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Monograph available for loan

Satellite measurements of Birkeland currents. Birkeland's work with geomagnetic disturbances in relation to modern research - pioneering study of magnetic storm phenomena (1989)

Potemra, T. A. ; Fukushima, Naosihi

Oslo : The Norwegian Museum of Science and Technology

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Call number: M 91.0577

In: The Kristian Birkeland Lecture

Type of Medium: Monograph available for loan

Pages: 43 S. : Ill.

Series Statement: The Kristian Birkeland Lecture

Language: English

Location: Upper compact magazine

Branch Library: GFZ Library

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2

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The dynamic cusp at low altitudes: a case study utilizing Viking, DMSP-F7, and Sondrestrom incoherent scatter radar observations (1994)

Watermann, J. ; Beaujardière, O. ; Lummerzheim, D. ; [et al.]

Springer

Annales geophysicae 12 (1994), S. 1144-1157

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ISSN: 0992-7689

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Abstract Coincident multi-instrument magnetospheric and ionospheric observations have made it possible to determine the position of the ionospheric footprint of the magnetospheric cusp and to monitor its evolution over time. The data used include charged particle and magnetic field measurements from the Earth-orbiting Viking and DMSP-F7 satellites, electric field measurements from Viking, interplanetary magnetic field and plasma data from IMP-8, and Sondrestrom incoherent scatter radar observations of the ionospheric plasma density, temperature, and convection. Viking detected cusp precipitation poleward of 75.5○ invariant latitude. The ionospheric response to the observed electron precipitation was simulated using an auroral model. It predicts enhanced plasma density and elevated electron temperature in the upper E- and F-regions. Sondrestrom radar observations are in agreement with the predictions. The radar detected a cusp signature on each of five consecutive antenna elevation scans covering 1.2 h local time. The cusp appeared to be about 2○ invariant latitude wide, and its ionospheric footprint shifted equatorward by nearly 2○ during this time, possibly influenced by an overall decrease in the IMF Bz component. The radar plasma drift data and the Viking magnetic and electric field data suggest that the cusp was associated with a continuous, rather than a patchy, merging between the IMF and the geomagnetic field.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s00585-994-1144-7

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3

Electronic Resource

Boundary determinations from low frequency magnetic field measurements (1994)

Zanetti, L. J. ; Potemra, T. A. ; Anderson, B. J.

Springer

Earth, moon and planets 67 (1994), S. 175-178

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ISSN: 1573-0794

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00613301

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4

Electronic Resource

Observation of Birkeland currents with the TRIAD satellite (1978)

Potemra, T. A.

Springer

Astrophysics and space science 58 (1978), S. 207-226

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ISSN: 1572-946X

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract The intimate connection between geomagnetic storms and the aurora was appreciated by many early scientists including Edmund Halley and Anders Celsius, but the first serious study of this phenomena was made by Kristian Birkeland who, during his polar expeditions of 1902–1903, determined that large-scale ionospheric current were associated with the aurora. Birkeland was also the first to suggest that these currents originated far from the Earth and that they flowed into and away from the polar atmosphere along the geomagnetic field lines. The existence of such field-aligned orBirkeland currents was widely disputed because it was not possible to unambiguously identify current systems that are field-aligned (Alfvén, 1939, 1940) and those which are completely contained in the ionosphere (Vestine and Chapman, 1938) only from a study of surface magnetic field measurements. During the last decade, the presence of Birkeland currents has been absolutely confirmed with particle and magnetic field observations acquired from a variety of rocket and satellite instruments. The vector magnetometer on the low-altitude (∼800 km) polar orbiting TRIAD satellite has been used to determine for the first time the flow direction, spatial distribution, and intensities of Birkeland currents in the north and south auroral regions. These observations support the mechanism originally proposed by Alfvén (1939, 1940)-later expanded by Shieldet al. (1969)-to drive Birkeland currents in the auroral regions, and they demonstrate the important role that these intense currents (ranging between 106 and 107 amperes) play in the coupling of energy between the magnetosphere and the lower ionosphere and atmosphere.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00645387

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5

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Near Magnetic Field Investigation, Instrumentation, Spacecraft Magnetics and Data Access (1997)

Lohr, D. A. ; Zanetti, L. J. ; Anderson, B. J. ; [et al.]

Springer

Space science reviews 82 (1997), S. 255-281

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ISSN: 1572-9672

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract The primary objective of the investigation is the search for a body-wide magnetic field of the near Earth asteroid Eros. The Near Earth Asteroid Rendezvous (NEAR) 3-axis fluxgate magnetometer includes a sensor mounted on the high-gain antenna feed structure. The NEAR Magnetic Facility Instrument (MFI) is a joint hardware effort between GSFC and APL. The design and magnetics approach achieved by the NEAR MFI effort entailed low-cost, up-front attention to engineering solutions which did not impact the schedule. The goal of the magnetometer is reliable magnetic field measurements within 5 nT, which necessitates the use of an extensive spacecraft magnetic interference model but is achievable with the full year's orbital data set. Such a goal has been shown viable with recent in-flight calibration data and comparisons to the WIND magnetometer data. The NEAR MFI effort has succeeded in providing magnetic field measurements for the first flight in NASA's Discovery line.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1005089829882

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Observations of low-energy electrons from AE-C in the south polar cusp during the geomagnetic storm of September 21, 1977 (1978)

Potemra, T. A. ; Bostrom, C. O. ; Doering, J. P. ; [et al.]

Springer

Space science reviews 22 (1978), S. 659-666

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ISSN: 1572-9672

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract The AE-C spacecraft skimmed through the southern polar cusp at a 400 km altitude during a large geomagnetic storm on September 21, 1977. This period has been designated as a special IMS period, and the AE-C data were acquired close to the times that data were acquired by the DMSP satellite at nearly the same location over the southern polar cap, and by the GEOS satellite located near the noon-meridian in the northern hemisphere. Low energy electrons (1-500 eV) were measured with the photoelectron spectrometer experiment experiment onboard AE-C. This instrument was operated in the mode which measured precipitating electron fluxes and backscattered electron fluxes in alternating 4s intervals with two sensors. A region of intense precipitating electron fluxes was observed near 0924 UT on September 21, 1977 extending from 69 degree invariant latitude at 1100 MLT to 72 degree invariant latitude at 1152 MLT. From the spectra of the precipitating electrons, this region is identified as the southern polar cusp. Since the K p equals 7- during this time, the displacement of the cusp down to these low latitudes is not unreasonable. Particle data obtained from the DMSP satellite on orbits close to AE-C, confirm that the position of the cusp was rapidly changing during this period, and was displaced to latitudes equatorward of the quiet time position. A second region of intense fluxes of precipitating electron was observed by AE-C at approximately 0933 UT from 69 degree invariant latitude near 1700 MLT to 66 degree invariant latitude near 1730 MLT. This region of low energy electron fluxes is characterized by slightly harder energy spectra and is interpreted as being the afternoon auroral zone. The remarkable and fortunate location of the AE-C, DMSP, and GEOS spacecraft during this special IMS period will allow future correlative studies aimed at the determination of the shape of the magnetosphere during very disturbed conditions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00223947

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Birkeland currents in the Earth's magnetosphere (1988)

Potemra, T. A.

Springer

Astrophysics and space science 144 (1988), S. 155-169

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ISSN: 1572-946X

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract As a result of his polar expeditions at the beginning of this century, Kristian Birkeland determined that intense ionospheric currents were associated with the aurora. Birkeland suggested that these currents originated far from the Earth and that they flowed ointo and away from the polar atmosphere along the geomagnetic field lines. The existence of such field-aligned or ‘Birkeland’ currents was disputed because it was not possible to unambiguously identify current systems that are field-aligned (as suggested by Alfvén, 1939, 1940) and those which are completely contained in the ionosphere (as developed by Vestine and Chapman, 1938) with surface magnetic field observations. The presence of Birkeland currents has been absolutely confirmed with satellite-borne particle and magnetic field experiments conducted over the past two decades. These satellite observations have determined the large-scale patterns, flow directions, and intensities of Birkeland currents in the auroral and polar regions, and their relationship to the orientation and magnitude of the interplanetary magnetic field. The Birkeland currents are directly associated with visible and UV auroral forms observed with satellites. The results obtained from a variety of recently launched satellites are discussed here. These include Sweden's first satellite, VIKING, which has provided evidence for resonant Alfvén waves on the same geomagnetic field lines that guide stationary Birkeland currents. These observations demonstrate the important role that these currents play in the coupling of energy between the interplanetary medium and the lower ionosphere and atmosphere.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00793179

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