Hiromitsu Ishibashi

The 17 March 2015 storm: the associated magnetic flux rope structure and the storm development

The objective of this study is (1) to determine the magnetic cloud (MC) structure associated with the 17 March 2015 storm and (2) to gain an insight into how the storm developed responding to the solar wind conditions. First, we search MC geometries which can explain the observed solar wind magnetic fields by fitting to both cylindrical and toroidal flux rope models. Then, we examine how the resultant MC geometries can be connected to the solar source region to find out the most plausible model for the observed MC. We conclude that the observations are most consistently explained by a toroidal flux rope with the torus plane nearly parallel to the ecliptic plane. It is emphasized that the observations are characterized by the peculiar spacecraft crossing through the MC, in that the magnetic fields to be observed are southward throughout the passage. For understanding of the storm development, we first estimate the injection rate of the storm ring current from the observed Dst variation. Then, we derive an expression to calculate the estimated injection rate from the observed solar wind variations. The point of the method is to evaluate the injection rate by the convolution of the dawn-to-dusk electric field in the solar wind and a response function. By using the optimum response function thus determined, we obtain a modeled Dst variation from the solar wind data, which is in good agreement with the observed Dst variation. The agreement supports the validity of our method to derive an expression for the ring current injection rate as a function of the solar wind variation.Graphical abstract.

Operation of a Data Acquisition, Transfer, and Storage System for the Global Space-Weather Observation Network

A system to optimize the management of global space-weather observation networks has been developed by the National Institute of Information and Communications Technology (NICT). Named the WONM (Wide-area Observation Network Monitoring) system, it enables data acquisition, transfer, and storage through connection to the NICT Science Cloud, and has been supplied to observatories for supporting space-weather forecast and research. This system provides us with easier management of data collection than our previously employed systems by means of autonomous system recovery, periodical state monitoring, and dynamic warning procedures. Operation of the WONM system is introduced in this report.