The October 22, 1989, solar cosmic ray enhancement: An analysis of the anisotropy and spectral characteristics

Cramp, J. L.; Duldig, M. L.; Flückiger, E. O.; Humble, J. E.; Shea, M. A.; Smart, D. F.

doi:10.1029/97ja01947

Cited by 140 publications

(206 citation statements)

References 21 publications

Supporting

Mentioning

203

Contrasting

Order By: Relevance

“…Shea and Smart, 1982;Bieber and Evenson, 1995;Humble et al, 1991;Cramp et al, 1997;. It is necessary to possess information from many NM stations separated in both longitude and latitude in order to cover a wide range of cut-off rigidities and of viewing directions at the border of the geomagnetosphere.…”

Section: General Description Of the Methodsmentioning

confidence: 99%

“…Therefore, the response of each NM is computed with its own yield function corresponding to the exact altitude above the sea level. In our model the rigidity spectrum of SEPs is described by a modified power law similarly to Cramp et al (1997); Vashenyuk et al (2008):…”

Section: General Description Of the Methodsmentioning

confidence: 99%

“…In this study we employ a method developed on the basis of previous models (Cramp et al, 1997;, the details are given elsewhere (Mishev et al, 2014;Mishev and Usoskin, 2016a). The analysis of GLEs using NM data consists of several consecutive steps: (1) computation of asymptotic viewing cones and cut-off rigidity of the selected NMs by simulation of particle propagation in the magnetosphere; (2) making an initial guess of the optimization procedure (inverse problem) by assuming the apparent source position along the interplanetary magnetic field (IMF) line and/ or by application of a procedure similarly to Cramp et al (1995).…”

Section: General Description Of the Methodsmentioning

confidence: 99%

“…Shea and Smart, 1982;Cramp et al, 1997;Bombardieri et al, 2006;Mishev et al, 2014). According to the generally accepted common definition, a GLE event is registered when there is a simultaneous statistically significant increase of the count rate of at least two differently located NM stations accompanied with a statistically significant increase of the SEP flux directly observed by a spaceborne instrument(s), accordingly a sub-GLE event is registered when there are simultaneous statistically significant increase of the count rates of at least two differently located high-altitude NMs with corresponding enhancement in the proton flux measured by a space-borne instrument(s), but no statistically significant enhancement in the countrates of NMs near to the sea level .…”

Section: Introductionmentioning

confidence: 99%

“…In order to assess the SEP spectral and angular characteristics using measurements retrieved from the global NM network, it is necessary to model their propagation through the atmosphere and magnetosphere of the Earth (e.g. Shea and Smart, 1982;Humble et al, 1991;Cramp et al, 1997;Desorgher et al, 2009;. Moreover, a sufficient number of NM stations with nonnull response is necessary in order to perform an optimization procedure over a set of model parameters and experimental data similar to Cramp et al (1997); ; Mishev et al (2014).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Assessment of spectral and angular characteristics of sub-GLE events using the global neutron monitor network

Mishev

Poluianov

Usoskin

2017

J. Space Weather Space Clim.

View full text Add to dashboard Cite

-New recently installed high-altitude polar neutron monitors (NMs) have made the worldwide NM network more sensitive to strong solar energetic particle (SEP) events, registered at ground level, namely ground-level enhancement (GLE) events. The DOMC/B and South Pole NMs in addition to marginal cut-off rigidity also possess lower atmospheric cut-off compared to the sea level. As a result, the two high-altitude polar NM stations are able to detect lower energy SEP events, which most likely would not be registered by the other (near sea level) NMs. Here, we consider several candidates for such type of events called sub-GLEs. Using the worldwide NM database (NMDB) records and an optimization procedure combined with simulation of the global NM network response, we assess the spectral and angular characteristics of sub-GLE particles. With the estimated spectral characteristics as an input, we evaluate the effective dose rate in polar and sub-polar regions at typical commercial flight altitude. Hence, we demonstrate that the global NM network is a useful tool to estimate important space weather effects, e.g., the aircrew exposure due to cosmic rays of galactic and/or solar origins.

show abstract

Section: General Description Of the Methodsmentioning

confidence: 99%

Section: General Description Of the Methodsmentioning

confidence: 99%

Section: General Description Of the Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Assessment of spectral and angular characteristics of sub-GLE events using the global neutron monitor network

Mishev

Poluianov

Usoskin

2017

J. Space Weather Space Clim.

View full text Add to dashboard Cite

show abstract

Analysis of the ground level enhancement on 17 May 2012 using data from the global neutron monitor network

2014

View full text Add to dashboard Cite

We have analyzed the data of the world neutron monitor network for the first ground level enhancement of solar cycle 24, the ground level enhancement (GLE) on 17 May 2012. A newly computed neutron monitor yield function and an inverse method are applied to estimate the energy spectrum, anisotropy axis direction, and pitch angle distribution of the high‐energy solar particles in interplanetary space. The method includes the determination of the asymptotic viewing cones of neutron monitor stations through computations of trajectories of cosmic rays in a model magnetosphere. The cosmic ray particle trajectories are determined with the GEANT‐based MAGNETOCOSMICS code using Tsyganenko 1989 and International Geomagnetic Reference Field models. Subsequent calculation of the neutron monitor responses with the model function is carried out, that represents an initial guess of the inverse problem. Derivation of the solar energetic particle characteristics is fulfilled by fitting the data of the global neutron monitor network using the Levenberg‐Marquardt method over the nine‐dimensional parameter space. The pitch angle distribution and rigidity spectrum of high‐energy protons are obtained as function of time in the course of the GLE. The angular distribution appears quite complicated. It comprises a focused beam along the interplanetary magnetic field line from the Sun and a loss‐cone feature around the opposite direction, possibly indicative of the particle transport in interplanetary magnetic field structures associated with previous coronal mass ejections.

show abstract

Measurement and simulation of neutron monitor count rate dependence on surrounding structure

et al. 2015

View full text Add to dashboard Cite

Neutron monitors are the premier instruments for precise measurements of time variations (e.g., of solar origin) in the galactic cosmic ray (GCR) flux in the range of ∼1–100 GeV. However, it has proven challenging to accurately determine the yield function (effective area) versus rigidity in order to relate a neutron monitor's count rate with those of other monitors worldwide and the underlying GCR spectrum. Monte Carlo simulations of the yield function have been developed, but there have been few opportunities to validate these observationally, especially regarding the particular environment surrounding each monitor. Here we have precisely measured the count rate of a calibration neutron monitor near the Princess Sirindhorn Neutron Monitor (PSNM) at Doi Inthanon, Thailand (18.59∘N, 98.49∘E, 2560 m altitude), which provides a basis for comparison with count rates of other neutron monitors worldwide that are similarly calibrated. We directly measured the effect of surrounding structure by operating the calibrator outside and inside the building. Using Monte Carlo simulations, we clarify differences in response of the calibrator and PSNM, as well as the calibrator outside and inside the building. The dependence of the calibrator count rate on surrounding structure can be attributed to its sensitivity to neutrons of 0.5–10 MeV and a shift of sensitivity to nucleons of higher energy when placed inside the building. Simulated calibrator to PSNM count rate ratios inside and outside agree with observations within a few percent, providing useful validation and improving confidence in our ability to model the yield function for a neutron monitor station.

show abstract

The October 22, 1989, solar cosmic ray enhancement: An analysis of the anisotropy and spectral characteristics

Cited by 140 publications

References 21 publications

Assessment of spectral and angular characteristics of sub-GLE events using the global neutron monitor network

Assessment of spectral and angular characteristics of sub-GLE events using the global neutron monitor network

Analysis of the ground level enhancement on 17 May 2012 using data from the global neutron monitor network

Measurement and simulation of neutron monitor count rate dependence on surrounding structure

Contact Info

Product

Resources

About