Title: Solar Variability and its effects on the Earth's Environment
Author: P. Brekke
Affil: ESA Space Science Department
Email: pbrekke@esa.nascom.nasa.gov
Abstract: Transient variations in the particle and EUV flux from the Sun causes disturbances in the Earth's space environment affecting some of the technologies that we depend on both in orbit and on the ground. Both, the increasing deployment of radiation-, current-, and field-sensitive technological systems over the last few decades and the increasing presence of complex systems in space, combine to make society more vulnerable to solar-terrestrial disturbances. Thus, today our society is much more sensitive to space weather activity than it was during the last solar maximum. The Solar and Heliospheric Observatory (SOHO) has obtained significant new information about coronal mass ejections (CMEs), the source of the most severe disturbances in the Earth's environment. By observing the Sun 24 hours a day, SOHO has proved to be an important ``space weather watchdog''. The importance of real-time monitoring of the Sun will be pointed out and a number of enterprises affected by space weather will be discussed.
Title: The Effect of Solar Proton Events on Ozone and Other Constituents in the Middle Atmosphere
Author: Charles H. Jackman
Affil: Code 916, NASA Goddard Space Flight Center, Greenbelt, MD, 20771
Email: jackman@assess.gsfc.nasa.gov
Authors: Richard D. McPeters
, Gordon J. Labow
, Eric L. Fleming,
James M. Russell
, and Cid J. Praderas
Affils: NASA Goddard Space Flight Center,
Science Systems and Applications, Inc.,
Hampton University,
Emergent Information Technologies, Inc.
Abstract: Solar proton events (SPEs) can result in increases in both HO
(H, OH, HO
) and NO (N, NO, NO) constituents in the
middle atmosphere polar region (> 60 degrees geomagnetic). HO
constituents produced by SPEs caused decreases in mesospheric and upper
stratospheric ozone observed during several events. Recent SPEs in
July and November of 2000 caused ozone decreases of over 30% during
the event as measured by UARS HALOE and NOAA 14 SBUV/2.
These HO-driven ozone depletions last only during the SPEs
(several hours to a few days) because of the short lifetimes of
HO constituents in the atmosphere. The NO species feed into
the entire odd nitrogen family NO
(N, NO, NO,
NO
, NO
, HNO, HNO
, ClONO, BrONO)
over a period of hours to weeks. The NO family lasts several months
or more in the stratosphere with low sun conditions. The two
largest SPEs in the past thirty years, October 1989 and August 1972,
caused polar stratospheric ozone depletions >10% for weeks past the
events. The SPE in July 2000, third largest in thirty years, was
measured by NOAA 14 SBUV/2 to decrease ozone by several percent
for days past the event. Enhancements in mesospheric NO of over
50 ppbv were also measured by UARS HALOE during this event. A review
of the influence of SPEs on ozone and other constituents in the middle
atmosphere will be given in this talk.
Title: Impact on Earth's Upper Atmosphere of EUV and Solar X-rays, and Implications for Space Weather
Author: Tim Fuller-Rowell
Affil: Space Environment Center
Email: tim.fuller-rowell@noaa.gov
Abstract: Solar extreme ultraviolet (EUV) radiation (10-100nm) is the main source of energy and ionization of the upper atmosphere. Variation of EUV over the solar cycle gives rise to large changes in neutral and ionospheric density, total electron content (TEC), and low-latitude plasma irregularities. Implications for space weather include: increased drag on low-altitude Earth-orbiting satellites, disruption of high-frequency (HF) radio communication, positioning errors in single frequency GPS navigation, and scintillation of satellite communication signals. Solar soft X-rays (1-10nm) are a source of the E-region ionosphere and produce of NO in the lower thermosphere. Recent measurements of the flux of soft X-rays by SNOE have resolved discrepancies in the E-region electron density profile, but some NO production issues remain. The flux at harder X-ray wavelengths (0.1-0.8nm) are highly variable, and can increase by three orders of magnitude during a solar flares. During these events, D-region ion density increases following the time history of the flare, and causes absorption of HF radio signals and disruption of low frequency navigation systems.