Auroral torch structures: results of optical observations

doi:10.1016/0021-9169(93)90144-N

Journal of Atmospheric and Terrestrial Physics

Volume 55, Issue 14, December 1993, Pages 1775-1787

Journal of Atmospher...

https://doi.org/10.1016/0021-9169(93)90144-N Get rights and content

Abstract

Auroral torch structures are frequently observed as large scale wave-like undulations on the poleward edge of the diffuse precipitation zone. Their eastward drift velocity has the same order of magnitude and direction as the electric drift velocity usually observed in the morning sector. From a study of all-sky camera and TV data, the main peculiarities of the torch structures are shown. Three cases were studied. Height distributions of luminosity along the boundaries of the torch were made using the triangulation method in the first case. It was shown that the poleward boundary of the torch had the lowest altitudes around the crest. The second case was the appearance of a train consisting of five torches that existed for a relatively long time (~20 min), drifting eastward. On the contrary the last case was the successive development of two torches recorded by the TV camera. For the two latter cases the field-aligned mapping of the torches into the magnetotail is made using the latest version of the Tsyganenko magnetic field model (1989). The results of mapping showed that the generation of torch structures takes place quite close to the Earth, at a distance of 5–6 R_E.

References (27)

K.U. Kaila
An iterative method for calculating the altitudes and position of auroras along the arc
Planet. Space Sci.
(1987)
H.E.J. Koskinen et al.
Mapping of the auroral horn into magnetotail
Planet. Space Sci.
(1990)
G. Rajaram et al.
Wave characteristics of Ps6 magnetic variations and their implications for convective flow in magnetosphere
Planet. Space Sci.
(1986)
M.H. Rees
Auroral ionization and excitation by incident energetic electrons
Planet. Space Sci.
(1963)
A. Steen et al.
High time-resolution imaging of auroral arc deformation at substorm onset
Planet. Space Sci.
(1988)
A. Steen et al.
On the development of folds in auroral arcs
J. atmos. terr. Phys.
(1988)
N.A. Tsyganenko
A magnetospheric magneic field model with warped tail current sheet
Planet. Space Sci.
(1989)
S.-I. Akasofu
A study of auroral displays photographed from the DMSP-2 satellite and from Alaska meridian chain of stations
Space Sci. Rev.
(1974)
D. Andre et al.
Joint two-dimensional of ground magnetic and ionospheric electric currents associated with auroral currents, 5. Current system associated with eastward drifting omega bands
J. Geophys.
(1982)
W. Baumjohann
Spatially inhomogeneous current configurations as seen by the Scandinavian Magnetometer Array

G. Gustafsson et al.

Multi-method observations and modeling of the three dimensional current associated with a very strong Ps6 event

J. Geophys.

(1981)

K.U. Kaila

Three-dimensional mapping of the aurora from digitized all-sky pictures

K. Kawasaki et al.

Perturbation magnetic fields and current systems associated with eastward drifting auroral structures

J. geophys. Res.

(1979)

Cited by (13)

Automatic classification of mesoscale auroral forms using convolutional neural networks
2022, Journal of Atmospheric and Solar-Terrestrial Physics
Convolutional neural networks (CNNs) in deep learning enable the extraction of features in image data. Through the multi-layer superposition of a convolutional neural network, we can better capture the essential characteristics of different auroral subclasses and further classify auroral images in detail. Because the auroral morphological features often present abstract characteristics, our study compares different CNN architectures and different layering in order to test the best neural network model for mesoscale aurora classification. Although the classification models and subclasses used by us are both more complex, the highest F1 score of aurora classification of the test set reaches 99.6% (ResNet-50), which performs best comparing with previous works. Our classification models work also quite well when applied to an independent auroral image sequence, declaring our approach can automatically select images of various mesoscale auroral forms using CNNs, and allow the time sequence of auroral evolution to be seen automatically through the mesoscale auroral feature recognitions.
An interpretation of spacecraft and ground based observations of multiple omega band events
2015, Journal of Atmospheric and Solar-Terrestrial Physics
Citation Excerpt :
In general, the brightest edges of the omega bands lie near the interface between the region 1 and region 2 current system in the morning sector. A number of studies have used magnetic field models to identify the magnetospheric equatorial location of the observed omega bands mapped along field lines (Pulkkinen et al., 1991; Tagirov, 1993; and Wild et al., 2011). Pulkkinen et al. (1991) determined that the omega bands observed on March 25, 1986 mapped to 6–13 RE with Tsyganenko (1989) (T89) magnetic field model (Tsyganenko, 1989) and Tagirov (1993) found that the omega bands observed on April 9–10, 1986 mapped to 5–6 RE, also using the T89 model.
The source of the auroral phenomenon known as omega bands is not yet known. We examine in detail five different intervals when omega bands were observed on March 9th, 2008 between 0400 UT and 1100 UT over central Canada using both ground and space-based instrumentation. The THEMIS all sky imagers show the development of some of the omega bands from north–south streamers. Spherical elementary currents derived from ground magnetometer data indicate that the omega bands lie near the interface between the region 1 and region 2 currents in the post-midnight sector. THEMIS spacecraft data from the pre-midnight sector display multiple high speed flows and dipolarization features associated with high levels of geomagnetic activity, whereas four GOES geosynchronous spacecraft show multiple injections and dipolarization features. Magnetic field line tracing suggests that the magnetospheric location of the omega bands is at or just beyond geosynchronous orbit. We discuss in detail two potential source mechanisms for the omega bands: plasma sheet velocity shears and high speed flows in the magnetotail and relate the available data to those mechanisms. Our data and a magnetohydrodynamic (MHD) simulation support high speed flows in the magnetotail as the most likely generation mechanism, although the distribution of the magnetotail spacecraft does not provide unambiguous support for our interpretation of the source mechanism.
The Source of Auroral Omegas
2022, Journal of Geophysical Research: Space Physics
Omega Band Magnetospheric Source Location: A Statistical Model-Based Study
2021, Journal of Geophysical Research: Space Physics
Polar substorm on 7 December 2015: Preonset phenomena and features of auroral breakup
2020, Annales Geophysicae
Physical Processes of Meso-Scale, Dynamic Auroral Forms
2020, Space Science Reviews

View all citing articles on Scopus

View full text

Auroral torch structures: results of optical observations

Abstract

Planet. Space Sci.

Planet. Space Sci.

Planet. Space Sci.

Planet. Space Sci.

Planet. Space Sci.

J. atmos. terr. Phys.

Planet. Space Sci.

A study of auroral displays photographed from the DMSP-2 satellite and from Alaska meridian chain of stations

Space Sci. Rev.

Joint two-dimensional of ground magnetic and ionospheric electric currents associated with auroral currents, 5. Current system associated with eastward drifting omega bands

J. Geophys.

Spatially inhomogeneous current configurations as seen by the Scandinavian Magnetometer Array

Multi-method observations and modeling of the three dimensional current associated with a very strong Ps6 event

J. Geophys.

Three-dimensional mapping of the aurora from digitized all-sky pictures

Perturbation magnetic fields and current systems associated with eastward drifting auroral structures

J. geophys. Res.