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ISR Space Weather Project

solar and interplanetary research and instrument development relevant to space weather

Earth in the Solar Wind

ISR personnel have worked for many years in collaboration with several government agencies, including the Air Force Research Laboratory (AFRL), NASA and the Navy, on programs involving solar-terrestrial research and heliospheric imager instrument development, data processing and data analysis. Our goals are to understand the origins and interplanetary (IP) propagation of disturbances that affect the geosphere, to support data processing and analyses from AFRL spacecraft missions such as the Solar Mass Ejection Imager (SMEI) and the Communication / Navigation Outage Forecasting System (C/NOFS) mission, and to help develop next-generation heliospheric imagers. The research utilizes many spacecraft and ground-based observations of solar, IP and geomagnetic phenomena and observations from the SMEI, STEREO Heliospheric Imagers (HIs) and other current and future imaging experiments.

A major portion of this work involves research using these data sets to address three scientific topics of current importance:

- The solar eruptive phenomena which lead to sporadic geomagnetic storms; 
- Shock waves and other IP signatures of solar ejecta; 
- The characteristics of IP disturbances which produce geomagnetic storms.

The most important goal of the studies is to utilize data sets related to solar ejecta and their IP manifestations to define the origins, geometry and propagation characteristics of geoeffective disturbances.  Boston College ISR personnel have been at the forefront of such studies and, therefore, have been instrumental in supporting our government’s space weather programs.

Figure 1: SOHO LASCO C2 image showing detail in solar ejecta

Coronal mass ejections (CMEs – see Webb and Howard, 2012 for a review) and their associated phenomena are the key drivers of major space weather at Earth and throughout the heliosphere. Figure 1 shows a SOHO LASCO C2 image from 4 January 2002 of a CME showing detail in the ejected material. The solar limb Sun is represented by the white circle. Major CMEs inject large amounts of mass and magnetic fields into the heliosphere and, when aimed Earthward, can cause major geomagnetic storms and drive IP shocks, a key source of solar energetic particles. CMEs exhibit variable speeds, intensities and trajectories.

Figure 2: CME appearance from three different angles

Figure 2 shows images of the same event (an Earth-directed CME in early April 2010) observed from three different viewpoints. The center (b) shows the perspective from SOHO LASCO along the Sun-Earth line where the CME appears as a halo. (A) and (c) show the same CME as observed by each STEREO spacecraft, separated in longitude by ~70° from LASCO at this time. The event appears in each COR-2 image as a limb CME directed towards the left (right) relative to STEREO-A (-B). The dramatic change in the appearance of the CME, with the only physical change being the viewing location, demonstrates the importance of perspective with respect to measuring CME properties and tracking its direction.

Currently, predicting when a CME will be launched from the Sun is very uncertain, and to better forecast and mitigate their effects it is necessary to detect and track CMEs from near the Sun to Earth with a heliospheric imager/detector. Without such monitoring, forecasters are blind to CMEs for 85% of the Sun-Earth distance and, thus, unable to accurately predict the time of arrival and trajectory of a CME, or the intensity and duration of the consequent geomagnetic storm. 

Studies with SMEI and STEREO have proven that a heliospheric imager in Earth orbit and/or at suitable locations in space can provide early warning of ~1-3 days of Earth arrival of CMEs, the driver of major storms. AFRL, NASA and the Navy are involved in efforts to develop next-generation heliospheric imagers with the goal of providing an operational forecast system. ISR personnel support and analyze the data returned from the SMEI and STEREO HI experiments, and are supporting the development of next-generation imager experiments.

Select Publications:

Webb, D. and Howard, T. 2012, "Coronal Mass Ejections: Observations", Living Rev. Solar Phys. 9 (2012), 3. Link.

Point of Contact for this project is David F. Webb.