Exploring Storm Time Ring Current Formation and Response on the Energy Input.

Abstract

While extensive research has been made over the last decades regarding the storm-time dynamics, there are still unanswered questions regarding the ring current formation and plasmasphere evolution, specifically about the ring current response on the energy input. Large-scale data analysis and global magnetospheric simulations provide complementary alternatives for exploring highly complex coupling of the solar wind-ionosphere-magnetosphere system.

Superposed Epoch analysis of intense storms data suggests that a distinct time stamp is needed in order to resolve certain solar wind features. However, when it comes to hot proton at geosynchronous orbit, the choice of reference time primarily matters to accurately describe the size of peaks, while the presence and time evolution is unaltered by it.

Examination of the role the transient spikes in the solar wind parameters play in the development of magnetic storms, reveals that changes in the energy input produce a nonlinear response of the inner magnetosphere. While initial increases in the energy input enhance the magnetospheric response, as the power transferred to the system is increased, the growth of the ring current is stalled and a saturation limits sets in. A threshold in the energy input is necessary for the ring current to develop, while the short time scale fluctuations in the solar wind parameters did not have a significant contribution. This implies the existence of an internal feedback mechanism as the magnetosphere acts as a low-pass filter of the IMF, limiting the energy flow in the magnetosphere.

Further, the main characteristic in determining IMF Bz fluctuation periodicity transfer of solar wind mass and energy to the inner magnetosphere, is the peak signal to noise ratio in the power spectrum of the input parameter, suggesting that a ratio of 10 is needed in order to trigger a similar periodicity in the magnetosphere response.

Theoretical and numerical modifications to an inner magnetosphere model (HEIDI) were implemented, accommodating for a non-dipolar arbitrary magnetic field. With HEIDI fully incorporated into the SWMF, an examination of model sophistication on our scientific findings can be explored. Initial simulations have been conducted and the results are discussed.