Climate And Weather of the Sun-Earth System

A new SCOSTEP Program for 2004-2008

Societal Implications of CAWSES

CAWSES and Global Change

Long-term changes in the human habitat, such as surface temperatures or UV exposure have potentially wide-ranging societal, biological and economic impacts. Solar variability (e.g. luminosity changes) can force natural changes in Earth's climate and its protective atmospheric ozone layer, thereby mitigating or enhancing anthropogenic influences on our habitat. Solar changes may also enhance or modify natural variability modes in the coupled climate-atmosphere system (e.g. ENSO). Specifying and understanding the Sun's role in causing surface temperature change, and in modifying ozone can affect policy making about global change. It also impacts seasonal-decadal forecasting. In order to know what environmental changes may be due to human activities, it is necessary to identify those arising from natural causes.

Surface Temperature Change in Arctic Regions since 1600

In "Arctic Environmental Change of the Last Four Centuries", J. Overpeck et al. (Science, v. 278, n. 5341, p. 1251-1256, 1997) compare global Arctic summer-weighted annual surface temperatures inferred from standardized proxy measurements with different possible forcing parameters. Here temperature values are compared with the observed and inferred changes in total solar irradiance (J. Lean et al., Geophysical Research Letters, v. 22, p. 3195, 1995). Prior to 1920, changes in Arctic temperature are likely a result of natural processes. Since about 1920, it may be that accumulation of greenhouse gases resulting from human activities make a significant contribution to producing the higher temperatures.

The figure compares the reconstruction of Northern Hemisphere circum-Arctic temperatures from multiple proxies and inferred variations in solar irradiance (J. Lean et al. 1995). CAWSES should coordinate with existing programs involved with Global Change such as SPARC.

Space Technology and Operations

Aerospace engineers use knowledge of the probable space environment to improve the utilization of space resources and cope with anomalies. Significant economic and societal benefits can result from improved knowledge of the variable space environment in which satellites operate, accurate and timely forecasts of space weather, and coordination of data, models, and information about satellite failures to support post-event analyses.

Rice University Magnetospheric Specification Model and NOAA Geostationary Satellite Anomalies - from D.C. Wilkinson (NOAA-NGDC).

Energetic electrons and ions (plasma) coming from the Sun enter Earth's magnetosphere around the noon sector and move into the magnetotail behind Earth. From collection regions in the magnetotail, they are injected into near-Earth space around the midnight meridian. Electrons drift eastward toward the dawn while oppositely charged protons move toward sunset. Geostationary weather satellites and commercial communications satellites at GEO interact with electrons especially between midnight and dawn as different parts of the surface become highly charged and resulting arcs may affect key components. Computer models such as the Magnetospheric Specification Model of Rice University are used to identify zones of unfavorable operating conditions. A desirable application to be sought by CAWSES is an improvement in recognizing potential solar active regions before they erupt and predicting whether ejected plasma from CMEs will intersect Earth's orbit and affect satellites and astronauts.

Vulnerability of Earth-surface Systems

Society relies on highly technological systems for reliable distribution of electrical power, for radio communications and for navigation on land, at sea, and in the air. All of these are impacted by SES disturbances and vulnerabilities are increasing. Modern power grids are susceptible to induced electric currents from rapidly varying overhead ionospheric currents and their counterparts induced in the conductive Earth, such as can occur from the rapid field changes during large geomagnetic storms. The Global Positioning System (GPS) transmits radio waves that are refracted and slowed by disturbed ionospheric conditions. Significant errors in positioning can result under such conditions. In addition, GPS and satellite communication systems may suffer disruptions due to strong scattering by ionospheric irregularities known as scintillations.

Smoothed Annual Sunspot Number and Geomagnetic Storm Days

A daily measure of geomagnetic disturbance, the Ap index, is available from 1932 to the present. Now it is produced at the GeoForschungs Zentrum, Potsdam, Germany. Ap is derived from the 3-hour Kp index produced for IAGA from magnetogram scalings at a global array of observatories according to a scheme devised in 1949 by J. Bartels. The numbers of days each year having Ap > 40 (when there is a significant magnetic storm in progress) are shown in red against the backdrop of the smoothed annual sunspot numbers. It is obvious that the distribution of magnetic storms at Earth is more complex than the pattern of high and low sunspots. Large magnetic storms disrupt telecommunications, cause power system failures, and may cause a variety of satellite anomalies.

Humans in space

Bursts of energetic solar particles can harm humans in space. Astronauts involved in extra vehicular activity (EVA) outside a space station or a shuttle in high inclination orbit are especially vulnerable, as are those in deep space, on the Moon, or in a spacecraft, especially around the time of the maximum in the 11-year solar cycle. Passengers and crew on high altitude aircraft on polar routes, e.g. supersonic airplanes, are susceptible to radiation hazards during space storm events.

Computer Upsets on Shuttle Missions: STS-37, -39, -43, and -44 -- Daniel C. Wilkinson (NOAA)

Anomalies in Low-Earth Orbit (LEO) may happen anywhere in space through which the Shuttle passes. However, these recorded computer "hits" appear to be concentrated in the South Atlantic Anomaly (SAA) region and high-latitude auroral zones. Because Earth's internal dipole is offset from its center toward the Pacific, it creates a weaker magnetic shield above the Atlantic off the coast of Brazil. The downward curving geomagnetic field lines connecting with the upper atmosphere over the polar regions provides a focus mechanism to direct charged particles down into the N. and S. auroral zones. Typically, Shuttle flights do not reach high latitudes, although during high solar activity and geomagnetic storms the auroral zone expands and can impact humans in space and their equipment, as well as simple.

CAWSES Office, Center for Space Physics, Boston University, 725 Commonwealth Ave. Boston, MA 02215 USA; Phone: 617/353-5990; FAX: 617/353-6463;