DMSP Observations of High‐Latitude Dayside Aurora (HiLDA)

Cai, Lei; Kullén, Anita; Zhang, Y.; Karlsson, Tomas; Vaivads, A.

doi:10.1029/2020ja028808

Cited by 7 publications

(22 citation statements)

References 77 publications

(224 reference statements)

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“…We note that no ions are associated with the inverted‐V structure, consistent with similar observations by Cai et al. (2021). Narrower inverted‐V structures are seen to be associated with negative gradients in V ⊥ where the small‐scale but large‐amplitude fluctuations are seen, both within the sunward flow region and the dawnside antisunward flow region.…”

Section: Observationssupporting

confidence: 93%

“…As F17 traverses from sunward to antisunward flow at 13:06 UT, a clear, broad inverted-V signature is seen in the electrons, co-located with a region of pre-noon auroral emission (arrow labeled 1). We note that no ions are associated with the inverted-V structure, consistent with similar observations by Cai et al (2021). Narrower inverted-V structures are seen to be associated with negative gradients in V ⊥ where the small-scale but large-amplitude fluctuations are seen, both within the sunward flow region and the dawnside antisunward flow region.…”

Section: Observationssupporting

confidence: 90%

“…The pre‐noon auroral blob (a) associated with upward FAC identified in Figure 5 is the high‐latitude dayside aurora (HiLDA) discussed in case studies by Frey (2007) and Cai et al. (2021) and statistically by Carter et al. (2018).…”

Section: Observationsmentioning

confidence: 91%

“…The pre-noon auroral blob (a) associated with upward FAC identified in Figure 5 is the high-latitude dayside aurora (HiLDA) discussed in case studies by Frey (2007) and Cai et al (2021) and statistically by Carter et al (2018). HiLDAs are produced by the upward FAC associated with the clockwise vorticity of the NBZ reverse convection pattern, as can be seen by comparing the velocity panel in Figure 6 with the electron precipitation panel at the time span where the large inverted-V structure appears (13:05:30-13:07:00).…”

Section: Observationsmentioning

confidence: 97%

“…Auroral dynamics help to shine light on the complicated processes that occur under NBZ conditions (Fear, 2021; Hosokawa et al., 2020; Kullen, 2012; Zhu et al., 1997). NBZ auroral features can include a cusp spot (Carter et al., 2020; Frey et al., 2002; Milan et al., 2000b), high latitude dayside auroras or HiLDAs (Cai et al., 2021; Carter et al., 2018; Frey, 2007; Han et al., 2020; Zhang et al., 2021), and transpolar arcs (e.g., Carter et al., 2017; Cumnock & Blomberg, 2004; Cumnock et al., 2002; Fear et al., 2014; Frank et al., 1982; Kullen et al., 2002; Milan et al., 2005). Under purely NBZ conditions ( B Y ≈ 0), when DLR is expected to occur, the polar regions can become filled with multiple sun‐aligned arcs, also known as cusp‐aligned arcs due to their characteristic pattern (Zhang et al., 2016), which are as yet poorly understood (e.g., Zhang et al., 2020).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Lobe Reconnection and Cusp‐Aligned Auroral Arcs

et al. 2022

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Following the St. Patrick's Day (17 March) geomagnetic storm of 2013, the interplanetary magnetic field had near‐zero clock angle for almost two days. Throughout this period multiple cusp‐aligned auroral arcs formed in the polar regions; we present observations of, and provide a new explanation for, this poorly understood phenomenon. The arcs were observed by auroral imagers onboard satellites of the Defense Meteorological Satellite Program. Ionospheric flow measurements and observations of energetic particles from the same satellites show that the arcs were produced by inverted‐V precipitation associated with upward field‐aligned currents (FACs) at shears in the convection pattern. The large‐scale convection pattern revealed by the Super Dual Auroral Radar Network and the corresponding FAC pattern observed by the Active Magnetosphere and Planetary Electrodynamics Response Experiment suggest that dual‐lobe reconnection was ongoing to produce significant closure of the magnetosphere. However, we propose that once the magnetosphere became nearly closed complicated lobe reconnection geometries arose that produced interleaving of regions of open and closed magnetic flux and spatial and temporal structure in the convection pattern that evolved on timescales shorter than the orbital period of the DMSP spacecraft. This new model naturally explains many features of cusp‐aligned arcs, including why they focus in from the nightside toward the cusp region.

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Section: Observationssupporting

confidence: 93%

Section: Observationssupporting

confidence: 90%

Section: Observationsmentioning

confidence: 91%

Section: Observationsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Lobe Reconnection and Cusp‐Aligned Auroral Arcs

et al. 2022

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An Auroral Signature of the Duskside Boundary of the Cusp

et al. 2022

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The cusp is a region in which the solar wind plasma can directly penetrate into the ionosphere. Most previous studies mainly focused on the low‐ and high‐latitude boundaries of the cusps, the identification of the dawnside and duskside boundaries of them appears to be questionable. The auroras are the ionospheric manifestations of solar‐terrestrial energy coupling. This paper presents a new approach to diagnose the duskside boundary of the cusp with the observation of a particular polar cap arc (PCA) located near the ∼1500 magnetic local time sector (15MLT‐PCA). Using measurements from Defense Meteorological Satellite Program satellite, we selected several 15MLT‐PCA examples where the satellite flew over different regions and analyze the particle characteristics. We identified the precipitating particles in dawnside and duskside regions next to 15MLT‐PCA are from the low latitude boundary layer/cusp and boundary plasma sheet/central plasma sheet respectively. The statistical result further confirms our findings. Therefore, we proposed that 15MLT‐PCA can be used as an identifiable optical signature of the duskside boundary of the cusp. This paper provides a valuable approach to identify the cusp boundaries, and the results are critical for understanding the generation mechanism of 15MLT‐PCA.

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Ionospheric Conductances Due To Electron and Ion Precipitations: A Comparison Between EISCAT and DMSP Estimates

Wang,

Cai,

Aikio

et al. 2024

JGR Space Physics

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Energetic particle precipitation is the major source of electron production that controls the ionospheric Pedersen and Hall conductances at high latitudes. Many studies use empirical formulas to estimate conductances. The particle precipitation spectra measured by the Defense Meteorological Satellite Program (DMSP) Special Sensor J are often used as the input to the empirical formulas. In this study, we evaluate the empirical formulas of ionospheric conductances during four different types of auroral precipitation conditions based on 63 conjugate events observed by DMSP and EISCAT. The conductances calculated from the DMSP data with the empirical formulas are compared with those based on EISCAT measurements with the standard equations. The best correlation between these two is found when the empirical Robinson formulas (Robinson et al., 1987, https://doi.org/10.1029/ja092ia03p02565) are used in the presence of diffuse electron precipitation without ions. In the presence of ion precipitation, the correlation coefficients are smaller, but the correlation improves when the Galand formulas (Galand & Richmond, 2001, https://doi.org/10.1029/1999ja002001) are used to estimate the contribution of ion precipitation to the conductances. We also found that pure ion precipitation can cause the increase of conductances up to 2–7 S for Pedersen and 2.5–10 S for Hall conductances, which is positively correlated with the auroral electrojet index. Overall, the empirical formulas applied to the DMSP particle spectra underestimate the ionospheric conductances.

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DMSP Observations of High‐Latitude Dayside Aurora (HiLDA)

Cited by 7 publications

References 77 publications

Lobe Reconnection and Cusp‐Aligned Auroral Arcs

Lobe Reconnection and Cusp‐Aligned Auroral Arcs

An Auroral Signature of the Duskside Boundary of the Cusp

Ionospheric Conductances Due To Electron and Ion Precipitations: A Comparison Between EISCAT and DMSP Estimates

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