Persistent, widespread pulsating aurora: A case study

Jones, S. L.; Lessard, M.; Rychert, Kevin M.; Spanswick, E.; Donovan, E.; Jaynes, Allison

doi:10.1002/jgra.50301

Cited by 47 publications

(67 citation statements)

References 41 publications

(65 reference statements)

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“…We suggest that the PAP might connect to a cluster of flux tubes that embed a concentrated low‐energy ion structure. Assuming that the auroral outflows intensify with the substorm onset [ Wilson et al ., ], and considering that the establishment of a cold plasma flux tube requires a timescale of inter‐hemispheric flowing of low‐energy ions (tens of minutes up to ≥1 h), the scenario proposed above is compatible with the fact that the peak occurrence of pulsating auroras usually appears in the late recovery phase of a substorm and may remain beyond the recovery phase [ Jones et al ., , ].…”

Section: Discussionmentioning

confidence: 99%

Low‐energy ion precipitation structures associated with pulsating auroral patches

et al. 2015

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Pulsating auroras often appear in forms of geo‐stable or slowly convecting “patches.” These patches can maintain their rough shape and size over many sequences of luminosity pulsations, yet they slowly drift with ionospheric E × B convection. Because of these characteristics, there has long been a speculation that the pulsating auroral patch (PAP) is connected to flux tubes filled with enhanced cold plasma. In this study, we perform a survey on pulsating auroral events when the footprints of low‐Earth‐orbit satellites traversed the PAPs, with a focus on the low‐energy particle signatures associated with the PAPs. As a result, we identified, in a majority (~2/3) of events, the existence of a low‐energy ion precipitation structure that is collocated with the PAP, with core energies ranging from several tens of eV up to a few hundred eV. This result supports the hypothesis that a PAP connects to flux tubes filled with enhanced cold plasma. We further propose that the plasma outflows from the ionosphere are the origin of such cold plasma flux tubes. We suggest that the PAP is formed by a combination of high‐energy electrons of a magnetospheric origin, the low‐energy plasma structure of an ionospheric origin, and certain ELF/VLF waves that are intensified and modulated in interactions with both the hot and cold plasma populations.

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Section: Discussionmentioning

confidence: 99%

Low‐energy ion precipitation structures associated with pulsating auroral patches

et al. 2015

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“…The coverage of the THEMIS ASI array is extensive. Under ideal meteorological and geomagnetic conditions, such as those described in Jones et al (2013), it would be possible to produce a map of convection covering the majority of Canada and Alaska. Pulsating auroral patches arise from wave-particle interactions with cold plasma located in the region of the magnetosphere where magnetic field lines transition from tail-like to dipolar.…”

Section: Future Workmentioning

confidence: 99%

“…Pulsating aurora is characterized by quasi-periodic variations in intensity and precipitating electrons with energies on the order of a few keV to several tens of keV (Johnstone, 1978). This type of aurora is most commonly seen in the morning sector auroral oval and persists for 1.5 h on average (Jones et al, 2011) but has been observed to last upwards of 15 h (Jones et al, 2013). Pulsating aurora often, but not exclusively, has an irregular patchy structure, an example of which can be seen in Fig.…”

Section: Introductionmentioning

confidence: 99%

Tracking patchy pulsating aurora through all-sky images

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 events in these data and for the automatic determination of the velocity of individual patches from that data. As a first step towards this, we have implemented an automatic technique for determining patch velocities from sequences of images from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) all-sky imager (ASI) and applied it to many pulsating aurora events. Here we demonstrate the use of this technique and present the initial results, including a comparison between ewograms (eastwest keograms) and time series of patch position as determined by the algorithm. We discuss the implications of this technique for remote sensing convection in the inner magnetosphere.

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“…Auroral pulsations are long-lasting events; studies show that they can last for more than 15 h (Jones et al, 2013). Thus, they constitute a significant amount of energy transfer from the magnetosphere to the ionosphere.…”

Section: Introductionmentioning

confidence: 99%

Variations in energy, flux, and brightness of pulsating aurora measured at high time resolution

et al. 2017

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Abstract. High-resolution multispectral optical and incoherent scatter radar data are used to study the variability of pulsating aurora. Two events have been analysed, and the data combined with electron transport and ion chemistry modelling provide estimates of the energy and energy flux during both the ON and OFF periods of the pulsations. Both the energy and energy flux are found to be reduced during each OFF period compared with the ON period, and the estimates indicate that it is the number flux of foremost higher-energy electrons that is reduced. The energies are found never to drop below a few kilo-electronvolts during the OFF periods for these events. The high-resolution optical data show the occurrence of dips in brightness below the diffuse background level immediately after the ON period has ended. Each dip lasts for about a second, with a reduction in brightness of up to 70 % before the intensity increases to a steady background level again. A different kind of variation is also detected in the OFF period emissions during the second event, where a slower decrease in the background diffuse emission is seen with its brightness minimum just before the ON period, for a series of pulsations. Since the dips in the emission level during OFF are dependent on the switching between ON and OFF, this could indicate a common mechanism for the precipitation during the ON and OFF phases. A statistical analysis of brightness rise, fall, and ON times for the pulsations is also performed. It is found that the pulsations are often asymmetric, with either a slower increase of brightness or a slower fall.

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Persistent, widespread pulsating aurora: A case study

Cited by 47 publications

References 41 publications

Low‐energy ion precipitation structures associated with pulsating auroral patches

Low‐energy ion precipitation structures associated with pulsating auroral patches

Tracking patchy pulsating aurora through all-sky images

Variations in energy, flux, and brightness of pulsating aurora measured at high time resolution

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