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1. Role of IMF B y in the prompt electric field disturbances over equatorial ionosphere during a space weather event: IMF B y AND PROMPT PENETRATION E-FIELD

   https://doi.org/10.1002/2016JA022781  

   Chakrabarty, D. ; Hui, Debrup ; Rout, Diptiranjan ; Sekar, R. ; Bhattacharyya, Archana ; Reeves, G. D. ; Ruohoniemi, J. M. ( January 2017 , Journal of Geophysical Research: Space Physics)
2. Explicit IMF B y ‐Dependence in Geomagnetic Activity: Quantifying Ionospheric Electrodynamics

   https://doi.org/10.1029/2021JA029202  

   Holappa, L. ; Robinson, R. M. ; Pulkkinen, A. ; Asikainen, T. ; Mursula, K. ( April 2021 , Journal of Geophysical Research: Space Physics)

   null (Ed.)
3. The Growth of Ring Current/SYM‐H Under Northward IMF B z Conditions Present During the 21–22 January 2005 Geomagnetic Storm

   https://doi.org/10.1029/2023SW003489  

   Rout, Diptiranjan ; Patra, S. ; Kumar, S. ; Chakrabarty, D. ; Reeves, G. D. ; Stolle, C. ; Pandey, K. ; Chakraborty, S. ; Spencer, E. A. ( October 2023 , Space Weather)

   The total energy transfer from the solar wind to the magnetosphere is governed by the reconnection rate at the magnetosphere edges as the Z‐component of interplanetary magnetic field (IMFB_z) turns southward. The geomagnetic storm on 21–22 January 2005 is considered to be anomalous as the SYM‐H index that signifies the strength of ring current, decreases and had a sustained trough value of −101 nT lasting more than 6 hr under northward IMFB_zconditions. In this work, the standard WINDMI model is utilized to estimate the growth and decay of magnetospheric currents by using several solar wind‐magnetosphere coupling functions. However, it is found that the WINDMI model driven by any of these coupling functions is not fully able to explain the decrease of SYM‐H under northward IMFB_z. A dense plasma sheet along with signatures of a highly stretched magnetosphere was observed during this storm. The SYM‐H variations during the entire duration of the storm were only reproduced after modifying the WINDMI model to account for the effects of the dense plasma sheet. The limitations of directly driven models relying purely on the solar wind parameters and not accounting for the state of the magnetosphere are highlighted by this work.

    

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4. Effect of IMF B y on the Entry of Solar Wind Ions Into the Near‐Earth Tail Lobe: Global Hybrid Simulation and MMS Observation

   https://doi.org/10.1029/2022JA030800  

   Wang, Chih‐Ping ; Xing, Xiaoyan ; Wang, Xueyi ; Avanov, Levon A. ; Lin, Yu ; Strangeway, Robert J. ; Wei, H. Y. ( August 2022 , Journal of Geophysical Research: Space Physics)

   Global simulations predict that the low‐latitude mantle may be an important pathway for the solar wind entry into the tail magnetosphere close to the current sheet when interplanetary magnetic field (IMF)B_ydominates over IMFB_z. To evaluate this entry mechanism in the near‐Earth tail (X ∼ −10–−20R_E), we investigate the predictions from 3D global hybrid simulations as well as in situ observations by magnetospheric multiscale (MMS) spacecraft. The simulations predict that the low‐latitude mantle plasma can appear in the near‐Earth tail lobe extending inward approximately 5R_Efrom the flank magnetopause. The low‐latitude mantle plasma appears in the dawnside northern lobe and duskside southern lobe during positive IMFB_y, while the opposite asymmetry is seen during negative IMFB_y. After a change in the IMFB_ydirection arriving at the bow shock nose, it takes another ∼15–30 min for the asymmetry to completely reverse to the opposite sense in the near‐Earth tail. We present six MMS events in the tail lobe showing that the existence and absence of the low‐latitude mantle plasma is consistent with the predicted asymmetries. Statistical analysis of 5 years of MMS observations shows that the dependencies of the magnitudes of the lobe densities and tailward field‐aligned flow speeds on the IMFB_ydirections are consistent with the predicted contributions from the low‐latitude mantle plasma in the expected lobe regions.

    

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5. Modeled IMF B y Effects on the Polar Ionosphere and Thermosphere Coupling

   https://doi.org/10.1029/2019JA026949  

   Liu, Jing ; Burns, Alan G. ; Wang, Wenbin ; Zhang, Yongliang ( March 2020 , Journal of Geophysical Research: Space Physics)

   There is still an inadequate understanding of how the interplanetary magnetic field (IMF) east‐west component (B_y) affects thermospheric composition, and other ionospheric and thermospheric fields in a systematic way. Utilizing the state‐of‐art first‐principles Coupled Magnetosphere Ionosphere Thermosphere (CMIT) modeling and TIMED/Global Ultraviolet Imager (GUVI)‐observed ΣO/N₂covering an entire solar cycle (year 2002–2016), as well as a neutral parcel trajectory tracing technique, we emphasize that not only the direction ofB_y, but also its strength relative to the IMF north‐south component (B_z) that has important effects on high latitude convection, Joule heating, electron density, neutral winds, and neutral composition patterns in the upper thermosphere. The Northern Hemisphere convection pattern becomes more twisted for positiveB_ycases than negative cases: the dusk cell becomes more rounded compared with the dawn cell. Consequently, equatorward neutral winds are stronger during postmidnight hours in negativeB_ycases than in positiveB_ycases, creating a favorable condition for neutral composition disturbances (characterized by low ΣO/N₂) to expand to lower latitudes. This may lead to a more elongated ΣO/N₂depletion area along the morning‐premidnight direction for negativeB_yconditions compared with the positiveB_yconditions. Backward neutral parcel trajectories indicate that a lower ΣO/N₂parcel in negativeB_ycases comes from lower altitudes, as compared with that for positiveB_ycases, leading to larger enhancements of N₂in the former case.

    

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