Microscopic Observations of Pulsating Aurora Associated With Chorus Element Structures: Coordinated Arase Satellite‐PWING Observations

Abstract

Rapid (<1 s) intensity modulation of pulsating auroras is caused by successive chorus elements as a response to wave‐particle interactions in the magnetosphere. Here we found that a pulsating auroral patch responds to the time spacing for successive chorus elements and possibly to chorus subpacket structures with a time scale of tens of milliseconds. These responses were identified from coordinated Arase satellite and ground (Gakona, Alaska) observations with a high‐speed auroral imager (100 Hz). The temporal variations of auroral intensity in a few‐hertz frequency range exhibited a spatial concentration at the lower‐latitude edge of the auroral patch. The spatial evolution of the auroral patch showed repeated expansion/contraction with tens of kilometer scales in the ionosphere, which could be spatial behaviors in the wave‐particle interactions. These observations indicate that chorus elements evolve coherently within the auroral patch, which is approximately 900 km in the radial and longitudinal directions at the magnetic equator.

Multiple time-scale beats in aurora: precise orchestration via magnetospheric chorus waves

“…More recently, such a correlative behavior was captured for the first time during a similar event of ground-satellite conjunction 38 . By comparing the two cases showing clear and unclear internal modulations of PsA, we succeeded in proving that less-structured "hiss-like" chorus emission 35,36 produces PsAs without the ~3 Hz internal modulation.…”

Statistical Analysis of Transverse Size of Lower Band Chorus Waves Using Simultaneous Multisatellite Observations

“…Moreover, chorus waves are one of the most important loss mechanisms of plasma sheet electrons via pitch angle scattering (e.g., Horne et al, ). The scattered electrons into the upper atmosphere could then generate microbursts (e.g., Breneman et al, ; Nakamura et al, ; Shumko et al, ), pulsating aurora (e.g., W. Li et al, ; Nishimura et al, ; Nishimura, Bortnik, Li, Thorne, Lyons, et al, ; Nishimura, Bortnik, Li, Thorne, Chen, et al, ; Ozaki et al, , ), and diffuse aurora (e.g., Ni et al, ; Thorne et al, ).…”

“…At a higher L shell, that is, L ~ 11, Agapitov et al () showed a case with a larger scale size of chorus element, around 3,000 km, using Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations. Moreover, the scale size of chorus waves is estimated by mapping the size of microburst and pulsating aurora onto the equatorial plane (e.g., Breneman et al, ; Nishimura, Bortnik, Li, Thorne, Lyons, et al, ; Nishimura, Bortnik, Li, Thorne, Chen, et al, ; Ozaki et al, , ; Shumko et al, ). On the nightside at L ~ 8, the latitudinal (longitudinal) size of pulsating aurora is found to be a few tens (hundreds) kilometers, which is roughly 3,000–7,000 km when mapping onto the equatorial plane (Nishimura, Bortnik, Li, Thorne, Chen, et al, ).…”

“…On the nightside at L ~ 8, the latitudinal (longitudinal) size of pulsating aurora is found to be a few tens (hundreds) kilometers, which is roughly 3,000–7,000 km when mapping onto the equatorial plane (Nishimura, Bortnik, Li, Thorne, Chen, et al, ). Using a similar method, Ozaki et al () estimated the scale size of chorus wave to be smaller, ~900 km at L ~ 5. Shumko et al () showed the scale size of microburst to be ~50 and 30 km in the latitudinal and longitudinal directions, respectively (from two points FIREBIRD CubeSat measurements of bouncing microburst at L = 4.7), and the corresponding chorus spatial extent at the geomagnetic equator is estimated to be 500–550 km.…”

“…Li et al, 2007;Li, Mourenas, et al, 2014;Li, Thorne, et al, 2014;Ma et al, 2018;Meredith et al, 2003;Shen et al, 2017;Thorne et al, 2013;Tu et al, 2014;Turner et al, 2019;Xiao et al, 2014). Moreover, chorus waves are one of the most important loss mechanisms of plasma sheet electrons via pitch angle scattering (e.g., Horne et al, 2003 could then generate microbursts (e.g., Breneman et al, 2017;Nakamura et al, 2000;Shumko et al, 2018), pulsating aurora (e.g., W. Li et al, 2012;Nishimura et al, 2010;Nishimura, Bortnik, Li, Thorne, Chen, et al, 2011;Ozaki et al, 2018Ozaki et al, , 2019, and diffuse aurora (e.g., Ni et al, 2008;Thorne et al, 2010).…”