Blar i Bergen Open Research Archive på forfatter "Gjerløv, Jesper"

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    • AE, DST, and Their SuperMAG Counterparts: The Effect of Improved Spatial Resolution in Geomagnetic Indices 

      Bergin, A.; Chapman, S.C.; Gjerløv, Jesper (Journal article; Peer reviewed, 2020)
      For decades, geomagnetic indices have been used extensively to parameterize space weather events, as input to various models and as space weather specifications. The auroral electrojet (AE) index and disturbance storm time ...

    • Birkeland current effects on high-latitude ground magnetic field perturbations 

      Laundal, Karl Magnus; Haaland, Stein; Lehtinen, Nikolai; Gjerløv, Jesper; Østgaard, Nikolai; Tenfjord, Paul; Reistad, Jone Peter; Snekvik, Kristian; Milan, Steve; Ohtani, Shin-ichi; Anderson, Brian J. (Peer reviewed; Journal article, 2015-09-18)
      Magnetic perturbations on ground at high latitudes are directly associated only with the divergence-free component of the height-integrated horizontal ionospheric current, J⊥,df. Here we show how J⊥,df can be expressed as ...

    • Directed Network of Substorms Using SuperMAG Ground‐Based Magnetometer Data 

      Orr, L; Chapman, Sandra c.; Gjerløv, Jesper (Peer reviewed; Journal article, 2019)
      We quantify the spatiotemporal evolution of the substorm ionospheric current system utilizing the SuperMAG 100+ magnetometers. We construct dynamical directed networks from this data for the first time. If the canonical ...

    • Distribution and Occurrence Frequency of dB/dt Spikes During Magnetic Storms 1980–2020 

      Schillings, A.; Palin, L.; Opgenoorth, H.J.; Hamrin, M.; Rosenqvist, L.; Gjerløv, Jesper; Juusola, Liisa; Barnes, R. (Journal article; Peer reviewed, 2022)
      The physical magnetospheric cause for geomagnetically induced currents (GICs) are rapid time-varying magnetic fields (dB/dt), which occur mainly during magnetic substorms and storms. When, where and why exactly such rapid ...

    • Effect of ICME-Driven Storms on Field-Aligned and Ionospheric Currents From AMPERE and SuperMAG 

      Pedersen, M.N.; Vanhamäki, H.; Aikio, A.T.; Waters, C.L.; Gjerløv, Jesper; Käki, S.; Workayehu, A.B. (Journal article; Peer reviewed, 2022)
      This study investigates the field-aligned currents (FACs) and ionospheric equivalent currents for interplanetary coronal mass ejection (ICME)-driven storms by considering 45 events with a minimum Dst ≤ −50 nT. The FACs and ...

    • Electrojet Estimates From Mesospheric Magnetic Field Measurements 

      Laundal, Karl Magnus; Yee, J.H.; Merkin, V.G.; Gjerløv, Jesper; Vanhamäki, H.; Reistad, Jone Peter; Madelaire, Michael; Sorathia, K.; Espy, Patrick Joseph (Journal article; Peer reviewed, 2021)
      The auroral electrojet is traditionally measured remotely with magnetometers on ground or in low Earth orbit (LEO). The sparse distribution of measurements, combined with a vertical distance of some 100 km to ground and ...

    • Extreme Event Statistics in Dst, SYM-H, and SMR Geomagnetic Indices 

      Bergin, A.; Chapman, Sandra; Watkins, N.W.; Moloney, N.R.; Gjerløv, Jesper (Journal article; Peer reviewed, 2023)
      Extreme space weather events are rare, and quantifying their likelihood is challenging, often relying on geomagnetic indices obtained from ground-based magnetometer observations that span multiple solar cycles. The Dst ...

    • Field-Aligned and Ionospheric Currents by AMPERE and SuperMAG During HSS/SIR-Driven Storms 

      Pedersen, M.N.; Vanhamäki, H.; Aikio, A.T.; Käki, S.; Workayehu, A.B.; Waters, C.L.; Gjerløv, Jesper (Journal article; Peer reviewed, 2021)
      This study considers 28 geomagnetic storms with Dst $\leq-50$ nT driven by high-speed streams (HSSs) and associated stream interaction regions (SIRs) during 2010-2017. Their impact on ionospheric horizontal and field-aligned ...

    • Global Dynamical Network of the Spatially Correlated Pc2 Wave Response for the 2015 St. Patrick's Day Storm 

      Chaudhry, S.; Chapman, Sandra; Gjerløv, Jesper; Beggan, C. D. (Journal article; Peer reviewed, 2023)
      We show the global dynamics of spatial correlation of Pc2 wave activity can track the evolution of the 2015 St. Patrick's Day geomagnetic storm for an 8 hr time window around onset. The global spatially coherent response ...

    • Global ULF Waves Excited by Solar Wind Dynamic Pressure Impulses: 1. Timescales and Geomagnetic Activity Dependence 

      Xie, Zi-Kang; Zong, Q.G.; Ren, Jie; Yue, Chao; Liu, Zhi-Yang; Liu, Jian-Jun; Hu, Ze-Jun; Li, Xing-Yu; Yin, Ze-Fan; Yan, Yun; Li, Li; Gjerløv, Jesper (Journal article; Peer reviewed, 2023)
      Solar wind dynamic pressure pulse is one of the sources of ultra-low frequency (ULF) waves. Based on 1-second resolution magnetic field observations from SuperMAG from 2012 to 2019, we conducted a statistical study on ...

    • The impact of sunlight on high-latitude equivalent currents 

      Laundal, Karl Magnus; Gjerløv, Jesper; Østgaard, Nikolai; Reistad, Jone Peter; Haaland, Stein; Snekvik, Kristian; Tenfjord, Paul; Ohtani, Shin-ichi; Milan, Steve (Peer reviewed; Journal article, 2016-03)
      Ground magnetic field measurements can be mathematically related to an overhead ionospheric equivalent current. In this study we look in detail at how the global equivalent current, calculated using more than 30 years of ...

    • Interplanetary Magnetic Field Control of Polar Ionospheric Equivalent Current System Modes 

      Shore, R.M; Freeman, MP; Gjerløv, Jesper (Peer reviewed; Journal article, 2019)
      We analyze the response of different ionospheric equivalent current modes to variations in the interplanetary magnetic field (IMF) components By and Bz. Each mode comprises a fixed spatial pattern whose amplitude varies ...

    • Kelvin-Helmholtz Instability Associated With Reconnection and Ultra Low Frequency Waves at the Ground: A Case Study 

      Kronberg, E.A.; Gorman, J.; Nykyri, K.; Smirnov, Artem; Gjerløv, Jesper; Grigorenko, Elena; Kozak, L.V.; Ma, Xuanye; Trattner, K.J.; Friel, M. (Journal article; Peer reviewed, 2021)
      The Kelvin-Helmholtz instability (KHI) and its effects relating to the transfer of energy and mass from the solar wind into the magnetosphere remain an important focus of magnetospheric physics. One such effect is the ...

    • Network analysis of geomagnetic substorms using the SuperMAG database of ground-based magnetometer stations 

      Dods, Joe; Chapman, Sandra; Gjerløv, Jesper (Peer reviewed; Journal article, 2015-09-26)
      The overall morphology and dynamics of magnetospheric substorms is well established in terms of the observed qualitative auroral features seen in ground-based magnetometers. This paper focuses on the quantitative ...

    • Network community structure of substorms using SuperMAG magnetometers 

      Orr, L.; Chapman, S.C.; Gjerløv, Jesper; Guo, W. (Journal article; Peer reviewed, 2021)
      Geomagnetic substorms are a global magnetospheric reconfiguration, during which energy is abruptly transported to the ionosphere. Central to this are the auroral electrojets, large-scale ionospheric currents that are part ...

    • On the Persistent Shape and Coherence of Pulsating Auroral Patches 

      Humberset, Beate Krøvel; Gjerløv, Jesper; Mann, Ian R.; Michell, Robert; Samara, Marilla (Peer reviewed; Journal article, 2018-05)
      The pulsating aurora covers a broad range of fluctuating shapes that are poorly characterized. The purpose of this paper is therefore to provide objective and quantitative measures of the extent to which pulsating auroral ...

    • Scale size-dependent characteristics of the nightside aurora 

      Humberset, Beate Krøvel; Gjerløv, Jesper; Samara, Marilla; Michell, Robert (Peer reviewed; Journal article, 2017-02)
      We have determined the spatiotemporal characteristics of the magnetosphere-ionosphere (M-I) coupling using auroral imaging. Observations at fixed positions for an extended period of time are provided by a ground-based ...

    • Simultaneous Development of Multiple Auroral Substorms: Double Auroral Bulge Formation 

      Ohtani, S.; Gjerløv, Jesper; McWilliams, Kathryn A.; Ruohoniemi, J. M.; Frey, Harald U. (Journal article; Peer reviewed, 2021)
      The expansion phase of auroral substorms is characterized by the formation of an auroral bulge, and it is generally considered that a single bulge forms following each substorm onset. However, we find that occasionally two ...

    • Solar Cycle and Solar Wind Dependence of the Occurrence of Large dB/dt Events at High Latitudes 

      Milan, Stephen Eric; Imber, S.M.; Fleetham, A.L.; Gjerløv, Jesper (Journal article; Peer reviewed, 2023)
      We investigate sharp changes in magnetic field that can produce Geomagnetically Induced Currents (GICs) which damage pipelines and power grids. We use one-minute cadence SuperMAG observations to find the occurrence ...

    • Solar illumination dependence of the auroral electrojet intensity: Interplay between the solar zenith angle and dipole tilt 

      Ohtani, Shinici; Gjerløv, Jesper; Johnsen, Magnar Gullikstad; Yamauchi, Masatoshi; Brändström, Urban; Lewis, Andrew M. (Peer reviewed; Journal article, 2019-08)
      The present study investigates the dependence of the local auroral electrojet (AEJ) intensity on solar illumination by statistically examining northward geomagnetic disturbances in the auroral zone in terms of the solar ...