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Journal articles on the topic 'Auroral plasma'

Author: Grafiati

Published: 6 September 2023

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1

Titova, E. E., A. G. Yahnin, O. Santolík, et al. "The relationship between auroral hiss at high altitudes over the polar caps and the substorm dynamics of aurora." Annales Geophysicae 23, no. 6 (2005): 2117–28. http://dx.doi.org/10.5194/angeo-23-2117-2005.

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Abstract. Strong variations of intensity and cutoff frequency of the auroral hiss were observed by INTERBALL-2 and POLAR satellites at high altitudes, poleward from the auroral oval. The hiss intensifications are correlated with the auroral activations during substorms and/or pseudo-breakups. The low cutoff frequency of auroral hiss increases with the distance between the aurora and the satellite footprint. Multicomponent wave measurements of the hiss emissions on board the POLAR spacecraft show that the horizontal component of the Poynting flux of auroral hiss changes its direction in good ac

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Blomberg, L. G., J. A. Cumnock, I. I. Alexeev, E. S. Belenkaya, S. Yu Bobrovnikov, and V. V. Kalegaev. "Transpolar aurora: time evolution, associated convection patterns, and a possible cause." Annales Geophysicae 23, no. 5 (2005): 1917–30. http://dx.doi.org/10.5194/angeo-23-1917-2005.

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Abstract. We present two event studies illustrating the detailed relationships between plasma convection, field-aligned currents, and polar auroral emissions, as well as illustrating the influence of the Interplanetary Magnetic Field's y-component on theta aurora development. The transpolar arc of the theta aurorae moves across the entire polar region and becomes part of the opposite side of the auroral oval. Electric and magnetic field and precipitating particle data are provided by DMSP, while the POLAR UVI instrument provides measurements of auroral emissions. Ionospheric electrostatic pote

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Miyashita, Yukinaga, and Akimasa Ieda. "Revisiting substorm events with preonset aurora." Annales Geophysicae 36, no. 5 (2018): 1419–38. http://dx.doi.org/10.5194/angeo-36-1419-2018.

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Abstract. Nishimura et al. (2010) proposed a new plasma intrusion or preonset aurora scenario of substorm triggering. In this scenario, a substorm is triggered by a fast earthward flow generated at the distant neutral line which corresponds to a preonset auroral streamer or arc in the ionosphere propagating from the auroral poleward boundary to the initial auroral brightening site, i.e., “preonset aurora”. In the present paper, we revisited three substorm events reported as being triggered by such a mechanism related to preonset auroras, based on THEMIS ground-based all-sky imager data. Unlike

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4

Sandholt, P. E., and C. J. Farrugia. "Monitoring magnetosheath-magnetosphere interconnection topology from the aurora." Annales Geophysicae 20, no. 5 (2002): 629–37. http://dx.doi.org/10.5194/angeo-20-629-2002.

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Abstract. A strong southward rotation of the IMF (BZ from 5 to -6 nT in ~ 20 s) on 4 January 1995 caused an abrupt reconfiguration of midday aurorae and plasma convection consisting of the following: (1) the red-line aurora associated with magnetosheath plasma transfer at the low-latitude magnetopause appeared at the same time that (2) the green-line aurora from precipitating energetic plasma sheet particles equatorward of the cusp (near the open-closed field line boundary) weakened visibly and shifted equatorward, (3) the high-latitude aurora during the previous northward IMF, which is associ

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Blixt, E. M., M. J. Kosch, and J. Semeter. "Relative drift between black aurora and the ionospheric plasma." Annales Geophysicae 23, no. 5 (2005): 1611–21. http://dx.doi.org/10.5194/angeo-23-1611-2005.

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Abstract. Black auroras are recognized as spatially well-defined regions within uniform diffuse aurora where the optical emission is significantly reduced. Although a well studied phenomenon, there is no generally accepted theory for black auroras. One theory suggests that black regions are formed when energetic magnetospheric electrons no longer have access to the loss cone. If this blocking mechanism drifts with the source electron population in the magnetosphere, black auroras in the ionosphere should drift eastward with a velocity that increases with the energy of the precipitating electro

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6

Yahnin, A. G., V. A. Sergeev, B. B. Gvozdevsky, and S. Vennerstrøm. "Magnetospheric source region of discrete auroras inferred from their relationship with isotropy boundaries of energetic particles." Annales Geophysicae 15, no. 8 (1997): 943–58. http://dx.doi.org/10.1007/s00585-997-0943-z.

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Abstract. According to observations, the discrete auroral arcs can sometimes be found, either deep inside the auroral oval or at the poleward border of the wide (so-called double) auroral oval, which map to very different regions of the magnetotail. To find common physical conditions for the auroral-arc generation in these magnetotail regions, we study the spatial relationship between the diffuse and discrete auroras and the isotropic boundaries (IBs) of the precipitating energetic particles which can be used to characterise locally the equatorial magnetic field in the tail. From comparison of

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7

De Keyser, J., and M. Echim. "Auroral and sub-auroral phenomena: an electrostatic picture." Annales Geophysicae 28, no. 2 (2010): 633–50. http://dx.doi.org/10.5194/angeo-28-633-2010.

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Abstract. Many auroral and sub-auroral phenomena are manifestations of an underlying magnetosphere-ionosphere coupling. In the electrostatic perspective the associated auroral current circuit describes how the generator (often in the magnetosphere) is connected to the load (often in the ionosphere) through field-aligned currents. The present paper examines the generic properties of the current continuity equation that characterizes the auroral circuit. The physical role of the various elements of the current circuit is illustrated by considering a number of magnetospheric configurations, vario

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8

Borodkova, N. L., A. G. Yahnin, K. Liou, et al. "Plasma sheet fast flows and auroral dynamics during substorm: a case study." Annales Geophysicae 20, no. 3 (2002): 341–47. http://dx.doi.org/10.5194/angeo-20-341-2002.

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Abstract. Interball-1 observations of a substorm development in the mid-tail on 16 December 1998 are compared with the auroral dynamics obtained from the Polar UV imager. Using these data, the relationship between plasma flow directions in the tail and the location of the auroral activation is examined. Main attention is given to tailward and earth-ward plasma flows, interpreted as signatures of a Near Earth Neutral Line (NENL). It is unambiguously shown that in the mid-plasma sheet the flows were directed tailward when the auroral bulge developed equatorward of the spacecraft ionospheric foot

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9

Cumnock, J. A., and L. G. Blomberg. "Transpolar arc evolution and associated potential patterns." Annales Geophysicae 22, no. 4 (2004): 1213–31. http://dx.doi.org/10.5194/angeo-22-1213-2004.

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Abstract. We present two event studies encompassing detailed relationships between plasma convection, field-aligned current, auroral emission, and particle precipitation boundaries. We illustrate the influence of the Interplanetary Magnetic Field By component on theta aurora development by showing two events during which the theta originates on both the dawn and dusk sides of the auroral oval. Both theta then move across the entire polar region and become part of the opposite side of the auroral oval. Electric and magnetic field and precipitating particle data are provided by DMSP, while the P

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10

Rycroft, M. J. "Auroral plasma dynamics." Journal of Atmospheric and Terrestrial Physics 57, no. 13 (1995): 1668. http://dx.doi.org/10.1016/0021-9169(95)90035-7.

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Sandholt, P. E., and C. J. Farrugia. "The role of external triggers in flow shear arcs in the dayside aurora." Annales Geophysicae 26, no. 8 (2008): 2159–77. http://dx.doi.org/10.5194/angeo-26-2159-2008.

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Abstract. In case studies we relate dayside auroral transients to IMF By-distorted plasma convection cells based on high-resolution observations from the ground. We selected three days representing positive and negative IMF By conditions when SuperDARN returned reliable dayside convection patterns in the sector of our optical observations from Ny Ålesund, Svalbard (76° MLAT). We combine two perspectives on the dayside aurora, the local and the global. In the first we derive the fine-structure of dayside precipitation/convection as a function of magnetic latitude (MLAT) and magnetic local time

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Yahnin, A. G., I. V. Despirak, A. A. Lubchich, et al. "Indirect mapping of the source of the oppositely directed fast plasma flows in the plasma sheet onto the auroral display." Annales Geophysicae 24, no. 2 (2006): 679–87. http://dx.doi.org/10.5194/angeo-24-679-2006.

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Abstract. Data from Polar and Geotail spacecraft are combined to investigate the relationship between locations of active auroras and the magnetotail plasma sheet region where reversed fast plasma flows are generated during substorms. Using the magnetospheric magnetic field model, it is shown that at the beginning of the tailward fast flow the ionospheric footprint of the spacecraft measuring the flow tends to be located poleward of the auroral bulge. The spacecraft within the earthward flow is mapped equatorward of the poleward edge of the auroral bulge. We conclude that a source of the fast

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Sandholt, P. E., C. J. Farrugia, and W. F. Denig. "Detailed dayside auroral morphology as a function of local time for southeast IMF orientation: implications for solar wind-magnetosphere coupling." Annales Geophysicae 22, no. 10 (2004): 3537–60. http://dx.doi.org/10.5194/angeo-22-3537-2004.

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Abstract. In two case studies we elaborate on spatial and temporal structures of the dayside aurora within 08:00-16:00 magnetic local time (MLT) and discuss the relationship of this structure to solar wind-magnetosphere interconnection topology and the different stages of evolution of open field lines in the Dungey convection cycle. The detailed 2-D auroral morphology is obtained from continuous ground observations at Ny Ålesund (76° magnetic latitude (MLAT)), Svalbard during two days when the interplanetary magnetic field (IMF) is directed southeast (By>0; Bz<0). The auroral activity co

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Sandholt, P. E., J. Moen, C. J. Farrugia, et al. "Multi-site observations of the association between aurora and plasma convection in the cusp/polar cap during a southeastward(<i>B<sub>y</sub></i> <u>~</u> |<i>B<sub>z</sub></i>|) IMF orientation." Annales Geophysicae 21, no. 2 (2003): 539–58. http://dx.doi.org/10.5194/angeo-21-539-2003.

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Abstract. In a case study we demonstrate the spatiotemporal structure of aurora and plasma convection in the cusp/polar cap when the interplanetary magnetic field (IMF) Bz < 0 and By ~ | Bz | (clock angle in GSM Y - Z plane: ~ 135°). This IMF orientation elicited a response different from that corresponding to strongly northward and southward IMF. Our study of this "intermediate state" is based on a combination of ground observations of optical auroral emissions and ionospheric plasma convection. Utilizing all-sky cameras at NyAlesund, Svalbard and Heiss Island (Russian arctic), we are able

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Sandholt, P. E., and C. J. Farrugia. "Poleward moving auroral forms (PMAFs) revisited: responses of aurorae, plasma convection and Birkeland currents in the pre- and postnoon sectors under positive and negative IMF <I>B<sub>y</sub></I> conditions." Annales Geophysicae 25, no. 7 (2007): 1629–52. http://dx.doi.org/10.5194/angeo-25-1629-2007.

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Abstract. Using five case studies, we investigate the dynamical evolution of dayside auroral precipitation in relation to plasma convection, classifying it by the IMF By component and position with respect to noon. Auroral observations were made by meridian scanning photometers (MSPs) and an all-sky camera (ASC) in Ny Ålesund, Svalbard at 76° MLAT, while the spatial structure of the ionospheric plasma convection is inferred from SuperDARN radars and ion drift observations from spacecraft in polar orbit. The IMF configuration of major interest here is one pointing southward and with a dominant

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Sandholt, P. E., C. J. Farrugia, and W. F. Denig. "Dayside aurora and the role of IMF ∣<i>B<sub>y</sub></i>∣/∣<i>B<sub>z</sub></i>∣: detailed morphology and response to magnetopause reconnection." Annales Geophysicae 22, no. 2 (2004): 613–28. http://dx.doi.org/10.5194/angeo-22-613-2004.

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Abstract. We document the detailed spatio-temporal structure of the dayside aurora during intervals of ongoing dayside magnetopause reconnection, primarily during interplanetary magnetic field (IMF) Bz≤0 conditions. The present study is based on ground auroral observations in combination with particle precipitation data from a DMSP spacecraft. We describe auroral forms corresponding to the following particle precipitation regimes identified by Newell and Meng (1994): (i) central plasma sheet (CPS), (ii) precipitation void, (iii) dayside boundary plasma sheet (BPS), and (iv) cusp (LLBL/cusp/man

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Grono, Eric, and Eric Donovan. "Differentiating diffuse auroras based on phenomenology." Annales Geophysicae 36, no. 3 (2018): 891–98. http://dx.doi.org/10.5194/angeo-36-891-2018.

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Abstract. There is mounting evidence which suggests that pulsating auroral patches often move with convection. This study is an initial step at identifying the differences between patches that move with convection and those that do not. While many properties of pulsating patches vary, here we outline criteria for separating pulsating auroral patches into three categories based on two properties: their structural stability and the spatial extent of their pulsations. Patchy aurora is characterized by stable structures whose pulsations are limited to small regions. Patchy pulsating aurora consist

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Simmons, D. A. R., F. Sigernes, and K. Henriksen. "Geomagnetic storm and substorm aurora observed from Spitsbergen." Polar Record 31, no. 179 (1995): 375–88. http://dx.doi.org/10.1017/s0032247400027352.

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ABSTRACTThe present study confirms that the auroras of the nightside oval population consist of two main types, namely storm and substorm aurora. Storm-type aurora, which is relatively infrequent, results from bombardment of the upper ionosphere by fast particle streams generated in the solar wind by cataclysmic solar events related to coronal mass ejections. The associated turbulent plasma that is injected into the magnetosphere produces great magnetic storms of world-wide dimensions that may last for days. In contrast, substorm aurora is a frequent (almost daily) occurrence that lasts for an

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Keiling, A., V. Angelopoulos, J. M. Weygand, et al. "THEMIS ground-space observations during the development of auroral spirals." Annales Geophysicae 27, no. 11 (2009): 4317–32. http://dx.doi.org/10.5194/angeo-27-4317-2009.

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Abstract. A simultaneous observation of an auroral spiral and its generator region in the near-Earth plasma sheet is rather unlikely. Here we present such observations using the THEMIS spacecraft as well as the THEMIS ground network of all-sky imagers and magnetometers. Two consecutive auroral spirals separated by approximately 14 min occurred during a substorm on 19 February 2008. The spirals formed during the expansion phase and a subsequent intensification, and were among the brightest features in the aurora with diameters of 200–300 km. The duration for the formation and decay of each spir

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Partamies, N., K. Kauristie, E. Donovan, E. Spanswick, and K. Liou. "Meso-scale aurora within the expansion phase bulge." Annales Geophysicae 24, no. 8 (2006): 2209–18. http://dx.doi.org/10.5194/angeo-24-2209-2006.

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Abstract. We present ground-based optical, riometer and magnetometer recordings together with Polar UVI and GOES magnetic field observations of a substorm that occurred over Canada on 24 November 1997. This event involved a clear optical onset followed by poleward motion of the aurora as a signature of an expanding auroral bulge. During the expansion phase, there were three distinct types of meso-scale (10–1000 km) auroral structures embedded in the bulge: at first a series of equatorward moving auroral arcs, followed by a well-defined spiral pair, and finally north-south directed aurora (a st

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Waite, J. Hunter, John T. Clarke, R. J. Walker, et al. "Jupiter’s Aurora: Solar Wind and Rotational Influences." Highlights of Astronomy 12 (2002): 606. http://dx.doi.org/10.1017/s1539299600014362.

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AbstractJovian auroral emissions are observed at infrared, visible, ultraviolet, and x-ray wavelengths. As at Earth, pitch-angle scattering of energetic particles into the atmospheric loss cone and the acceleration of current-carrying electrons in field-aligned currents both play a role in exciting the auroral emissions. The x-ray aurora is believed to result principally from heavy ion precipitation, while the ultraviolet aurora is produced predominantly by precipitating energetic electrons. The magnetospheric processes responsible for the aurora are driven primarily by planetary rotation. Acc

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Sergienko, T., I. Sandahl, B. Gustavsson, L. Andersson, U. Brändström, and Å. Steen. "A study of fine structure of diffuse aurora with ALIS-FAST measurements." Annales Geophysicae 26, no. 11 (2008): 3185–95. http://dx.doi.org/10.5194/angeo-26-3185-2008.

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Abstract. We present results of an investigation of the fine structure of the night sector diffuse auroral zone, observed simultaneously with optical instruments (ALIS) from the ground and the FAST electron spectrometer from space 16 February 1997. Both the optical and particle data show that the diffuse auroral zone consisted of two regions. The equatorward part of the diffuse aurora was occupied by a pattern of regular, parallel auroral stripes. The auroral stripes were significantly brighter than the background luminosity, had widths of approximately 5 km and moved southward with a velocity

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Kozlovsky, A., V. Safargaleev, N. Østgaard, et al. "On the motion of dayside auroras caused by a solar wind pressure pulse." Annales Geophysicae 23, no. 2 (2005): 509–21. http://dx.doi.org/10.5194/angeo-23-509-2005.

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Abstract. Global ultraviolet auroral images from the IMAGE satellite were used to investigate the dynamics of the dayside auroral oval responding to a sudden impulse (SI) in the solar wind pressure. At the same time, the TV all-sky camera and the EISCAT radar on Svalbard (in the pre-noon sector) allowed for detailed investigation of the auroral forms and the ionospheric plasma flow. After the SI, new discrete auroral forms appeared in the poleward part of the auroral oval so that the middle of the dayside oval moved poleward from about 70° to about 73° of the AACGM latitude. This poleward shif

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Falthammar, C. G. "Physics of the Aurora." Geofísica Internacional 30, no. 4 (1991): 197–211. http://dx.doi.org/10.22201/igeof.00167169p.1991.30.4.1227.

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La aurora, ya de por si fascinante por su belleza y la multitud de sus formas, ha resultado aún más fascinante en términos de la física que se puede aprender de su estudio científico. Observaciones in situ de la aurora y de los fenómenos relacionados con ella han sacado a la luz los procesos de la física de plasmas, cuya presencia tiene un profundo impacto en nuestro concepto del espacio que nos rodea. La mayoría de estos procesos están relacionados con procesos de aceleraci6n auroral. Aunque se sabe desde hace tiempo que la aurora es causada por electrones de unos cuantos keV que inciden sobr

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Volosevich, A. V., and Y. I. Galperin. "Nonlinear wave structures in collisional plasma of auroral E-region ionosphere." Annales Geophysicae 15, no. 7 (1997): 890–98. http://dx.doi.org/10.1007/s00585-997-0890-8.

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Abstract. Studies of the auroral plasma with small-scale inhomogenieties producing the VHF-radar reflections (radar aurora) when observed in conditions of the saturated Farley-Buneman instability within the auroral E region, show strong nonlinear interactions and density fluctuations of 5–15%. Such nonlinearity and high fluctation amplitudes are inconsistent with the limitations of the weak turbulence theory, and thus a theory for arbitrary amplitudes is needed. To this end, a nonlinear theory is described for electrostatic MHD moving plasma structures of arbitrary amplitude for conditions thr

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Grono, Eric, Eric Donovan, and Kyle R. Murphy. "Tracking patchy pulsating aurora through all-sky images." Annales Geophysicae 35, no. 4 (2017): 777–84. http://dx.doi.org/10.5194/angeo-35-777-2017.

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Abstract. Pulsating aurora is frequently observed in the evening and morning sector auroral oval. While the precipitating electrons span a wide range of energies, there is increasing evidence that the shape of pulsating auroral patches is controlled by structures in near-equatorial cold plasma; these patches appear to move with convection, for example. Given the tremendous and rapidly increasing amount of auroral image data from which the velocity of these patches can be inferred, it is timely to develop and implement techniques for the automatic identification of pulsating auroral patch event

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27

Safargaleev, V., T. Sergienko, H. Nilsson, et al. "Combined optical, EISCAT and magnetic observations of the omega bands/Ps6 pulsations and an auroral torch in the late morning hours: a case study." Annales Geophysicae 23, no. 5 (2005): 1821–38. http://dx.doi.org/10.5194/angeo-23-1821-2005.

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Abstract. We present here the results of multi-instrument observations of auroral torch and Ps6 magnetic pulsations, which are assumed to be the magnetic signature of the spatially periodic optical auroras known as omega bands. Data from TV and ASC cameras in Barentsburg and Ny Ålesund, EISCAT radars in Longyearbyen and Tromsø, as well as IMAGE network were used in this study. The auroral phenomenon which was considered differed from that previously discussed, as it occurred both in an unusual place (high latitudes) and at an unusual time (late morning hours). We show that this might occur due

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Miller, Steven, Hoanh An Lam, and Jonathan Tennyson. "What astronomy has learned from observations of." Canadian Journal of Physics 72, no. 11-12 (1994): 760–71. http://dx.doi.org/10.1139/p94-100.

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We review the uses to which [Formula: see text] astronomical observations have been put, in the five years since the first detection of this molecular ion in the aurorae of Jupiter. Spectroscopy of Jupiter shows that the ionospheric temperature is high (~1000 K) compared with the lower atmosphere and that auroral column densities are between 1012 and 1013 cm−2. The molecule is also distributed widely across the planet in concentrations about 10% of peak auroral densities. Imaging in [Formula: see text]-sensitive wavelengths links the aurorae to open magnetic field lines, rather than those enco

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Milan, S. E., T. K. Yeoman, M. Lester, J. Moen, and P. E. Sandholt. "Post-noon two-minute period pulsating aurora and their relationship to the dayside convection pattern." Annales Geophysicae 17, no. 7 (1999): 877–91. http://dx.doi.org/10.1007/s00585-999-0877-8.

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Abstract. Poleward-moving auroral forms, as observed by meridian-scanning photometers, in the vicinity of the cusp region are generally assumed to be the optical signature of flux transfer events. Another class of quasi-continuous, short period (1-2 min) wave-like auroral emission has been identified, closely co-located with the convection reversal boundary in the post-noon sector, which is similar in appearance to such cusp aurora. It is suggested that these short period wave-like auroral emissions, the optical signature of boundary plasma sheet precipitation in the region 1 field-aligned cur

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McWilliams, K. A., T. K. Yeoman, J. B. Sigwarth, L. A. Frank, and M. Brittnacher. "The dayside ultraviolet aurora and convection responses to a southward turning of the interplanetary magnetic field." Annales Geophysicae 19, no. 7 (2001): 707–21. http://dx.doi.org/10.5194/angeo-19-707-2001.

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Abstract. We examine the large-scale ultraviolet aurora and convection responses to a series of flux transfer events that immediately followed a sharp and isolated southward turning of the IMF. During the interval of interest, SuperDARN was monitoring the plasma convection in the dayside northern ionosphere, while the VIS Earth Camera and the Far Ul-traviolet Imager (UVI) were monitoring the northern hemisphere’s ultraviolet aurora. Reconnection signatures were seen in the SuperDARN HF radar data in the postnoon sector following a sharp southward turning of the IMF. The presence of flux transf

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Kletzing, C. A., and J. D. Scudder. "Auroral-plasma sheet electron anisotropy." Geophysical Research Letters 26, no. 7 (1999): 971–74. http://dx.doi.org/10.1029/1999gl900092.

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Hilgers, A. "The auroral radiating plasma cavities." Geophysical Research Letters 19, no. 3 (1992): 237–40. http://dx.doi.org/10.1029/91gl02938.

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Feldstein, Y. I., L. I. Gromova, M. Förster, and A. E. Levitin. "Spiral structures and regularities in magnetic field variations and auroras." History of Geo- and Space Sciences 3, no. 1 (2012): 1–31. http://dx.doi.org/10.5194/hgss-3-1-2012.

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Abstract. The conception of spiral shaped precipitation regions, where solar corpuscles penetrate the upper atmosphere, was introduced into geophysics by C. Störmer and K. Birkeland at the beginning of the last century. Later, in the course of the XX-th century, spiral distributions were disclosed and studied in various geophysical phenomena. Most attention was devoted to spiral shapes in the analysis of regularities pertaining to the geomagnetic activity and auroras. We review the historical succession of perceptions about the number and positions of spiral shapes, that characterize the spati

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Moser, Chrystal, James LaBelle, and Iver H. Cairns. "High bandwidth measurements of auroral Langmuir waves with multiple antennas." Annales Geophysicae 40, no. 2 (2022): 231–45. http://dx.doi.org/10.5194/angeo-40-231-2022.

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Abstract. The High-Bandwidth Auroral Rocket (HIBAR) was launched from Poker Flat, Alaska, on 28 January 2003 at 07:50 UT towards an apogee of 382 km in the nightside aurora. The flight was unique in having three high-frequency (HF) receivers using multiple antennas parallel and perpendicular to the ambient magnetic field, as well as very low-frequency (VLF) receivers using antennas perpendicular to the magnetic field. These receivers observed five short-lived Langmuir wave bursts lasting from 0.1–0.2 s, consisting of a thin plasma line with frequencies in the range of 2470–2610 kHz that had an

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Milan, S. E., M. Lester, N. Sato, H. Takizawa, and J. P. Villain. "Investigation of the relationship between optical auroral forms and HF radar E region backscatter." Annales Geophysicae 18, no. 6 (2000): 608–17. http://dx.doi.org/10.1007/s00585-000-0608-7.

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Abstract. The SuperDARN HF radars have been employed in the past to investigate the spectral characteristics of coherent backscatter from L-shell aligned features in the auroral E region. The present study employs all-sky camera observations of the aurora from Husafell, Iceland, and the two SuperDARN radars located on Iceland, Þykkvibær and Stokkseyri, to determine the optical signature of such backscatter features. It is shown that, especially during quiet geomagnetic conditions, the backscatter region is closely associated with east-west aligned diffuse auroral features, and that the two mov

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Feldstein, Y. I., R. D. Elphinstone, D. J. Hearn, J. S. Murphree, and L. L. Cogger. "Mapping of the statistical auroral distribution into the magnetosphere." Canadian Journal of Physics 72, no. 5-6 (1994): 266–69. http://dx.doi.org/10.1139/p94-039.

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Statistical auroral distributions are used in combination with an empirical model of the Earth's magnetic field in an attempt to determine the large-scale magnetospheric source regions for various types of auroral luminosity. The narrow ring of structured auroral emissions during magnetically quiet intervals appears to be associated with the inner region of the nightside central plasma sheet and the dayside entry layer. Under active conditions these discrete structures expand to fill the entire central plasma sheet. The high-altitude boundary plasma sheet on the other hand is more likely to be

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Uritsky, V. M., E. Donovan, A. J. Klimas, and E. Spanswick. "Collective dynamics of bursty particle precipitation initiating in the inner and outer plasma sheet." Annales Geophysicae 27, no. 2 (2009): 745–53. http://dx.doi.org/10.5194/angeo-27-745-2009.

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Abstract. Using multiscale spatiotemporal analysis of bursty precipitation events in the nighttime aurora as seen by the POLAR UVI instrument, we report a set of new statistical signatures of high- and low-latitude auroral activity, signaling a strongly non-uniform distribution of dissipation mechanism in the plasma sheet. We show that small-scale electron emission events that initiate in the equatorward portion of the nighttime auroral oval (scaling mode A1) have systematically steeper power-law slopes of energy, power, area, and lifetime probability distributions compared to the events that

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Badman, S. V., S. W. H. Cowley, J. C. Gérard, and D. Grodent. "A statistical analysis of the location and width of Saturn's southern auroras." Annales Geophysicae 24, no. 12 (2006): 3533–45. http://dx.doi.org/10.5194/angeo-24-3533-2006.

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Abstract. A selection of twenty-two Hubble Space Telescope images of Saturn's ultraviolet auroras obtained during 1997–2004 has been analysed to determine the median location and width of the auroral oval, and their variability. Limitations of coverage restrict the analysis to the southern hemisphere, and to local times from the post-midnight sector to just past dusk, via dawn and noon. It is found that the overall median location of the poleward and equatorward boundaries of the oval with respect to the southern pole are at ~14° and ~16° co-latitude, respectively, with a median latitudinal wi

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Yeoman, T. K., J. A. Davies, N. M. Wade, G. Provan, and S. E. Milan. "Combined CUTLASS, EISCAT and ESR observations of ionospheric plasma flows at the onset of an isolated substorm." Annales Geophysicae 18, no. 9 (2000): 1073–87. http://dx.doi.org/10.1007/s00585-000-1073-z.

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Abstract. On August 21st 1998, a sharp southward turning of the IMF, following on from a 20 h period of northward directed magnetic field, resulted in an isolated substorm over northern Scandinavia and Svalbard. A combination of high time resolution and large spatial scale measurements from an array of coherent scatter and incoherent scatter ionospheric radars, ground magnetometers and the Polar UVI imager has allowed the electrodynamics of the impulsive substorm electrojet region during its first few minutes of evolution at the expansion phase onset to be studied in great detail. At the expan

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Feldstein, Y. I., L. I. Gromova, J. Woch, et al. "Structure of the auroral precipitation region in the dawn sector: relationship to convection reversal boundaries and field-aligned currents." Annales Geophysicae 19, no. 5 (2001): 495–519. http://dx.doi.org/10.5194/angeo-19-495-2001.

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Abstract. Abstract. Simultaneous DMSP F7 and Viking satellite measurements of the dawnside high-latitude auroral energy electron and ion precipitation show that the region of the low and middle altitude auroral precipitation consists of three characteristic plasma regimes. The recommendation of the IAGA Working Group IIF/III4 at the IAGA Assembly in Boulder, July 1995 to decouple the nomenclature of ionospheric populations from magnetospheric population is used for their notation. The most equatorial regime is the Diffuse Auroral Zone (DAZ) of diffuse spatially unstructured precipitating elect

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Danielides, M. A., and A. Kozlovsky. "Rocket-borne investigation of auroral patches in the evening sector during substorm recovery." Annales Geophysicae 21, no. 3 (2003): 719–28. http://dx.doi.org/10.5194/angeo-21-719-2003.

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Abstract. On 11 February 1997 at 08:36 UT after a substorm onset the Auroral Turbulence 2 sounding rocket was launched from Poker Flat Research Range, Alaska into a moderately active auroral region. This experiment has allowed us to investigate evening (21:00 MLT) auroral forms at the substorm recovery, which were discrete multiple auroral arcs stretched to, the east and southeast from the breakup region, and bright auroral patches propagating westward along the arcs like a luminosity wave, which is a typical feature of the disturbed arc. The rocket crossed an auroral arc of about 40 km width,

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Despirak, I. V., T. V. Kozelova, B. V. Kozelov, and A. A. Lubchich. "OBSERVATIONS OF SUBSTORM ACTIVITY FROM THE DATA OF MAIN CAMERA SYSTEM AND THD SATELLITE IN THE PLASMA SHEET." PHYSICS OF AURORAL PHENOMENA 44 (2021): 16–19. http://dx.doi.org/10.51981/2588-0039.2021.44.003.

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We investigated an interesting case of the space-time dynamics of substorm activations (AL ~ 800 nT) on December 24, 2014, when there were simultaneous observations on the THEMIS D satellite in the plasma sheet (|X| ~ 6.2 RE) and ground-based observations on the Kola Peninsula. The development of the substorm activity in the interval of ~ 19:00 to ~ 20:00 UT was considered. In this interval, at Lovozero station (LOZ), three peaks in the Pi1B pulsations were recorded, associated with the brightening of arcs near LOZ. The first peak was observed in connection with the appearance of beads structu

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Amm, O., A. Pajunpää, and U. Brandström. "Spatial distribution of conductances and currents associated with a north-south auroral form during a multiple-substorm period." Annales Geophysicae 17, no. 11 (1999): 1385–96. http://dx.doi.org/10.1007/s00585-999-1385-6.

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Abstract. Using the method of characteristics to invert ground-based data of the ground magnetic field disturbance and of the ionospheric electric field, we obtain spatial distributions of ionospheric conductances, currents, and field-aligned currents (FACs) associated with a north-south auroral form that drifts westwards over northern Scandinavia around 2200 UT on December 2, 1977. This auroral form is one in a sequence of such north-south structures observed by all-sky cameras, and appears 14 min after the last of several breakups during that extremely disturbed night. Our analysis shows tha

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Kozlovsky, A. E., V. V. Safargaleev, J. R. T. Jussila, and A. V. Koustov. "Pre-noon high-latitude auroral arcs as a manifestation of the interchange instability." Annales Geophysicae 21, no. 12 (2003): 2303–14. http://dx.doi.org/10.5194/angeo-21-2303-2003.

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Abstract. On 7 December 2000, TV ASC camera in Barentsburg (Svalbard) observed pre-noon (at 09:00–10:00 MLT) rayed auroral arcs, which occurred at the pole-ward edge of the auroral oval after an IMF transition from By -dominated (By = + 8.8, Bz = + 4.3) to strongly northward dominated (By = + 2.7, Bz = + 8.6). The arcs appeared from the area of enhanced luminosity seen in the western (nightside) horizon, and developed to the east, progressing at a velocity of about 1.5 km/s. Simultaneously, the arcs were drifting poleward at a velocity of 300–500 m/s, whose value was equal to the F-region iono

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Nikolaev, A. V., V. A. Sergeev, N. A. Tsyganenko, et al. "A quantitative study of magnetospheric magnetic field line deformation by a two-loop substorm current wedge." Annales Geophysicae 33, no. 4 (2015): 505–17. http://dx.doi.org/10.5194/angeo-33-505-2015.

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Abstract. Substorm current wedge (SCW) formation is associated with global magnetic field reconfiguration during substorm expansion. We combine a two-loop model SCW (SCW2L) with a background magnetic field model to investigate distortion of the ionospheric footpoint pattern in response to changes of different SCW2L parameters. The SCW-related plasma sheet footprint shift results in formation of a pattern resembling an auroral bulge, the poleward expansion of which is controlled primarily by the total current in the region 1 sense current loop (I1). The magnitude of the footprint latitudinal sh

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Figueiredo, S., G. T. Marklund, T. Karlsson, et al. "Temporal and spatial evolution of discrete auroral arcs as seen by Cluster." Annales Geophysicae 23, no. 7 (2005): 2531–57. http://dx.doi.org/10.5194/angeo-23-2531-2005.

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Abstract. Two event studies are presented in this paper where intense convergent electric fields, with mapped intensities up to 1350 mV/m, are measured in the auroral upward current region by the Cluster spacecraft, at altitudes between 3 and 5 Earth radii. Both events are from May 2003, Southern Hemisphere, with equatorward crossings by the Cluster spacecraft of the pre-midnight auroral oval. Event 1 occurs during the end of the recovery phase of a strong substorm. A system of auroral arcs associated with convergent electric field structures, with a maximum perpendicular potential drop of abo

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Janhunen, P., A. Olsson, and H. Laakso. "Altitude dependence of plasma density in the auroral zone." Annales Geophysicae 20, no. 11 (2002): 1743–50. http://dx.doi.org/10.5194/angeo-20-1743-2002.

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Abstract. We study the altitude dependence of plasma depletions above the auroral region in the 5000–30 000 km altitude range using five years of Polar spacecraft potential data. We find that besides a general decrease of plasma density with altitude, there frequently exist additional density depletions at 2–4 RE radial distance, where RE is the Earth radius. The position of the depletions tends to move to higher altitude when the ionospheric footpoint is sunlit as compared to darkness. Apart from these cavities at 2–4 RE radial distance, separate cavities above 4 RE occur in the midnight sect

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Willis, D. M., G. M. Armstrong, C. E. Ault, and F. R. Stephenson. "Identification of possible intense historical geomagnetic storms using combined sunspot and auroral observations from East Asia." Annales Geophysicae 23, no. 3 (2005): 945–71. http://dx.doi.org/10.5194/angeo-23-945-2005.

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Abstract. Comprehensive catalogues of ancient sunspot and auroral observations from East Asia are used to identify possible intense historical geomagnetic storms in the interval 210 BC-AD 1918. There are about 270 entries in the sunspot catalogue and about 1150 entries in the auroral catalogue. Special databases have been constructed in which the scientific information in these two catalogues is placed in specified fields. For the purposes of this study, an historical geomagnetic storm is defined in terms of an auroral observation that is apparently associated with a particular sunspot observa

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Sakaguchi, K., K. Shiokawa, A. Ieda, et al. "Fine structures and dynamics in auroral initial brightening at substorm onsets." Annales Geophysicae 27, no. 2 (2009): 623–30. http://dx.doi.org/10.5194/angeo-27-623-2009.

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Abstract. We show four auroral initial brightening events at substorm onsets focusing on fine structures and their longitudinal dynamics, which were observed by all-sky TV cameras (30-Hz sampling) on January 2008, in Canada. For two initial brightenings started in the field of views of the cameras, we found that they started at longitudinal segments with a size of less than ~30–60 km. One brightening expanded with wavy structures and the other expanded as a straight arc. Although the two events had different structures, both brightening auroras expanded with an average speed of ~20 km/s in the

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Olsson, A., P. Janhunen, and W. K. Peterson. "Ion shell distributions as free energy source for plasma waves on auroral field lines mapping to plasma sheet boundary layer." Annales Geophysicae 22, no. 6 (2004): 2115–33. http://dx.doi.org/10.5194/angeo-22-2115-2004.

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Abstract. Ion shell distributions are hollow spherical shells in velocity space that can be formed by many processes and occur in several regions of geospace. They are interesting because they have free energy that can, in principle, be transmitted to ions and electrons. Recently, a technique has been developed to estimate the original free energy available in shell distributions from in-situ data, where some of the energy has already been lost (or consumed). We report a systematic survey of three years of data from the Polar satellite. We present an estimate of the free energy available from

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