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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2000

Satellite Measured Solar Protons from 1963-1993 and Their Influence on Ozone in a Changing Stratosphere

The fluxes of solar protons have been measured by a series of Interplanetary Monitoring Platform (IMP) satellites since 1963. Eight IMP satellites have been launched since 1963 providing excellent coverage of solar protons with energies from a few MeV to several hundred MeV. IMP 8, launched in October 1973, continues to provide proton measurements, twenty-six and a half (26 1/2) years after launch. These high energy solar protons rain down on the earth's polar atmosphere sporadically, primarily during solar proton events (SPEs) which typically last a few days. Solar protons with energies of 30 MeV or greater are capable of reaching the stratosphere and causing increases in odd nitrogen (NO(y)) constituents at polar latitudes ($>$ 60 degrees geomagnetic) which last for several months to years past the events. These enhanced NO(y) species can lead to significant upper stratospheric ozone depletions $ greater than $10\% during the gigantic SPEs that occurred in August 1972 and October 1989. We studied the effects of SPEs on the stratosphere from 1963 to the mid 1990s. During this time period, the stratospheric chlorine levels changed from relatively small in 1963 ($\sim$ 1 ppbv) to fairly substantial amounts in the mid-1990s ($\sim$ 3.3 ppbv). Our recently improved two-dimensional chemistry and transport atmospheric model was used to compute the effects of SPEs in this changing stratosphere. The long-lived SPE-produced NO(y) constituents were transported to lower stratospheric levels during winter after the events and caused impacts in the middle and lower stratosphere. Generally, the SPEs resulted in a decrease in ozone. However, during periods of high halogen loading these impacts resulted in interference with the chlorine and bromine loss cycles for ozone destruction. This interference actually led to a predicted total ozone increase that was especially notable in the time period 1992-4, a few years after the October 1989 SPE.

Jackman, Charles H.↗
NASA NTRS2012

The Influence of Large Solar Proton Events on the Atmosphere

Solar proton events (SPEs) can cause changes in constituents in the Earth s polar middle atmosphere. A number of large SPEs have occurred over the past 50 years and tend to happen most frequently near solar maximum. The highly energetic protons cause ionizations, excitations, dissociations, and dissociative ionizations of the background constituents. Complicated ion chemistry leads to HOx (H, OH, HO2) production and dissociation of N2 leads to NOy (N, NO, NO2, NO3, N2O5, HNO3, HO2NO2, ClONO2, BrONO2) production. Both the HOx and NOy increases can result in changes to ozone in the stratosphere and mesosphere. The HOx increases lead to short-lived (~days) ozone decreases in the mesosphere and upper stratosphere. The NOy increases lead to long-lived (~several months) stratospheric ozone changes because of the long lifetime of NOy constituents in this region. UARS HALogen Occultation Experiment (HALOE) instrument observations showed SPE-caused polar stratospheric NOx (NO+NO2) increases over 10 ppbv in September 2000 due to the very large SPE of July 2000, which are reasonably well simulated with the Whole Atmosphere Community Climate Model (WACCM). WACCM-computed SPE-caused polar stratospheric ozone decreases >10% continued for up to 5 months past the largest events in the past 50 years, however, SPE-caused total ozone changes were not found to be statistically significant. Small polar middle atmospheric temperature changes of <4 K have also been predicted to occur as a result of the larger SPEs. The polar atmospheric effects of large SPEs during solar cycle 23 and 24 will be emphasized in this presentation.

Jackman, Charles H.↗
NASA NTRS1973

Access of solar protons to the earth's polar caps.

Energetic solar proton observations in the interplanetary medium by Explorer 33 and Explorer 35 and over the polar caps by Injun 5 during the period from September 1968 through March 1970 have been examined in detail. The solar proton intensities observed over the polar regions were compared with the interplanetary intensities on an absolute basis. The high polar latitude (HPL) proton intensities tracked the magnetic field aligned interplanetary intensities well (solar-antisolar intensities as determined from the sectored Explorer data). The tracking was in agreement with the open magnetosphere model about 90% of the time - i.e., the intensities observed on the HPL magnetic lines of force, which would be connected to magnetic lines of force from the sun in an interconnected geomagnetic and interplanetary magnetic field, were in agreement with the maximum intensity of the interplanetary proton pitch angle distribution. The intensities observed at the HPL region of the opposite polar cap were in agreement with the minimum intensity of the interplanetary pitch angle distribution. The low polar latitude intensities generally tracked the maximum interplanetary intensity very well.

Fennell, J. F.↗
NASA NTRS2005

Recent Solar-Proton Fluxes

The event-integrated fluences of energetic solar protons up to 2004 at the Earth have been determined and compared to previous data. The current solar cycle has been very active, and very large fluxes of solar protons have been observed that have had serious effects in the solar system and will have produced many radionuclides in the surfaces of meteorites. Such huge events are not expected again until about 2008 or 2009.

Reedy, R. C.↗
NASA NTRS2007

Long-Term Atmospheric Changes Caused by the Very Large Solar Proton Event in July 2000

Solar cycle 23 was accompanied by eight very large solar proton events (SPEs) between 2000 and 2005, along with numerous smaller events. The very large SPE in July 2000, which was associated with the well-known 'Bastille Day Solar Storm,' caused very substantial changes in the polar mesosphere and stratosphere. Significant downward transport of the SPE-produced NO(x) from the polar lower mesosphere and upper stratosphere during the Southern Hemisphere winter period resulted in huge enhancements (>100%) in middle stratospheric NO(x) (NO+NO2) during September 2000 in the polar vortex, which were measured by UARS HALOE (C. E. Randall et al., Geophys. Res. Lett., 28,2385-2388,2001). We have used the Whole Atmosphere Community Climate Model (WACCM) to study the longer-term impact of the July 2000 SPE, the third largest SPE period in the past 40 years. This very large SPE provided a wonderful opportunity to study the downward transport of energetic particle precipitation effects in the middle atmosphere. Not surprisingly, the WACCM-simulated polar Northern Hemisphere influences from the July (mid-summer) 2000 SPE were significant for a few months, but the constituent changes were not transported below about 20 hPa. However in the polar Southern Hemisphere (SH) region, the persistent downward transport in the vortex during the months of July-August-September resulted in significant modeled influences for about a year past the SPE. The SH odd nitrogen family, NO(y) (N, NO, NO2, NO3, N2O5, HNO3, HO2NO2, ClONO2, BrONO2), was greatly enhanced by this SPE and these increases were transported to the lower stratosphere. The SPE-enhanced polar NO(y) resulted in long-lasting ozone decreases (from catalytic NO(y) destruction of ozone) and ozone increases (from NO(y) interference in the chlorine and bromine catalytic ozone destruction cycles). These ozone changes resulted in simulated SH polar stratospheric temperature decreases (1-2 K) and increases (1-3 K)..

Jackman, C. H.↗
NASA NTRS1988

Effect of solar proton events in 1978 and 1979 on the odd nitrogen abundance in the middle atmosphere

Daily average solar proton flux data for 1978 and 1979 are used in a proton energy degradation scheme to derive ion pair production rates and atomic nitrogen production rates. The latter are computed in a form suitable for inclusion in an atmopheric, two-dimensional, time-dependent photochemical model. Odd nitrogen distributions are computed from the model, including atomic nitrogen production from solar protons, and are compared with baseline distributions. The comparisons show that the average effect of the solar protons in 1978 and 1979 was to cause changes in odd nitrogen only above 10 mbar and at latitudes only above about 50 deg in both hemispheres. The influence of the solar proton-produced odd nitrogen on the local abundance of odd nitrogen depends primarily on the background odd nitrogen abundance as well as the altitude and season.

Jackman, Charles H.↗
NASA NTRS2020

3D Propagation of Relativistic Solar Protons through Interplanetary Space

Context. Solar Energetic Particles (SEPs) with energy in the GeV range can propagate to Earth from their acceleration region near the Sun and produce Ground Level Enhancements (GLEs). The traditional approach to interpreting and modelling GLE observations assumes particle propagation only parallel to the magnetic field lines of interplanetary space, i.e. it is spatially 1D. Recent measurements by PAMELA have characterised SEP properties at 1 AU for the ~100 MeV-1 GeV range at high spectral resolution. Aims. We model the transport of GLE-energy solar protons using a 3D approach, to assess the effect of the Heliospheric Current Sheet (HCS) and drifts associated to the gradient and curvature of the Parker spiral. We derive 1 AU observables and compare the simulation results with data from PAMELA. Methods. We use a 3D test particle model including a HCS. Monoenergetic populations are studied first to obtain a qualitative picture of propagation patterns and numbers of crossings of the 1 AU sphere. Simulations for power law injection are used to derive intensity profiles and fluence spectra at 1 AU. A simulation for a specific event, GLE 71, is used to compare with PAMELA data. Results. Spatial patterns of 1 AU crossings and the average number of crossings are strongly influenced by 3D effects, with significant differences between periods of A+ and A- polarities. The decay time constant of 1 AU intensity profiles varies depending on the position of the observer and is not a simple function of the mean free path as in 1D models. Energy dependent leakage from the injection flux tube is particularly important for GLE energy particles, resulting in a rollover in the spectrum.

Solar energetic particles↗
NASA NTRS1975

Energetic solar proton vs terrestrially trapped proton fluxes

The relative importance of solar and trapped proton fluxes in the consideration of shielding requirements for geocentric space missions is analyzed. Using models of these particles, their fluences encountered by spacecraft in circular orbits are computed as functions of orbital altitude and inclination, mission duration, threshold energy (10 to 100 MeV), and risk factor (for solar protons only), and ratios of solar-to-trapped fluences are derived. It is shown that solar protons predominate for low-altitude polar and very high-altitude missions, while trapped protons predominate for missions at low and medium altitudes and low inclinations. It is recommended that if the ratio of solar-to-trapped protons falls between 0.1 and 10, both fluences should be considered in planning shielding systems.

King, J. H.↗
NASA NTRS1990

Effect of solar proton events on the middle atmosphere during the past two solar cycles as computed using a two-dimensional model

This paper investigates the effects of solar proton events (SPEs) on the middle atmosphere during the past two solar cycles (1963-1984), by examining changes in the production of odd nitrogen, NO(y), and ozone and using a proton energy degradation scheme to derive ion pair production rates. These calculations show that NO(y) is not substantially changed over a solar cycle by SPEs; significant SPEs last only 1-5 days, tend to occur near solar maximum, and are typically months to years apart, preventing a build up of SPE-produced NO(y). Fractional ozone changes are even smaller than the fractional NO(y) changes and are significant only for the August 1972 SPE. Ozone, like NO(y), returns to its ambient levels on time scales of several months to a year.

Jackman, Charles H.↗
NASA NTRS2014

Middle Atmospheric Changes Caused by the January and March 2012 Solar Proton Events

The recent 23-30 January and 7-11 March 2012 solar proton event (SPE) periods were substantial and caused significant impacts on the middle atmosphere. These were the two largest SPE periods of solar cycle 24 so far. The highly energetic solar protons produced considerable ionization of the neutral atmosphere as well as HOx (H, OH, HO2) and NOx (N, NO, NO2). We compute a NOx production of 1.9 and 2.1 Gigamoles due to these SPE periods in January and March 2012, respectively, which places these SPE periods among the 12 largest in the past 50 years. Aura Microwave Limb Sounder (MLS) observations of the peroxy radical, HO2, show significant enhancements of 0.9 ppbv in the northern polar mesosphere as a result of these SPE periods. Both MLS measurements and Goddard Space Flight Center (GSFC) two-dimensional (2D) model predictions indicated middle mesospheric ozone decreases of 20 percent for several days in the northern polar region with maximum depletions 60 percent as a result of the HOx produced in both the January and March 2012 SPE periods. The SCISAT-1 Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE) and the Envisat Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instruments measured NO and NO2 (NOx), which indicated enhancements of over 20 ppbv in most of the northern polar mesosphere for several days as a result of these SPE periods. The GSFC 2D model was used to predict the medium-term (months) influence and found that the polar Southern Hemisphere middle atmosphere ozone was most affected by these solar events due to the increased downward motion in the fall and early winter. The downward transport moved the SPE-produced NOy to lower altitudes and led to predicted modest destruction of ozone (5-9 percent) in the upper stratosphere days to weeks after the March 2012 event. Total ozone reductions were predicted to be a maximum of 1 percent in 2012 due to these SPEs.

ozone↗