Characteristics of magnetospheric energetics during geomagnetic storms

Abstract

[1] To investigate the magnetospheric energetics during magnetic storms, we performed a statistical survey of 307 geomagnetic storms between 1995 and 2009. For the purpose of getting a detailed understanding of the energy processes, we conducted our study of storm-time energetics for three time durations: the main phase, the recovery phase, and the total storm period. We found that the partition of the energy dissipation via the ring current injection and high-latitude ionospheric dissipation is controlled by the storm intensity. The proportion of the ring current injection increases linearly as the storm intensity increases for all three time durations. For moderate storms, the high-latitude ionospheric dissipation is dominant, with only $30% energy dissipated via the ring current; whereas for superstorms, the ring current injection becomes dominant, with $70% energy dissipated via the ring current. We also confirmed the essential and crucial role of the total energy input into the magnetosphere during the main phase in controlling the storm intensity. The total energy input during the main phase is directly proportional to the storm intensity. Their correlation efficiency is as high as 0.85. The storm-time energy budget was also quantified in this study. The coupling efficiency indicates an exponential decay as the storm intensity increases, with the coupling efficiency during the main phase less than that during the recovery phase.

Variation of Solar Wind Parameters Along With the Understanding of Energy Dynamics Within the Magnetospheric System During Geomagnetic Disturbances

“…There is yet no concrete result to confirm that the geomagnetic activity strictly enhances or depletes during the initial phase of the storm as many authors have diverse results (Abdu et al, 1991;Adeniyi, 1986;Lakshmi et al, 1991). Considering the percentage of energy sink composition our result is in coherence with the result of Li et al (2012), where ring current contributed 34.7% but they considered the storm with Dst ≤ −50 nT. The storm after initial phase goes through main phase characterized by the strong depression in SYM-H from the weaker value of −5 to −122 nT in the late evening of 29 May.…”

“…According to the work of Li et al (2012), the energy injection rate depends upon the strength of the storm and for moderate storm normally, the composition of energy sink in ionosphere is more dominant giving only about 30% of the total deposited energy to the ring current injection. Substorm releases the stored magentospheric energy bringing different changes in the magnetosphere such as variation of ground magnetic field, auroral activity, and the magnetospheric plasma and field properties and, respectively, referred as "polar magnetic substorm," "auroralsubstorm," and "magnetic substorm."…”

Ionosphere-thermosphere (IT) response to solar wind forcing during magnetic storms

“…Over many years of research into the effects of solar wind forcing on the ionosphere-thermosphere (IT) system, it has been generally assumed that energy enters and dissipates in the auroral zones and ring current (Akasofu 1981;Weiss et al 1992; Knipp et al 1998;Li et al 2012, and references therein). This assumption is based on the effect of particle precipitation which gives rise to intense auroral emissions and high conductivity in the auroral zone (Evans et al 1977;Vondrak & Robinson 1985;Fuller-Rowell & Evans 1987;Coumans et al 2004, and many others).…”

Where does Earth’s atmosphere get its energy?

“…Numerous studies have estimated the power dissipation in magnetic storms (e.g., Akasofu 1978;Stern 1984;Akasofu & Kamide 1985;Weiss et al 1992;Lu et al 1995;Knipp et al 1998;Lu et al 1998;Baker et al 1997;Silbergleit et al 1997;Baker et al 2001;Pulkkinen et al 2002;Tanskanen et al 2002;Feldstein et al 2003;Palmroth et al 2004;Tanskanen et al 2005;Alex et al 2006;Guo et al 2011;Li et al 2012;Akasofu 2013). There is a wide range in dissipative energies due to the varying strength of the solar wind and geomagnetic indices, storm duration, as well as the technique used to derive the global power.…”

“…The partitioning of the magnetic storm dissipation energy can be estimated using multiple techniques including ground and satellite-based observations of energy fluxes, empirical formulas (e.g., Pulkkinen et al 2002;Li et al 2012), model simulations (Palmroth et al 2004;Tanskanen et al 2005;Ngwira et al 2013), and assimilation techniques . In empirical methods, for example, estimates of the solar wind input energy, a function of solar wind speed and solar magnetic field orientation and strength (Silbergleit et al 1997) is used to determine the energy input into the magnetosphere (Gonzalez et al 1994;Pulkkinen et al 2002).…”