Are small-scale field-aligned currents and magneto sheath-like particle precipitation signatures of the same low-altitude cusp?

J. Watermann, P. Stauning, H. Luhr, P.T. Newell, Freddy Christiansen, K. Schlegel

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

We examined some 75 observations from the low-altitude Earth orbiting DMSP, Orsted and CHAMP satellites which were taken in the region of the nominal cusp. Our objective was to determine whether the actually observed cusp locations as inferred from magnetosheath-like particle precipitation ("particle cusp") and intense small-scale magnetic field variations ("current cusp"), respectively, were identical and were consistent with the statistically expected latitude of the cusp derived from a huge number of charged particle spectrograms ("statistical cusp"). The geocentric coordinates of the satellites were converted into AACGM coordinates, and the geomagnetic latitude of the cusp boundaries (as indicated by precipitating particles and small-scale field-aligned currents) set in relation to the IMF-B-z dependent latitude of the equatorward boundary of the statistical cusp. We find that the actually observed latitude of the particle cusp matches well the statistically expected latitude while the current cusp appears to cover most of the statistical cusp and also a approximate to 1 degrees wide section beyond the equatorward boundary of the statistical cusp. This leads us to suggest that intense small-scale field-aligned currents are generated in the cusp but also in the transition zone between the low-latitude boundary layer (LLBL) and the cusp, probably within both regimes, the cusp and the open LLBL. The small-scale field-aligned currents are possibly a consequence of turbulence and/or instabilities associated with the process of opening previously closed magnetospheric field lines and merging them with the interplanetary magnetic field.
Original languageEnglish
JournalAdvances in Space Research
Volume43
Issue number1
Pages (from-to)41-46
ISSN0273-1177
DOIs
Publication statusPublished - 2009

Keywords

  • Low-altitude cusp
  • Field-aligned currents
  • Charged particle precipitation
  • Polar ionosphere

Cite this

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title = "Are small-scale field-aligned currents and magneto sheath-like particle precipitation signatures of the same low-altitude cusp?",
abstract = "We examined some 75 observations from the low-altitude Earth orbiting DMSP, Orsted and CHAMP satellites which were taken in the region of the nominal cusp. Our objective was to determine whether the actually observed cusp locations as inferred from magnetosheath-like particle precipitation ({"}particle cusp{"}) and intense small-scale magnetic field variations ({"}current cusp{"}), respectively, were identical and were consistent with the statistically expected latitude of the cusp derived from a huge number of charged particle spectrograms ({"}statistical cusp{"}). The geocentric coordinates of the satellites were converted into AACGM coordinates, and the geomagnetic latitude of the cusp boundaries (as indicated by precipitating particles and small-scale field-aligned currents) set in relation to the IMF-B-z dependent latitude of the equatorward boundary of the statistical cusp. We find that the actually observed latitude of the particle cusp matches well the statistically expected latitude while the current cusp appears to cover most of the statistical cusp and also a approximate to 1 degrees wide section beyond the equatorward boundary of the statistical cusp. This leads us to suggest that intense small-scale field-aligned currents are generated in the cusp but also in the transition zone between the low-latitude boundary layer (LLBL) and the cusp, probably within both regimes, the cusp and the open LLBL. The small-scale field-aligned currents are possibly a consequence of turbulence and/or instabilities associated with the process of opening previously closed magnetospheric field lines and merging them with the interplanetary magnetic field.",
keywords = "Low-altitude cusp, Field-aligned currents, Charged particle precipitation, Polar ionosphere",
author = "J. Watermann and P. Stauning and H. Luhr and P.T. Newell and Freddy Christiansen and K. Schlegel",
year = "2009",
doi = "10.1016/j.asr.2008.03.031",
language = "English",
volume = "43",
pages = "41--46",
journal = "Advances in Space Research",
issn = "0273-1177",
publisher = "Pergamon Press",
number = "1",

}

Are small-scale field-aligned currents and magneto sheath-like particle precipitation signatures of the same low-altitude cusp? / Watermann, J.; Stauning, P.; Luhr, H.; Newell, P.T.; Christiansen, Freddy; Schlegel, K.

In: Advances in Space Research, Vol. 43, No. 1, 2009, p. 41-46.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Are small-scale field-aligned currents and magneto sheath-like particle precipitation signatures of the same low-altitude cusp?

AU - Watermann, J.

AU - Stauning, P.

AU - Luhr, H.

AU - Newell, P.T.

AU - Christiansen, Freddy

AU - Schlegel, K.

PY - 2009

Y1 - 2009

N2 - We examined some 75 observations from the low-altitude Earth orbiting DMSP, Orsted and CHAMP satellites which were taken in the region of the nominal cusp. Our objective was to determine whether the actually observed cusp locations as inferred from magnetosheath-like particle precipitation ("particle cusp") and intense small-scale magnetic field variations ("current cusp"), respectively, were identical and were consistent with the statistically expected latitude of the cusp derived from a huge number of charged particle spectrograms ("statistical cusp"). The geocentric coordinates of the satellites were converted into AACGM coordinates, and the geomagnetic latitude of the cusp boundaries (as indicated by precipitating particles and small-scale field-aligned currents) set in relation to the IMF-B-z dependent latitude of the equatorward boundary of the statistical cusp. We find that the actually observed latitude of the particle cusp matches well the statistically expected latitude while the current cusp appears to cover most of the statistical cusp and also a approximate to 1 degrees wide section beyond the equatorward boundary of the statistical cusp. This leads us to suggest that intense small-scale field-aligned currents are generated in the cusp but also in the transition zone between the low-latitude boundary layer (LLBL) and the cusp, probably within both regimes, the cusp and the open LLBL. The small-scale field-aligned currents are possibly a consequence of turbulence and/or instabilities associated with the process of opening previously closed magnetospheric field lines and merging them with the interplanetary magnetic field.

AB - We examined some 75 observations from the low-altitude Earth orbiting DMSP, Orsted and CHAMP satellites which were taken in the region of the nominal cusp. Our objective was to determine whether the actually observed cusp locations as inferred from magnetosheath-like particle precipitation ("particle cusp") and intense small-scale magnetic field variations ("current cusp"), respectively, were identical and were consistent with the statistically expected latitude of the cusp derived from a huge number of charged particle spectrograms ("statistical cusp"). The geocentric coordinates of the satellites were converted into AACGM coordinates, and the geomagnetic latitude of the cusp boundaries (as indicated by precipitating particles and small-scale field-aligned currents) set in relation to the IMF-B-z dependent latitude of the equatorward boundary of the statistical cusp. We find that the actually observed latitude of the particle cusp matches well the statistically expected latitude while the current cusp appears to cover most of the statistical cusp and also a approximate to 1 degrees wide section beyond the equatorward boundary of the statistical cusp. This leads us to suggest that intense small-scale field-aligned currents are generated in the cusp but also in the transition zone between the low-latitude boundary layer (LLBL) and the cusp, probably within both regimes, the cusp and the open LLBL. The small-scale field-aligned currents are possibly a consequence of turbulence and/or instabilities associated with the process of opening previously closed magnetospheric field lines and merging them with the interplanetary magnetic field.

KW - Low-altitude cusp

KW - Field-aligned currents

KW - Charged particle precipitation

KW - Polar ionosphere

U2 - 10.1016/j.asr.2008.03.031

DO - 10.1016/j.asr.2008.03.031

M3 - Journal article

VL - 43

SP - 41

EP - 46

JO - Advances in Space Research

JF - Advances in Space Research

SN - 0273-1177

IS - 1

ER -