Statistical analysis of the geomagnetic response to different solar wind drivers and the dependence on storm intensity

Abstract

Geomagnetic storms start with activity on the Sun that causes propagation of magnetized plasma structures in the solar wind. The type of solar activity is used to classify the plasma structures as being either interplanetary coronal mass ejection (ICME) or corotating interaction region (CIR) driven. The ICME-driven events are further classified as either magnetic cloud (MC) driven or sheath (SH) driven by the geoeffective structure responsible for the peak of the storm. The geoeffective solar wind flow then interacts with the magnetosphere producing a disturbance in near-Earth space. It is commonly believed that a SH-driven event behaves more like a CIR-driven event than a MC-driven event; however, in our analysis this is not the case. In this study, geomagnetic storms are investigated statistically with respect to the solar wind driver and the intensity of the events. We use the Hot Electron and Ion Drift Integrator (HEIDI) model to simulate the inner magnetospheric hot ion population during all of the storms classified as intense (Dst min ≤ À100 nT) within solar cycle 23 (1996-2005). HEIDI is configured four different ways using either the Volland-Stern or self-consistent electric field and either event-based Los Alamos National Laboratory (LANL) magnetospheric plasma analyzer (MPA) data or a reanalyzed lower resolution version of the data that provides spatial resolution. Presenting the simulation results, geomagnetic data, and solar wind data along a normalized epoch timeline shows the average behavior throughout a typical storm of each classification. The error along the epoch timeline for each HEIDI configuration is used to rate the model's performance. We also subgrouped the storms based on the magnitude of the minimum Dst. We found that typically the LANL MPA data provide the best outer boundary condition. Additionally, the self-consistent electric field better reproduces SH-and MC-driven events throughout most of the storm timeline, but the Volland-Stern electric field better reproduces CIR-driven events. Contrary to what we expect, examination of the HEIDI model results and solar wind data shows that SH-driven events behave more like MC-driven events than CIR-driven storms.

Space Weather Effects Produced by the Ring Current Particles

“…This perturbation can be considered as a rough equivalent to the Dst-index if it is assumed (Carovillano and Siscoe 1973) that it is close to the perturbation averaged around the equator of the Earth. The DPS relation was used in numerous studies for Dst-index estimates from modeling and observations and related ring current dynamics (e.g., Greenspan and Hamilton 2000;Ebihara and Ejiri 2000;Fok et al 2001b;Jordanova et al 2012;Ganushkina et al 2012;Katus et al 2015;Zhao et al 2015). However, the Dst-index contains contributions from many other sources than the azimuthally symmetric ring current and their contributions can be significant or even largest during disturbed conditions.…”

Dynamics of large‐scale solar wind streams obtained by the double superposed epoch analysis

“…Only disturbed types of SW streams can contain the IMF component perpendicular to the ecliptic plane and in particular the southward IMF component. Such disturbed types are the following SW streams: interplanetary manifestation of coronal mass ejection (ICME) including magnetic cloud (MC) and Ejecta, Sheath-compression region before ICME and corotating interaction region (CIR)-compression region before high-speed stream (HSS) of solar wind (see reviews and recent papers by Gonzalez et al [1999], Huttunen and Koskinen [2004], Yermolaev [2006, 2010], Zhang et al [2007], Yermolaev et al [2012], Hietala et al [2014], Cid et al [2014], Katus et al [2015], and references therein). In the mentioned above works the SW types are considered as sources of magnetospheric disturbance, i.e., the selection of SW events is carried out in connection with magnetospheric activity.…”

The effect of ring current electron scattering rates on magnetosphere‐ionosphere coupling

“…In this study, the results are compared to the D s t ∗ index from both the Kyoto World Data Center and the United States Geological Survey (USGS) [ Love and Gannon , ; Gannon and Love , ]. The D s t ∗ index more accurately describes the storm time ring current by removing from the D s t index the contributions from the magnetopause current, induced currents in the conducting Earth, and the quiet time ring current [ Ebihara and Ejiri , ; Kozyra et al , ; Liemohn et al , ; Katus et al , ]. The model calculates D s t ∗ using the Dessler‐Parker‐Sckopke relationship [ Dessler and Parker , ; Sckopke , ] given by where E R C is the total modeled ring current energy in KeV and D s t ∗ is in nanotesla.…”

“…The model is such that the loss rate, , transitions from strong to weak pitch angle diffusion by where τ is the lifetime against strong diffusion, φ is the MLT, and λ is the scattering rate as a function of MLT ( φ ), energy (E), and geocentric distance (R) [ Chen et al , ]. Note that this relationship does not include a dependence on magnetic activity, which can change the location of the plasmapause [ Moldwin et al , ; Katus et al , ] and scattering from enhanced wave amplitudes [ Meredith et al , ; Miyoshi et al , ].…”