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Compared to the recently improved understanding of nightside diffuse aurora,the mechanism(s) responsible for dayside diffuse aurora remains poorlyunderstood. While dayside chorus has been thought as a potential majorcontributor to dayside diffuse auroral precipitation, quantitative analysesof the role of chorus wave scattering have not been carefully performed. Inthis study we investigate a dayside diffuse auroral intensification eventobserved by the Chinese Arctic Yellow River Station (YRS) all-sky imagers(ASI) on 7 January 2005 and capture a substantial increase in diffuseauroral intensity at the 557.7 nm wavelength that occurred over almost theentire ASI field-of-view near 09:24 UT, i.e., ~12:24 MLT. Computationof bounce-averaged resonant scattering rates by dayside chorus emissionsusing realistic magnetic field models demonstrates that dayside chorusscattering can produce intense precipitation losses of plasma sheetelectrons on timescales of hours (even approaching the strong diffusionlimit) over a broad range of both energy and pitch angle, specifically, from~1 keV to 50 keV with equatorial pitch angles from the loss cone to upto ~85° depending on electron energy. Subsequent estimate of losscone filling index indicates that the loss cone can be substantially filled,due to dayside chorus driven pitch angle scattering, at a rate of ≥0.8for electrons from ~500 eV to 50 keV that exactly covers theprecipitating electrons for the excitation of green-line diffuse aurora.Estimate of electron precipitation flux at different energy levels, based onloss cone filling index profile and typical dayside electron distributionobserved by THEMIS spacecraft under similar conditions, gives a totalprecipitation electron energy flux of the order of 0.1 erg cm<sup>−2</sup> s<sup>−1</sup> with~1 keV characteristic energy (especially when using T01s), which canbe very likely to cause intense green-line diffuse aurora activity on thedayside. Therefore, dayside chorus scattering in the realistic magneticfield can greatly contribute to the YRS ASI observed intensification ofdayside green-line aurora. Besides wave induced scattering and changes inthe ambient magnetic field, variations in associated electron flux can alsocontribute to enhanced diffuse aurora emissions, the possibility of which wecannot exactly rule out due to lack of simultaneous observations ofmagnetospheric particles. Since the geomagnetic activity level was ratherlow during the period of interest, it is reasonable to infer that changes inthe associated electron flux in the magnetosphere should be small, andconsequently its contribution to the observed enhanced diffuse auroralactivity should be small as well. Our results support the scenario thatdayside chorus could play a major role in the production of dayside diffuseaurora, and also demonstrate that changes in magnetospheric magnetic fieldshould be considered to reasonably interpret observations of dayside diffuseaurora

Intensification of dayside diffuse auroral precipitation: contribution of dayside Whistler-mode chorus waves in realistic magnetic fields