
magnetopause ( [ XGSM, YGSM, ZGSM ] ≈ [ 2, 7, 9 ] <i>R<sub>E</sub></i>).
The events take place during an interval of northward IMF, as seen in the data
from the ACE satellite and lagged by a propagation delay of 75 min that is
welldefined by two separate studies: (1) the magnetospheric variations prior to
the northward turning (Lockwood et al., 2001, this issue) and (2) the field
clock angle seen by Cluster after it had emerged into the magnetosheath (Opgenoorth
et al., 2001, this issue). With an additional lag of 16.5 min, the transient
LLBL events correlate well with swings of the IMF clock angle (in GSM) to near
90°. Most of this additional lag is explained by ground-based observations,
which reveal signatures of transient reconnection in the pre-noon sector that
then take 10–15 min to propagate eastward to 15 MLT, where they are observed
by Cluster. The eastward phase speed of these signatures agrees very well with
the motion deduced by the cross-correlation of the signatures seen on the four
Cluster spacecraft. The evidence that these events are reconnection pulses
includes: transient erosion of the noon 630 nm (cusp/cleft) aurora to lower
latitudes; transient and travelling enhancements of the flow into the polar
cap, imaged by the AMIE technique; and poleward-moving events moving into the
polar cap, seen by the EISCAT Svalbard Radar (ESR). A pass of the DMSP-F15
satellite reveals that the open field lines near noon have been opened for some
time: the more recently opened field lines were found closer to dusk where the
flow transient and the poleward-moving event intersected the satellite pass.
The events at Cluster have ion and electron characteristics predicted and
observed by Lockwood and Hapgood (1998) for a Flux Transfer Event (FTE), with
allowance for magnetospheric ion reflection at Alfvénic disturbances in the
magnetopause reconnection layer. Like FTEs, the events are about 1 <i>R<sub>E</sub></i><sub>
</sub>in their direction of motion and show a rise in the magnetic field
strength, but unlike FTEs, in general, they show no pressure excess in their
core and hence, no characteristic bipolar signature in the boundary-normal
component. However, most of the events were observed when the magnetic field
was southward, i.e. on the edge of the interior magnetic cusp, or when the
field was parallel to the magnetic equatorial plane. Only when the satellite
begins to emerge from the exterior boundary (when the field was northward), do
the events start to show a pressure excess in their core and the consequent
bipolar signature. We identify the events as the first observations of FTEs at
middle altitudes.<br><br><b>Key words. </b>Magnetospheric physics
(magnetopause, cusp and boundary layers; magnetosphere-ionosphere interactions;
solar wind-magnetosphere interactions) |
| first_indexed | 2024-12-20T04:39:03Z |
| format | Article |
| id | doaj.art-e5feba8796bc4cb4baca14f8a77b5717 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-20T04:39:03Z |
| publishDate | 2001-09-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-e5feba8796bc4cb4baca14f8a77b57172022-12-21T19:53:11ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762001-09-01191613164010.5194/angeo-19-1613-2001Coordinated Cluster and ground-based instrument observations of transient changes in the magnetopause boundary layer during an interval of predominantly northward IMF: relation to reconnection pulses and FTE signaturesM. Lockwood0M. Lockwood1A. Fazakerley2H. Opgenoorth3J. Moen4J. Moen5A. P. van Eyken6M. Dunlop7J.-M. Bosqued8G. Lu9C. Cully10P. Eglitis11I. W. McCrea12M. A. Hapgood13M. N. Wild14R. Stamper15W. Denig16M. Taylor17J. A. Wild18G. Provan19O. Amm20K. Kauristie21T. Pulkkinen22A. Strømme23P. Prikryl24F. Pitout25A. Balogh26H. Rème27R. Behlke28T. Hansen29R. Greenwald30H. Frey31S. K. Morley32D. Alcaydé33P.-L. Blelly34E. Donovan35M. Engebretson36M. Lester37J. Watermann38M. F. Marcucci39Department of Physics and Astronomy, Southampton University, Southampton, UKSolar Terrestrial Physics Division, Department of Space Science and Technology, Rutherford Appleton Laboratory, Oxfordshire, UKMullard Space Science Laboratory, Holmbury St. Mary, Surrey, UKIRF, Swedish Institute of Space Physics, Uppsala Division, SwedenAlso at Arctic Geophysics, University Courses on Svalbard, Longyearbyen, NorwayDepartment of Physics, University of Oslo, Blindern, Oslo, NorwayEISCAT Scientific Association, Longyearbyen, Svalbard, NorwayBlackett Laboratory, Imperial College, London, UKCESR, Centre d’Etude Spatiale des Rayonnements, Toulouse, FranceHigh Altitude Observatory, National Center for Atmospheric Research, Boulder, Colorado, USAUniversity of Calgary, Calgary, CanadaIRF, Swedish Institute of Space Physics, Uppsala Division, SwedenSolar Terrestrial Physics Division, Department of Space Science and Technology, Rutherford Appleton Laboratory, Oxfordshire, UKSolar Terrestrial Physics Division, Department of Space Science and Technology, Rutherford Appleton Laboratory, Oxfordshire, UKSolar Terrestrial Physics Division, Department of Space Science and Technology, Rutherford Appleton Laboratory, Oxfordshire, UKSolar Terrestrial Physics Division, Department of Space Science and Technology, Rutherford Appleton Laboratory, Oxfordshire, UKAFRL, Hanscom AFB, Cambridge, MA, USAMullard Space Science Laboratory, Holmbury St. Mary, Surrey, UKDepartment of Physics and Astonomy, Leicester University, Leicester, UKDepartment of Physics and Astonomy, Leicester University, Leicester, UKFinnish Meteorological Institute, Helsinki, FinlandFinnish Meteorological Institute, Helsinki, FinlandFinnish Meteorological Institute, Helsinki, FinlandUniversity of Tromsø, Tromsø, NorwayCommunications Research Centre, Ottawa, Ontario, CanadaIRF, Swedish Institute of Space Physics, Uppsala Division, SwedenBlackett Laboratory, Imperial College, London, UKCESR, Centre d’Etude Spatiale des Rayonnements, Toulouse, FranceIRF, Swedish Institute of Space Physics, Uppsala Division, SwedenUniversity of Tromsø, Tromsø, NorwayRemote Sensing Group, Applied Physics Laboratory, John Hopkins University, Laurel, MD, USASpace Science Centre, Berkeley, USADepartment of Physics and Astronomy, Southampton University, Southampton, UKCESR, Centre d’Etude Spatiale des Rayonnements, Toulouse, FranceCESR, Centre d’Etude Spatiale des Rayonnements, Toulouse, FranceUniversity of Calgary, Calgary, CanadaDepartment of Physics, Augsburg College, Minneapolis, MN, USADepartment of Physics and Astonomy, Leicester University, Leicester, UKDanish Meteorological Institute, Kobenhavn, DenmarkIstituto di Fisica dello Spazio Interplanetario – CNR, Rome, ItalyWe study a series of transient entries into the low-latitude boundary layer (LLBL) of all four Cluster spacecraft during an outbound pass through the mid-afternoon magnetopause ( [ XGSM, YGSM, ZGSM ] ≈ [ 2, 7, 9 ] <i>R<sub>E</sub></i>). The events take place during an interval of northward IMF, as seen in the data from the ACE satellite and lagged by a propagation delay of 75 min that is welldefined by two separate studies: (1) the magnetospheric variations prior to the northward turning (Lockwood et al., 2001, this issue) and (2) the field clock angle seen by Cluster after it had emerged into the magnetosheath (Opgenoorth et al., 2001, this issue). With an additional lag of 16.5 min, the transient LLBL events correlate well with swings of the IMF clock angle (in GSM) to near 90°. Most of this additional lag is explained by ground-based observations, which reveal signatures of transient reconnection in the pre-noon sector that then take 10–15 min to propagate eastward to 15 MLT, where they are observed by Cluster. The eastward phase speed of these signatures agrees very well with the motion deduced by the cross-correlation of the signatures seen on the four Cluster spacecraft. The evidence that these events are reconnection pulses includes: transient erosion of the noon 630 nm (cusp/cleft) aurora to lower latitudes; transient and travelling enhancements of the flow into the polar cap, imaged by the AMIE technique; and poleward-moving events moving into the polar cap, seen by the EISCAT Svalbard Radar (ESR). A pass of the DMSP-F15 satellite reveals that the open field lines near noon have been opened for some time: the more recently opened field lines were found closer to dusk where the flow transient and the poleward-moving event intersected the satellite pass. The events at Cluster have ion and electron characteristics predicted and observed by Lockwood and Hapgood (1998) for a Flux Transfer Event (FTE), with allowance for magnetospheric ion reflection at Alfvénic disturbances in the magnetopause reconnection layer. Like FTEs, the events are about 1 <i>R<sub>E</sub></i><sub> </sub>in their direction of motion and show a rise in the magnetic field strength, but unlike FTEs, in general, they show no pressure excess in their core and hence, no characteristic bipolar signature in the boundary-normal component. However, most of the events were observed when the magnetic field was southward, i.e. on the edge of the interior magnetic cusp, or when the field was parallel to the magnetic equatorial plane. Only when the satellite begins to emerge from the exterior boundary (when the field was northward), do the events start to show a pressure excess in their core and the consequent bipolar signature. We identify the events as the first observations of FTEs at middle altitudes.<br><br><b>Key words. </b>Magnetospheric physics (magnetopause, cusp and boundary layers; magnetosphere-ionosphere interactions; solar wind-magnetosphere interactions)https://www.ann-geophys.net/19/1613/2001/angeo-19-1613-2001.pdf |
| spellingShingle | M. Lockwood M. Lockwood A. Fazakerley H. Opgenoorth J. Moen J. Moen A. P. van Eyken M. Dunlop J.-M. Bosqued G. Lu C. Cully P. Eglitis I. W. McCrea M. A. Hapgood M. N. Wild R. Stamper W. Denig M. Taylor J. A. Wild G. Provan O. Amm K. Kauristie T. Pulkkinen A. Strømme P. Prikryl F. Pitout A. Balogh H. Rème R. Behlke T. Hansen R. Greenwald H. Frey S. K. Morley D. Alcaydé P.-L. Blelly E. Donovan M. Engebretson M. Lester J. Watermann M. F. Marcucci Coordinated Cluster and ground-based instrument observations of transient changes in the magnetopause boundary layer during an interval of predominantly northward IMF: relation to reconnection pulses and FTE signatures Annales Geophysicae |
| title | Coordinated Cluster and ground-based instrument observations of transient changes in the magnetopause boundary layer during an interval of predominantly northward IMF: relation to reconnection pulses and FTE signatures |
| title_full | Coordinated Cluster and ground-based instrument observations of transient changes in the magnetopause boundary layer during an interval of predominantly northward IMF: relation to reconnection pulses and FTE signatures |
| title_fullStr | Coordinated Cluster and ground-based instrument observations of transient changes in the magnetopause boundary layer during an interval of predominantly northward IMF: relation to reconnection pulses and FTE signatures |
| title_full_unstemmed | Coordinated Cluster and ground-based instrument observations of transient changes in the magnetopause boundary layer during an interval of predominantly northward IMF: relation to reconnection pulses and FTE signatures |
| title_short | Coordinated Cluster and ground-based instrument observations of transient changes in the magnetopause boundary layer during an interval of predominantly northward IMF: relation to reconnection pulses and FTE signatures |
| title_sort | coordinated cluster and ground based instrument observations of transient changes in the magnetopause boundary layer during an interval of predominantly northward imf relation to reconnection pulses and fte signatures |
| url | https://www.ann-geophys.net/19/1613/2001/angeo-19-1613-2001.pdf |
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