SWEETS

Starting point / motivation

The term "space weather" deals with the dynamic conditions in the Earth's outer space environment including physical processes on the Sun. The strongest disturbances of the space environment are primarily caused by coronal mass ejections (CMEs).

CMEs are huge clouds of magnetized plasma and may lead to perturbations of electronic devices. If the CME is Earth-directed, it may result in severe disruptions of the technical infrastructure on Earth and in space (satellites). CMEs can interrupt navigation and communication services or even be the trigger for the loss of complete electricity grids (Quebec 1989, Malmö 2003). In today's modern society, with steadily increasing technology, it is of utmost importance to recognize and face up to the space weather threat.

Contents and goals

Hence, the goal of the project SWEETS is to make a sustainable contribution to the subject of space weather. For this reason, it is proposed to develop a forecasting model in order to estimate the expected impact of CMEs on satellites, which is highly relevant for satellite operators (LOI). Based on this study the tool shall be applied in the ESA space situational awareness (SSA) program.

Due to the extensive knowledge of the Institute of Geodesy in the field of kinematic orbit determination, the unique possibility arises to estimate solar storm induced density variations. So far, the influence of extreme solar events on the atmosphere is almost exclusively estimated based on accelerometer observations of single satellite missions (CHAMP, GRACE). However, at the time of writing, only one satellite mission (GRACE-FO) equipped with suitable accelerometers is orbiting the Earth.

Hence, within the project SWEETS, a combined analysis based on a wide variety of satellites (e.g. SWARM A-C, TerraSAR-X, Tandem-X, CHAMP, GRACE, GRACE-FO, Cryosat-2, Sentinel 1-2, ...) shall be realized for the first time.

Methods

The analysis will be based on neutral mass densities deduced from kinematic orbit information and, if existing, in-situ measurements of on-board accelerometer. Since all these satellites are orbiting at different altitudes between 300-800km, a tomography of the upper Earth's atmosphere is feasible and the impact of a solar event on a satellite can be estimated as a function of its orbital altitude.

The basis on which the forecasting model will estimate the expected influences, are real-time measurements of solar wind plasma and magnetic field data from satellites at the Lagrange point L1 (ACE, Wind, DSCOVR). Because of the distance between the Lagrange point L1 and the Earth (1.5 million kilometres) we can estimate incoming, and for satellites potentially hazardous, thermospheric density increases with an average lead time of 45 minutes – depending on the velocity of the CME. For the support and temporal expansion of the forecast, to approximately 2 hours, predictions of geomagnetic and solar indices will be additionally incorporated.

Expected results

For the analysis and evaluation of the several hundred CMEs since 2000 a semi-automatic algorithm will be developed. The estimation of local/relative maxima or minima and the elaboration of various gradients (impulsive versus gradual variations) will additionally provide information about the structure (shock-sheath, magnetic structure) of the individual CMEs.

To store the resulting data a solar event database will be set up, which also serves as a basis for the forecasting model. The results elaborated during the project will be openly available to the public and other research areas by means of a real-time demonstrator.

Coordinator

Graz University of Technology

Project partner

University of Graz

Graz University of Technology
Rechbauerstraße 12
A-8010 Graz
Web: www.tugraz.at