Dayside Aurora

Frey, H. U.; Han, Desheng; Kataoka, Ryuho; Lessard, M.; Milan, S. E.; Nishimura, Y.; Strangeway, R. J.; Zou, Ying

doi:10.1007/s11214-019-0617-7

Cited by 38 publications

(52 citation statements)

References 170 publications

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“…Plasma drift measurements in the northern hemisphere showed two narrow regions of sunward flows adjacent to an anti-sunward flow at the location of the transpolar arc. The additional presence of a bright proton aurora cusp spot (Frey et al 2019) further supported the overall picture of a 4-cell convection pattern during northward IMF with the arc located between the cells ). A similar convection pattern was observed in the southern hemisphere but as it was not related to any visible aurora or particle precipitation it appeared that the theta aurora was a non-conjugate phenomenon (Østgaard et al 2003).…”

Section: Interhemispheric Symmetry/asymmetrysupporting

confidence: 63%

“…PMAFs are small polar cap arcs that split off the dayside oval and move poleward within a few minutes until they disappear (Fasel 1995;Milan et al 2000), and are generally believed to be caused by flux transfer events (Frey 2007, and references therein). A detailed discussion of PMAFs can be found in Frey et al (2019). In several of Carter et al's (2015) ideas could be confirmed for a larger dataset.…”

Section: Dayside Reconnection For Tpamentioning

confidence: 81%

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Aurora in the Polar Cap: A Review

et al. 2020

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This paper reviews our current understanding of auroral features that appear poleward of the main auroral oval within the polar cap, especially those that are known as Sunaligned arcs, transpolar arcs, or theta auroras. They tend to appear predominantly during periods of quiet geomagnetic activity or northwards directed interplanetary magnetic field (IMF). We also introduce polar rain aurora which has been considered as a phenomenon on open field lines. We describe the morphology of such auroras, their development and Auroral Physics Edited by 15 Page 2 of 44 K. Hosokawa et al.dynamics in response to solar wind-magnetosphere coupling processes, and the models that have been developed to explain them.

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Section: Interhemispheric Symmetry/asymmetrysupporting

confidence: 63%

Section: Dayside Reconnection For Tpamentioning

confidence: 81%

Aurora in the Polar Cap: A Review

et al. 2020

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“…The reconnection creates a downward current into the cusp, which also drives an upward current over the HiLDA, and both currents are connected by Pedersen currents in the high‐conductivity sunlit summer ionosphere. The low solar wind density reduces the number of available current carriers (electrons) in the upward field‐aligned current leg, so the system sets up an accelerating potential in order to drive more of the available electrons into the loss cone to keep the current going (Frey et al, 2019). Based on the observational results given in this paper, we suppose that a different mechanism generates the 15MLT‐PCA.…”

Section: Discussionmentioning

confidence: 99%

A New Type of Polar Cap Arc Observed in the ~1500 MLT Sector: 1. Northern Hemisphere Observations

Han

Feng

Zhang

et al. 2020

Geophysical Research Letters

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A new type of polar cap aurora observed in~1500 MLT sector, abbreviated as 15MLT-PCA, is identified on examining the long-term spectrographic imager observations on the DMSP satellite over the Northern Hemisphere. Apparent dependencies of 15MLT-PCA on the solar cycle, season, universal time, and interplanetary magnetic field (IMF) are presented, which indicate that the 15MLT-PCA occurs in the northern summer under conditions of large dipole tilt angle, long-lasting positive IMF B y , and predominant negative B x. The IMF B z and other solar wind conditions show less control over the occurrence of 15MLT-PCA. The particle precipitations of 15MLT-PCA show magnetosheath-like or mantle-like properties with the ions showing clear energy dispersion property. We suggest that the 15MLT-PCA is caused by reconnection between a twisted lobe field line and an antisunward IMF field line, which differs from the mechanism for High-latitude dayside aurora (HiLDA) that share some common observational features with the 15MLT-PCA.

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“…Precipitation of both protons and electrons at auroral energies (up to a few tens of keV) takes place in the cusps and leads to dayside auroral emissions mostly in the Oxygen 630.0 nm (red) and 557.7 nm (green) lines (e.g., Jacobsen et al, 1990), but also UV emissions (Doppler-shifted Ly-a emission line) associated with proton precipitation (e.g., Frey et al, 2002). Recently, Frey et al (2019) provided an extensive review of dayside aurora, discussing in particular cusp aurora during various types of solar wind driving, complementing their previous review (Frey, 2007).…”

Section: Introductionmentioning

confidence: 99%

Hybrid-Vlasov simulation of auroral proton precipitation in the cusps: Comparison of northward and southward interplanetary magnetic field driving

Grandin

Turc

Battarbee

et al. 2020

J. Space Weather Space Clim.

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Particle precipitation is a central aspect of space weather, as it strongly couples the magnetosphere and the ionosphere and can be responsible for radio signal disruption at high latitudes. We present the first hybrid-Vlasov simulations of proton precipitation in the polar cusps. We use two runs from the Vlasiator model to compare cusp proton precipitation fluxes during southward and northward interplanetary magnetic field (IMF) driving. The simulations reproduce well-known features of cusp precipitation, such as a reverse dispersion of precipitating proton energies, with proton energies increasing with increasing geomagnetic latitude under northward IMF driving, and a nonreversed dispersion under southward IMF driving. The cusp is also found more polewards in the northward IMF simulation than in the southward IMF simulation. In addition, we find that the bursty precipitation during southward IMF driving is associated with the transit of flux transfer events in the vicinity of the cusp. In the northward IMF simulation, dual lobe reconnection takes place. As a consequence, in addition to the high-latitude precipitation spot associated with the lobe reconnection from the same hemisphere, we observe lower-latitude precipitating protons which originate from the opposite hemisphere's lobe reconnection site. The proton velocity distribution functions along the newly closed dayside magnetic field lines exhibit multiple proton beams travelling parallel and antiparallel to the magnetic field direction, which is consistent with previously reported observations with the Cluster spacecraft. In both runs, clear electromagnetic ion cyclotron waves are generated in the cusps and might further increase the calculated precipitating fluxes by scattering protons to the loss cone in the low-altitude cusp. Global kinetic simulations can improve the understanding of space weather by providing a detailed physical description of the entire near-Earth space and its internal couplings.

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Dayside Aurora

Cited by 38 publications

References 170 publications

Aurora in the Polar Cap: A Review

Aurora in the Polar Cap: A Review

A New Type of Polar Cap Arc Observed in the ~1500 MLT Sector: 1. Northern Hemisphere Observations

Hybrid-Vlasov simulation of auroral proton precipitation in the cusps: Comparison of northward and southward interplanetary magnetic field driving

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