Correlation of solar energetic protons and polar cap absorption

Patterson, J. D.; Armstrong, T. P.; Laird, Claude M.; Detrick, D. L.; Weatherwax, A. T.

doi:10.1029/2000ja002006

Cited by 45 publications

(52 citation statements)

References 14 publications

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“…The exponent of 1.5 is based on J. K. Hargreaves's analysis of multi-frequency absorption measurements by Parthasarathy et al (1963) and agrees with exponents from 1.4 to 1.6 presented in Figure 10 of Patterson et al (2001) which were determined from three SPEs in 1989 and1990. Whilst these measurements are based on daytime events, we follow (Sauer & Wilkinson 2008) in also adopting the 1.5 exponent during nighttime measurements.…”

Section: Riometer Measurementsmentioning

confidence: 89%

“…The profile is broadly exponential with distinct scale heights of h E~5 1 km in the E-region (90-120 km) (Vickrey et al 1982), and h Dd~6 .1 km and h Dn~4 .3 km in the day and night D-region, respectively (Gledhill 1986). These profiles, which were applied in the PCA model of Patterson et al (2001), are best-fit values from observations that can range over several orders of magnitude at 50 km altitude. It will be shown in Section 3 how the D-region scale heights h Dd and h Dn may be used as variable parameters of the model which can be optimised by regression to riometer measurements.…”

Section: Type 2 (Full-profile) Pca Modelsmentioning

confidence: 99%

“…where q 0 (E, z) is the rate of ionisation at altitude, z, as a function of the energy incident at the top of the ionosphere, E, and is determined (following Patterson et al 2001) from measurements of the proton energy loss rate (eV m À1 ) at sea level (Janni 1966; Eq. (4) of Patterson et al 2001), modified by height profiles of atmospheric density relative to that at sea level (using the NRLMSISE-00 model) and using an assumption that each generated electron-ion pair results in the energetic proton losing 1/35 eV (Porter et al 1976).…”

Section: Type 2 (Full-profile) Pca Modelsmentioning

confidence: 99%

“…oJ(E)/oE is the differential isotropic proton flux (pfu MeV À1 ) measured by a near-Earth satellite such as GOES. Following Patterson et al (2001), the factor of 2p 3 (sr) in Eq. (12) is the effective solid angle of proton flux propagating in the downward direction assuming an isotropic angular distribution at the satellite.…”

Section: Type 2 (Full-profile) Pca Modelsmentioning

confidence: 99%

“…(4) of Patterson et al 2001), modified by height profiles of atmospheric density relative to that at sea level (using the NRLMSISE-00 model) and using an assumption that each generated electron-ion pair results in the energetic proton losing 1/35 eV (Porter et al 1976). oJ(E)/oE is the differential isotropic proton flux (pfu MeV À1 ) measured by a near-Earth satellite such as GOES.…”

Section: Type 2 (Full-profile) Pca Modelsmentioning

confidence: 99%

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Assimilation of real-time riometer measurements into models of 30 MHz polar cap absorption

Rogers

Honary

2015

J. Space Weather Space Clim.

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Space weather events may adversely affect high frequency (HF) radio propagation, hence the ability to provide nowcasting and forecasting of HF radio absorption is key for industries that rely on HF communications. This paper presents methods of assimilating 30 MHz radio absorption measurements into two types of ionospheric polar cap absorption (PCA) model to improve their performance as nowcasting tools. Type 1 models calculate absorption as m times the square root of the flux of solar protons above an energy threshold, E t . Measurements from 14 riometers during 94 solar proton events (1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010) are assimilated by optimising the day and night values of m by linear regression. Further non-linear optimisations are demonstrated in which parameters such as E t are also optimised and additional terms characterise local time and seasonal variations. These optimisations reduce RMS errors by up to 36%. Type 2 models incorporate altitude profiles of electron and neutral densities and electron temperatures. Here the scale height of the effective recombination coefficient profile in the D-region is optimised by regression. Furthermore, two published models of the rigidity cut-off latitude (CL) are assessed by comparison with riometer measurements. A small improvement in performance is observed by introducing a 3-h lag in the geomagnetic index K p in the CL models. Assimilating data from a single riometer in the polar cap reduces RMS errors below 1 dB with less than 0.2 dB bias. However, many highlatitude riometers now provide absorption measurements in near-real time and we demonstrate how these data may be assimilated by fitting a low-order spherical harmonic function to both the measurements and a PCA model with optimised parameters.

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Section: Riometer Measurementsmentioning

confidence: 89%

Section: Type 2 (Full-profile) Pca Modelsmentioning

confidence: 99%

Section: Type 2 (Full-profile) Pca Modelsmentioning

confidence: 99%

Section: Type 2 (Full-profile) Pca Modelsmentioning

confidence: 99%

Section: Type 2 (Full-profile) Pca Modelsmentioning

confidence: 99%

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Assimilation of real-time riometer measurements into models of 30 MHz polar cap absorption

Rogers

Honary

2015

J. Space Weather Space Clim.

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Dynamics of the correlation between polar cap radio absorption and solar energetic proton fluxes in the interplanetary medium

et al. 2014

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During solar energetic particle (SEP) events, large fluxes of energetic particles spreading throughout the interplanetary medium (IPM) have access to the upper polar atmosphere where they play important roles in physical and chemical processes. We examine the dynamics of the relation between solar energetic proton (SEP) fluxes detected outside the magnetosphere by SOHO, at geosynchronous orbit by GOES 8, and in low earth orbit by NOAA 15 (POES) satellites on one hand, and ionospheric absorption measured by a NORSTAR riometer in the polar cap on the other. We attempt to isolate SEP-related signals by rejecting periods influenced by electron precipitation and solar radio bursts. Under these conditions we find R 2 of up to 0.9 between the logarithms of SEP flux and absorption for all satellites, but with the additional restriction to periods beginning 10 h after event onsets and within tens of hours following times of maximum flux. We find that the flux-absorption correlation is poor during the first few hours of an event, which we attribute to the fact that SEP angular distributions are often highly peaked along the interplanetary magnetic field during the early stages of an event. Such highly anisotropic distributions map to small regions inside the polar caps, making it unlikely that the corresponding absorption signal will be detected by a single riometer. These observations suggest that riometers in combination with a suitable numerical tool can be used as a diagnostic of properties of energetic proton populations in the interplanetary medium.

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Influence of dust loading on atmospheric ionizing radiation on Mars

2014

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Measuring the radiation environment at the surface of Mars is the primary goal of the Radiation Assessment Detector on the NASA Mars Science Laboratory's Curiosity rover. One of the conditions that Curiosity will likely encounter is a dust storm. The objective of this paper is to compute the cosmic ray ionization in different conditions, including dust storms, as these various conditions are likely to be encountered by Curiosity at some point. In the present work, the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety model, recently modified for Mars, was used along with the Badhwar & O'Neill 2010 galactic cosmic ray model. In addition to galactic cosmic rays, five different solar energetic particle event spectra were considered. For all input radiation environments, radiation dose throughout the atmosphere and at the surface was investigated as a function of atmospheric dust loading. It is demonstrated that for galactic cosmic rays, the ionization depends strongly on the atmosphere profile. Moreover, it is shown that solar energetic particle events strongly increase the ionization throughout the atmosphere, including ground level, and can account for the radio blackout conditions observed by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument on the Mars Express spacecraft. These results demonstrate that the cosmic rays' influence on the Martian surface chemistry is strongly dependent on solar and atmospheric conditions that should be taken into account for future studies.

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Correlation of solar energetic protons and polar cap absorption

Abstract: Abstract.This

Cited by 45 publications

References 14 publications

Assimilation of real-time riometer measurements into models of 30 MHz polar cap absorption

Assimilation of real-time riometer measurements into models of 30 MHz polar cap absorption

Dynamics of the correlation between polar cap radio absorption and solar energetic proton fluxes in the interplanetary medium

Influence of dust loading on atmospheric ionizing radiation on Mars

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