Copyright © National Academy of Sciences. All rights reserved.
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS
181
component of this unexplored frontier and provides a natural means of probing the coupling mechanisms
that redistribute solar and magnetospheric energy at Earth. Determining how redistribution of precipitating
particle energy influences atmospheric composition and structure, and how nonlinear coupling processes
amplify these impacts beyond those expected from the absolute energy input, would represent a fundamental advance in heliophysics.
Coupling of different regions via radiative, dynamical, and chemical feedbacks controls weather and
climate throughout the atmosphere. Through these feedback processes the remote regions highly driven by
solar influences are linked to the troposphere where human activities are concentrated. Yet how solar and
magnetospheric variability affects atmospheric conditions and climate in such an interconnected system
remains an open question. Only with a deeper understanding of the natural variability, and of the way
external influences perturb the coupling processes, will researchers be able to model this complex system
and thereby develop a predictive capability for future generations.
EPP refers to energetic electrons and protons impinging on Earth’s atmosphere after they have been
accelerated by solar and magnetospheric activity. Figure 8.5 in the section above titled “Significant
Accomplishments of the Previous Decade” depicts current, incomplete understanding of the atmospheric
response to EPP. Solar magnetic variability produces changes both in irradiance and in the plasmas and
magnetic fields that permeate interplanetary space, driving space weather at Earth. The resulting EPP occurs
at all times during the solar cycle but has different characteristics depending on particle sources, which
are broadly associated with different geomagnetic activity levels. Through ionization and dissociation EPP
produces NO and NO 2 , collectively referred to as NO x , the primary catalytic destroyer of ozone (O 3 ) in
most of the stratosphere. NO x produced by EPP (EPP-NO x ) can be created directly in the stratosphere by
high-energy particles, or in the mesosphere and lower thermosphere (MLT) by lower-energy particles. EPPNO x descends from the MLT into the stratosphere during the polar winter (see Figure 8.19, for example).
The downward transport is controlled by an unknown combination of diffusion, large-scale circulation,
and confinement in the polar vortex, with winds and waves modifying these elements.
NO x is an atmospheric coupling agent because of its impact on O 3 , either through the NO x catalytic
loss cycle, or by interfering with other catalytic O 3 loss cycles. Changes in O 3 can alter temperature
gradients, and thereby influence circulation. Perturbations to these three entities are intertwined and can
trigger nonlocal changes, e.g., by perturbing propagation of waves to the upper atmosphere or weather
and climate in the lower atmosphere. Thus EPP-NO x -induced perturbations in O 3 are communicated via
effects on temperature and circulation upward to the MLT and potentially downward to the troposphere,
thereby triggering the redistribution of particle energy throughout the atmosphere. These results suggest a
mechanism for EPP indirectly affecting even tropospheric climate, evidence for which is provocative but
tenuous. Tropospheric perturbations themselves—either natural or human-induced—can be communicated
to the middle and upper atmosphere, thereby altering the atmospheric response to EPP. The coupling pathways described here form a critical yet poorly understood link between heliophysical forcing and Earth’s
climate system. A complete description of the Sun-Earth system requires understanding of the pathways
by which EPP transmits signals of solar magnetic variability through Earth’s atmosphere, specifically the
amplifying coupling processes triggered by EPP-NOx. It is then important to ask: How do EPP-initiated
chemical changes translate to thermal and dynamical changes throughout the atmosphere?
The AIMI panel concluded that a major goal for the upcoming decade is to determine how our planetary
environment is changing over multi-decadal scales, and to understand how the changes are embodied in
or transmitted through the AIM system.
This goal triggers two major implications. First, long-term observations that provide the best information about the degree of change, and that best serve to constrain models, must be protected if scientists
are to understand and predict long-term change in the AIM system. Second, fundamental processes and
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS
181
component of this unexplored frontier and provides a natural means of probing the coupling mechanisms
that redistribute solar and magnetospheric energy at Earth. Determining how redistribution of precipitating
particle energy influences atmospheric composition and structure, and how nonlinear coupling processes
amplify these impacts beyond those expected from the absolute energy input, would represent a fundamental advance in heliophysics.
Coupling of different regions via radiative, dynamical, and chemical feedbacks controls weather and
climate throughout the atmosphere. Through these feedback processes the remote regions highly driven by
solar influences are linked to the troposphere where human activities are concentrated. Yet how solar and
magnetospheric variability affects atmospheric conditions and climate in such an interconnected system
remains an open question. Only with a deeper understanding of the natural variability, and of the way
external influences perturb the coupling processes, will researchers be able to model this complex system
and thereby develop a predictive capability for future generations.
EPP refers to energetic electrons and protons impinging on Earth’s atmosphere after they have been
accelerated by solar and magnetospheric activity. Figure 8.5 in the section above titled “Significant
Accomplishments of the Previous Decade” depicts current, incomplete understanding of the atmospheric
response to EPP. Solar magnetic variability produces changes both in irradiance and in the plasmas and
magnetic fields that permeate interplanetary space, driving space weather at Earth. The resulting EPP occurs
at all times during the solar cycle but has different characteristics depending on particle sources, which
are broadly associated with different geomagnetic activity levels. Through ionization and dissociation EPP
produces NO and NO 2 , collectively referred to as NO x , the primary catalytic destroyer of ozone (O 3 ) in
most of the stratosphere. NO x produced by EPP (EPP-NO x ) can be created directly in the stratosphere by
high-energy particles, or in the mesosphere and lower thermosphere (MLT) by lower-energy particles. EPPNO x descends from the MLT into the stratosphere during the polar winter (see Figure 8.19, for example).
The downward transport is controlled by an unknown combination of diffusion, large-scale circulation,
and confinement in the polar vortex, with winds and waves modifying these elements.
NO x is an atmospheric coupling agent because of its impact on O 3 , either through the NO x catalytic
loss cycle, or by interfering with other catalytic O 3 loss cycles. Changes in O 3 can alter temperature
gradients, and thereby influence circulation. Perturbations to these three entities are intertwined and can
trigger nonlocal changes, e.g., by perturbing propagation of waves to the upper atmosphere or weather
and climate in the lower atmosphere. Thus EPP-NO x -induced perturbations in O 3 are communicated via
effects on temperature and circulation upward to the MLT and potentially downward to the troposphere,
thereby triggering the redistribution of particle energy throughout the atmosphere. These results suggest a
mechanism for EPP indirectly affecting even tropospheric climate, evidence for which is provocative but
tenuous. Tropospheric perturbations themselves—either natural or human-induced—can be communicated
to the middle and upper atmosphere, thereby altering the atmospheric response to EPP. The coupling pathways described here form a critical yet poorly understood link between heliophysical forcing and Earth’s
climate system. A complete description of the Sun-Earth system requires understanding of the pathways
by which EPP transmits signals of solar magnetic variability through Earth’s atmosphere, specifically the
amplifying coupling processes triggered by EPP-NOx. It is then important to ask: How do EPP-initiated
chemical changes translate to thermal and dynamical changes throughout the atmosphere?
The AIMI panel concluded that a major goal for the upcoming decade is to determine how our planetary
environment is changing over multi-decadal scales, and to understand how the changes are embodied in
or transmitted through the AIM system.
This goal triggers two major implications. First, long-term observations that provide the best information about the degree of change, and that best serve to constrain models, must be protected if scientists
are to understand and predict long-term change in the AIM system. Second, fundamental processes and